Permitting and Inspecting
PV Systems
PV 403
Created and Written by: Kelly Provence
Permitting and Inspecting PV Systems
PV 403
Part 1
Permitting Solar PV Systems
Created and Written by: Kelly Provence
1
SOLAIRGEN
School of Solar technology
Founded in 2002
www.solairgen.com
119 Highway 52 West
Dahlonega, GA 30533
706-867-0678
info@solairgen.com
Kelly Provence
IREC Certified Master Trainer
NABCEP Certified PV Installation Professional
NABCEP Certified PV Technical Sales
Licensed Master Electrician
2
Table of Contents
Permitting Solar PV Systems
Solar energy, PV cells, modules and arrays
PV array physical installation methods and concerns
Residential PV system types and function
Interactive systems
Micro-inverter and string inverter systems
PV systems with energy storage
Example permit forms for residential
Commercial interactive PV inverters and systems
Example permit forms for commercial
Labels, plaques and placement
Important components of permitting PV systems
Inspecting Solar PV Systems
Roof access and physical installation parameters
Review and most common violations
PV systems and the NEC
Significant changes from 2014 to 2017 editions
PV system grounding
Review and most common violations
Grounding electrode requirements
Review and most common violations
Voltage limits and calculations
Conductor properties and selection
Voltage drop calculations
Overcurrent protection requirements
Review and most common violations
Conductor protection
Review and most common violations
Arc protection and first responder safety requirements
Review and most common violations
Disconnect requirements
Review and most common violations
Label and plaque requirements
Review and most common violations
Interactive system utility connection
Review and most common violations
Label and plaque example layout drawings
Addendum: Energy storage systems
Requirements for all battery systems
Review and most common violations
Energy storage systems operating over 60v
Review and most common violations
Label and plaque example layout drawings
6
17
25
29
33
44
55
71
78
83
87
92
105
107
109
113
121
124
132
3
134
139
152
156
163
166
172
174
183
185
196
199
209
211
223
225
229
231
237
239
251
254
4
Key Terms
Photovoltaic (PV) also Solar Electric: The conversion of photon energy (light) into
electron energy (electricity).
Inverter: A device that converts DC electrical energy to AC electrical energy.
Interactive inverter: An inverter that produces electricity in parallel with the utility
electricity.
Stand alone inverter: An inverter that creates its own waveform and AC electricity
from stored energy such as a battery.
Multimodal inverter: An inverter that can function as interactive or stand alone.
National Electrical Code NEC: A published advisory guide by the NFPA for safe
electrical installations. It is placed into law by states and other jurisdictions.
The 2014 NEC is now in effect for most states in the U.S.
Authority Having Jurisdiction (AHJ): An organization, office, or individual responsible
for enforcing the requirements of a code or standard, or for approving equipment,
materials, an installation, or a procedure.
5
The Solar Source
Traveling at the speed of 186,000 miles per second (300,000 kilometers per second), radiation
from the sun takes more than 8 minutes to reach Earth’s surface.
At any instant, Earth receives approximately 170 million Gigawatts of power from the sun.
The visible light is one portion of radiation that reaches earth. Ultraviolet, infrared and radio
waves make up the other portions of non-visible light.
6
Electron Movement and Speed
Upon striking the surface of the PV cell, photon energy is converted to electron energy.
• A fraction of a second later it is used by an electrical appliance.
• The conversion process (a band-gap magnetic field conversion) nets only about 16% to
21% of the photon energy into electron energy.
− 30% will be the maximum for this type of process.
Sunlight energizes electrons
within the solar cell. Potential
energy is created on the
negative side of the cell.
When an electrical load is
connected in between the
negative and positive contacts,
electrical energy is delivered to
the load.
7
Mono-crystalline silicon ingots are grown in single crystal cylinders.
Over a period of hours, the molten silicon is grown to be a large cylindrical crystal up to 40″
in length and up to 8″ in diameter (5” and 6” for PV cells).
•
The ingot is a single uniform crystal.
•
The ingots are cut into wafers about 180μm thick.
•
The cells are doped to create a positive and negative side.
• An antireflective coating is
applied.
• Electrical contacts are
imbedded and soldered into the
surface.
8
PV Modules
Cells are soldered to each other in series, negative to positive (front to back).
• Voltage per cell is about .5 to .6 volts when operating.
• Current per cell is dependent on its size (5” ≈ 6amps) (6” ≈ 8.5amps)
60 - 6” monocrystalline cells
31.6v x 8.7a = 275w
72 - 5” monocrystalline cells
37.8v x 6.1a = 230w
60 - 6” polycrystalline cells
30.7v x 8.3a = 255w
9
PV Module Test Conditions
STC (standard test condition) uses 1000W/m²at 25°C cell temp.
All systems are designed using STC data.
NOC (normal operating conditions) uses 800W/m² at NOCT at 20°C ambient temp.
(Cell temperature is 45° to 48°C)
Voltage and current are lower with NOC than STC. It is provided to give a more
realistic operating condition when the module is installed
Back to
slide 152
10
1000W/m² 25C
 The PV system is built from the
module data tested at Standard
Test Condition (STC).
 Deviations in voltage are
calculated for extreme
temperatures using temperature
coefficients (TC) provided for
Voc and Pmax.
46C
11
Typical residential interactive system – 1 sting of 13 in series (maximum)
Module
Max Power (Pmax)
Volts (Vmp)
Current (Imp)
Open Volt (Voc)
SC Current (Isc)
300 watts
31.6 volts
9.57 amps
40.1 volts
10.23 amps
x 13
x 13
x 1
x 13
x 1
=
=
=
=
=
System
Pmax
Vmp
Imp
Voc
Isc
3,900 watts (3.9kW)
410.8 volts
9.57 amps
521.3 volts
10.23 amps
12
Typical residential interactive system – 1 sting of 8 in series (minimum)
Module
Pmax
Vmp
Imp
Voc
Isc
300 watts
31.6 volts
9.57 amps
40.1 volts
10.23 amps
x
x
x
x
x
8
8
1
8
1
=
=
=
=
=
System
Pmax
Vmp
Imp
Voc
Isc
1 string
2,400 watts (2.4 kW)
252.8 volts DC
9.57 amps
320.8 volts
10.23 amps
SolarEdge inverters with module level power electronics (MLPE), can control from 8 to 25
of their MLPE optimizers in a single string.
13
2 strings of 8 modules in series
Module
Pmax
Vmp
Imp
Voc
Isc
300 watts
31.6 volts
9.57 amps
40.1 volts
10.23 amps
x 16 =
x 8 =
x 2 =
x 8 =
x 2 =
System
Pmax
Vmp
Imp
Voc
Isc
2 strings
4,800 watts (4.8 kW)
252.8 volts DC
19.14 amps
320.8 volts
20.46 amps
14
Micro-inverters: The system voltage and amperage are AC.
Module
Pmax
Vmp
Imp
Voc
Isc
Inverter
Each
300 watts
31.6 volts
9.57 amps
40.1 volts
10.23 amps
250 watts
240 volts
1 amps
x 8 =
x 1 =
x 8 =
System
Total
2kW AC
2.4kW DC
240 volts AC
8 amps AC
15
-
-
-
+
+
+
-
-
-
Low voltage system (battery based – 3 strings of 3 in series)
-
Module
Pmax
Vmp
Imp
Voc
Isc
-
300 watts
31.6 volts
9.57 amps
40.1 volts
10.23 amps
x9
x3
x3
x3
x3
+
+
+
-
+
+
+
+
Load
=
=
=
=
=
System
Pmax
Vmp
Imp
Voc
Isc
2,700 watts (2.7kW)
94.8 volts
28.71 amps
120.3 volts
30.69 amps
16
Steep Roof Mounts are typical for residential PV arrays.
The modules are attached to rails that are attached to stand-offs that are bolted to the roof.
• This mounting method accounts for over 98% of residential rooftop installations.
17
Standing seam roofs can accommodate an alternate PV product that is directly
attached to the metal roof.
• These thin-film PV modules have an adhesive for direct attachment.
• These account for a very small portion of roof mounted PV arrays (2003 to 2011).
− Less than 1% of residential rooftop installations
18
PV roofing shingles are installed in place of standard shingles.
•
The higher cost and specific training requirements has limited its success.
•
These installations are seen in U.S. states with incentives and high electrical rates.
•
CertainTeed and Dow currently have these products available in a few locations.
•
These account for less than 1% of residential rooftop installations
− However Elon Musk says his products are the future of residential rooftop solar.
Product available in these states
19
Single pole mounts are a good where there is enough room.
Optimum azimuth and array tilt can be attained.
• The array can be placed away from solar obstructions and the modules will operate at a
lower temperature than roof mounted modules.
• Off grid systems should be pole mounted to optimize year-round performance.
− Close to 50% of rural residential PV systems are ground mounts.
− The figure is much lower in metropolitan areas.
20
Access to the Roof
Residential PV Array Pitched Roof Access
The modules are installed parallel to the roof so energy density is maximized.
• There should be roof access for other contractors and first responders.
• 3’ to the sides and top should be minimum for access.
 The fire marshal is most concerned with these margins.
21
Physical Installation Concerns
Dead Loads. The weight of materials of construction incorporated into the building,
including but not limited to roofs, the weight of fixed service equipment, such as
plumbing stacks and risers, electrical feeders, heating, ventilating and air-conditioning
systems, and solar installations.
•
•
Minimum dead load rating are 10 lb.ft²
−
PV array directly attached parallel to roof add less than 4lb/ft²
−
Standard roofing material including decking weighs less than 4lb/ft²
The only time a standard residential roof top installation will be a weight problem
is if there is already a problem with the dead load limit.
Environmental loads. Wind load, snow load, rain load, earthquake load, flood load.
Wind loads are the primary concern for southern U.S. states.
•
Racking manufacturers provide white paper on wind lift tests with their equipment
for 90 mph and 120 mph.
•
Most of Georgia is 90mph wind zone with the coast and northern mountains above
3000’ being the exception.
22
Attachment on Steep Sloped Roofs (greater than 3/12 pitch).
Lag screws are the most common type of
fastener used to attach array mounting
systems to wood structures, usually
residential roofs.
•
Calculate withdrawal strength
•
Pre-drill hole 2/3 screw diameter
•
Use butyl caulk and flashing
Composite shingle
Bronzed for shake or composite
23
Direct Attachment
Asphalt shingle roofs can be sealed with direct attachment
Butyl tape allows for the rail-less direct attachment.
•
The butyl tape is placed below the attachment and
Self-seals when neoprene washer screws are used
to attach to the roof.
Roof Tech
24
Residential PV System Types and Function
In application there are three types of solar PV systems that we use.
1.
2.
Utility Interactive also known as Grid Tied or On-Grid
•
The PV array DC energy is fed into the inverter that converts DC to AC. The
energy is supplied to the AC loads and out to the grid.
•
When the utility power is down so is the PV inverter output.
Stand Alone Off-Grid battery based
•
The PV array charges the batteries and the inverter uses the stored battery energy
to supply the premise’s loads.
−
3.
A back up generator is also required.
Bi-Modal or Multimodal battery based and grid interactive
•
This system can operate in several different modes as the name suggests.
−
Utility Interactive
−
Net Zero or Self Consumption
−
Stand Alone
25
PV System Safety Compliance Requirements
• DC Voltage is limited to 600v. PV voltage rises with cold temperatures so this must be
calculated using ASHRAE minimum mean temperature.
− Micro-inverters control this; others require the installer to control it.
• Rapid shutdown for first responders. Rooftop PV arrays must reduce voltage 1’ outside
the array boundary to 30v in 10 seconds when the rapid shutdown device is activated.
− Micro-inverters and SolarEdge control this; others require the installer to install it.
• Anti-islanding UL1741 listed inverters. The inverter must stop sending power into the
grid during an outage.
− Included in all UL 1741 listed inverters
• GFDI equipped. The system must have ground fault detection on the PV array DC circuit
that detects ground faults and shuts down equipment connected to the array if detected.
− Included in all interactive inverters; installer provides this with battery systems.
• AFCI equipped. The system must have arc-fault detection on the PV array DC circuit that
detect arcs from the array and shuts down equipment connected to the array if detected.
− Included in all interactive inverters; installer provides this with battery systems.
26
Example Layout Diagram Submitted with Permit Application
This diagram provides the inspector with locations of all equipment.
27
Example Three Line Diagram
The flow of electrical current provide a simple way to see all components in the system and
details of the conductus and conduit.
The line diagrams should show:
•
Specifications of the PV equipment.
•
The location of disconnects
•
The voltage and amperage of all circuits.
•
Rating and location of overcurrent devices
•
Equipment conductor ratings
•
Capacity of service equipment
•
The IEEE1547 and UL1741 compliance.
28
Utility Interactive Inverters
There are three main types of utility interactive inverters.
Micro inverters: These attach to each module and convert the single module DC energy to
utility AC voltage (240v or 208v AC) (22v – 48v DC)
• One module per inverter.
• Some commercial micro-inverters allow 2 to 4 modules per inverter.
String inverters: A string inverter consists of a number of modules connected in series with 1
to 10 identical strings connected in parallel.
• Residential string inverters are usually 2kW to 10kW rated (1 – 4 strings)
− (240v AC)
(150v – 600v DC)
String inverters with optimizers: Same as standard string inverter except each module has an
optimizer connect directly to the module DC output.
• The optimizer is a DC to DC conversion device that improves performance and can
reduce voltage to a safe level when AC power is disconnected at the inverter.
− (240v AC)
(8v – 600v DC)
29
Utility Interactive PV System
Using micro-inverters
Micro-inverter
The flow of electrical energy
is one-way up to the AC
utility connection point
AC Power
30
Utility Interactive PV System
Using string inverter
Rapid Shutdown device
Rapid Shutdown
switch
DC
Disconnect
31
Utility Interactive PV System
String inverter with PV optimizers
PV Optimizes
DC
Disconnect
32
Micro Inverters
Each module has its own inverter. The inverter is mounted
on the rail underneath the module.
• Some PV modules have the inverter built into the
module j-box (AC module)
• 15 to 21 of these inverters can be connected together
before connecting to a back-feed AC breaker.
• AC output conductors are ran in PVC or metal conduit.
Inverter AC power is disconnected
when the inverter disconnect or
main house power is turned off.
Module DC power is reduced to the
single module power at the microinverter when the AC power is
turned off.
Inverter AC disconnect
33
Micro-inverter Disconnect and Rapid shutdown
The Utility AC disconnect is also the main system AC disconnect and Rapid shutdown
(AC)
3) PV array AC Disconnect
Utility accessible / Rapid Shutdown
4) Main house AC meter/disconnect
3
4
The PV array AC disconnect serves three functions:
a) Servicing AC disconnect
b) Utility AC disconnect
c) Rapid shutdown system disconnect
34
Single line diagram: Interactive system with micro-inverters
1. PV module data
Pmax ____
Voc
____
Vmp ____
Isc
____
Imp
____
3. Conductor data
AWG ____
Qty
____
EGC ____
Conduit
Type ____
Size ____
2. Inverter data
Watts ____
Volts ____
amps ____
System
Circuit amps ____
# of circuits ____
4. AC disconnect
Labels
Volts ____
Amps ____
Rapid shutdown
6. Interconnection ratings
Service
____a
Busbar
____a
Main OCD
____a
Inverter OCD ____a
5. Conductor data
AWG ____
Qty
____
EGC ____
Conduit
Type ____
Size ____
____
35
Layout diagram: Roof mounted array with micro-inverters
+
+
+
There is no DC
potential. 1
1
J-box
+
+
AC Panel
1234kWH
+
2
PV array
Meter
PV system
AC disconnect 2
Rapid shutdown
is provided via
AC disconnect.
Garage
Red line is DC circuit
Blue line is AC circuit (interactive)
Driveway
36
Residential String Inverters
The string inverter is usually located on
the exterior wall of the house or it is
located in the garage or basement.
• Most utilities require the AC
disconnect to be on the exterior.
• The 2017 NEC requires the rapid
shutdown device to be on the exterior
2017 Rapid Shutdown device location
2014 device may be as far as 10’ away
High DC voltage exists from the array to
the inverter during operation.
• The DC voltage is usually between
150v and 500volts.
• The conductors must be in metal
conduit if ran inside.
• The conduit must be marked
“PV SOURCE CIRCUIT”
Rapid shutdown switch may be DC and/or AC.
Inverter AC disconnect
37
String Inverters with PV Optimizers
Performance, safety and monitoring are enhanced with
module level PV optimizers.
• The location of this inverter and AC disconnect is
the same as the string inverter.
• The PV optimizer functions as the rapid shutdown
device during a power outage or when the AC or
DC switch is turned off.
High DC voltage exists from the array to the inverter
during operation.
• The DC voltage is between 150v and 500volts.
• The conductors must be in metal conduit if ran
inside.
• The conduit must be marked
“PV SOURCE CIRCUIT”
Rapid shutdown switch may be DC and/or AC.
Inverter AC disconnect
38
String Inverter Disconnect and Rapid Shutdown
With the SolarEdge systems, #2 is simple a j-box.
With a standard string inverter, #2 is the Rapid Shutdown device activated by #3 or #5.
Rapid Shutdown device
/ Rapid Shutdown switch
5
33
6
Main house AC meter/disconnect
 Ground mounted PV arrays with the DC disconnect located at the array or the
exterior of the home are not required to have a rapid shutdown system.
39
Single line diagram: Interactive system with string inverters
1. PV module data
Pmax ____
Voc
____
Vmp ____
Isc
____
Imp
____
3. DC disconnect
Label
Max volts
____
Max amps
____
Rapid shutdown ____
5. AC disconnect
Label
Volts ____
Amps ____
Rapid shutdown ____
2. Conductor data
AWG ____
Qty
____
EGC ____
Conduit
Type ____
Size ____
4. Inverter
Watts ____
Volts ____
amps ____
System
Circuit amps ____
# of circuits ____
6. Conductor data
AWG ____
Qty
____
EGC ____
Conduit
Type ____
Size ____
6. Interconnection ratings
Service
____a
Busbar
____a
Main OCD
____a
Inverter OCD ____a
40
Layout diagram: Roof mounted array with string inverter
+
+
+
J-box
DC disconnect 1
1
AC disconnect 2
Inverter
Potential high voltage DC crosses
roof top of interior
of structure.
+
+
+
Potential is the
DC circuit from
PV array to DC
disconnect.
2
PV array
1234kWH
AC Panel
Rapid shutdown
is at 1 and/or 2
Meter
Garage
Red line DC
Blue line AC
Red line is DC circuit
Driveway
Blue line is AC circuit (interactive)
41
Layout diagram: Roof mounted array with string inverter (remote disconnect)
+
+
+
Potential high voltage DC crosses
roof top of interior
of structure.
PV array DC
disconnect 1
J-box
+
+
+
2
PV array
Meter
Inverter
AC Panel
1234kWH
1
The Inverter AC
disconnect 2
Garage
Directional plaque for
inverter AC disconnect
Rapid shutdown
is required at 2
or by separate
listed device.
Red line is DC circuit
Blue line is AC circuit (interactive)
Driveway
42
Layout diagram: Ground mounted array
+
+
+
+
+
1
+
Inverter
PV array
2
DC disconnect 1
1234kWH
AC Panel
Meter
Garage
AC disconnect 2.
There is no DC
potential inside
the house.
Rapid shutdown
is not required
Red line is DC circuit
Blue line is AC circuit (interactive)
Driveway
43
PV Systems with Energy Storage
Stand Alone and Multimodal: Both are designed to operate as Stand alone.
Stand alone systems can be a combination of DC and AC circuits or AC only.
Multimodal systems include AC circuits and can also operate in several other modes.
• Grid interactive (sells excess energy into the grid during high irradiance hours)
• Grid assisted stand alone (grid acts as a backup generator)
• Grid use mode (uses the grid to support loads during a specified time)
• Net Zero mode (meters usage so that minimal power is bought or sold to the grid)
Self Consumption: This is a single inverter interactive system with energy storage.
It is designed for a 24 hour period to prevent selling power into the utility grid.
i.e. “ The PowerWall”
• Some also operate in stand-alone mode for a short period of time.
• Multimodal inverters that operating in this mode refer to it as “Net Zero”.
44
Stand Alone or Bimodal PV System
DC COUPLED
CRITICAL AC LOADS
Input only
OR UTILITY CONNECTION
Backup power sources
45
PV System with Energy Storage
DC coupled PV system with energy storage and inverter inside the structure.
(DC or AC)
3) PV array DC or AC Disconnect
and / Rapid Shutdown
6
4
5
3
7
Battery bank
disconnect inside.
4) Critical loads AC disconnect:
inverter located inside
5) Plaque: Directory to all PV system
and battery disconnects not located
within site of the service meter.
6) Battery bank disconnect located
inside the structure.
7) Main house AC meter/disconnect
Three disconnects are required to shut down all electrical components:
4) Shuts down the PV array
5) Shuts down the critical backup AC loads
6) Shuts down the DC energy from the battery bank
46
Single line diagram: Multimodal PV system DC coupled
Since there are many more components with a battery system, it may be better to identify the
products and circuits on this page with a subsequent page listing the details of the system.
• Arrows can be used to show the flow of energy during operation as well.
Stand Alone or Bimodal PV System
AC COUPLED
PV power is fed through an
interactive inverter into the
critical loads AC panel.
DC
DISCONNECT
AC DISTRUBUTION
CENTER
INTERACTIVE
INVERTER
CRITICAL AC LOADS
Input only
OR UTILITY CONNECTION
The battery inverter must control the
interactive inverter’s power output when the batteries are fully charged.
48
PV System with Energy Storage
AC coupled PV system with energy storage and battery inverter inside the structure.
(DC or AC)
3) PV array DC or AC Disconnect
and / Rapid Shutdown
7
Battery bank
disconnect inside.
6
5
4
3
4) Interactive inverter
8
5) Critical loads AC disconnect:
inverter located inside
6) Plaque: Directory to all PV system
and battery disconnects not located
within site of the service meter.
7) Battery bank disconnect located
inside the structure.
8) Main house AC meter/disconnect
5) Shuts down the PV array
6) Shuts down the critical backup AC loads
7) Shuts down the DC energy from the battery bank
49
Single line diagram: Multimodal PV system AC coupled
NOTE: Three line diagrams are sometime required with residential systems even though they
don’t usually provide any useful information.
Exception: Ground mounted PV arrays require a ground electrode system.
• This being the case a three line diagram would be helpful or at least a one diagram with
grounding shown.
Layout diagram: Multimodal PV system with energy storage in basement
Preferred location for
PV DC disconnect
+
+
+
+
Batteries and Stand-alone
inverter located in basement
Interactive
AC disconnect
3
3
Preferred
location
PV array
Directional plaque for
inverter AC disconnect
Stand-alone
AC disconnect
(only required to be
readily accessible)
AC Panel
AC Panel
Stand
alone
Main
2
DC circuit
disconnects 1
Interactive AC
disconnect 2
1234kWH
Battery
inverter
1
+
+
+
+
+
+
+
DC Panel
&OCDs
AC Panel
&OCDs
+
+
Charge
controller
+
1
Battery bank
Meter
Stand-alone AC
disconnect 3
Garage
Red line is DC circuit
Blue line is AC circuit (interactive)
Driveway
Green line is AC circuit (stand-alone)
51
Layout diagram: Multimodal PV system with energy storage in garage
Preferred location for
PV DC disconnect
1
DC circuit
disconnects 1
Potential high voltage DC crosses
roof top of interior of structure.
+
+
+
Stand-alone AC
disconnect 3
PV array
DC Panel
&OCDs
Battery
inverter
AC Panel
&OCDs
1
AC Panel
AC Panel
Stand
alone
Main
3
Meter
1234kWH
+
+
+
Interactive AC
disconnect. 2
2
+
+
+
+
+
+
+
+
Garage
Red line is DC circuit
Blue line is AC circuit (interactive)
Green line is AC circuit (stand-alone)
Driveway
Directional plaque for
Stand-alone inverter AC
disconnect
52
Layout diagram: Multimodal PV system with energy storage in garage
+
+
+
+
+
+
1
PV array
PV array DC
disconnect 1
Battery
inverter
AC Panel
&OCDs
AC Panel
AC Panel
Stand
alone
Main
3
Meter
Interactive AC
disconnect 2
1234kWH
DC Panel
&OCDs
2
+
+
+
+
+
+
+
+
Garage
Stand-alone AC
disconnect 3
Red line is DC circuit
Blue line is AC circuit (interactive)
Driveway
Green line is AC circuit (stand-alone)
Directional plaque for
Stand-alone inverter AC
disconnect
53
PV-Direct Stand alone and bimodal (Self-consumption)
A single inverter located inside or outside
functions as AC coupled interactive and
standalone inverter.
Critical Loads
Main Loads
54
Example Layout Diagram Submitted with Permit Application
This diagram provides the inspector with locations of all equipment.
55
Permit information pertaining to the Residential PV system
Select one in each category
Page 1a
 Roof mount
 Roof has adequate dead load rating for addition of PV array
 Roof dead load rating is unverified
Roof attachment:
 Flashed attachment
 Direct attachment with butyl and polyurethane sealant
 Other – specify _______________________________________________________
Railing and module attachment
 Manufactured railing system with integrated grounding
 Other – specify _______________________________________________________
First responder and service access
 3’ access has been provided from roof ridge and one side of roof
 Access is provided from a separate roof access direction and plane.
56
Select one in each category
Page 1b
 Ground mount
Grounding electrode system: ____________________________________________
 Auxiliary electrode system
 Bonded to premises electrode system
Grounding electrode conductor GEC) size ______AWG
Source conductor protection
 Elevation _____FT above ground
 Fence _____FT high _____FT away from array
 Barrier – describe____________________________________________________
57
Page 2a
 Interactive – Micro-inverters
Module name __________
# of inverters ______
ID name__________
watts _______
rating kW_____
Qty _____
Inverter AC circuit rating ______a
Inverter AC circuit output ______AWG OCD _____a
PV system rating DC ______kW
□ UL1741
# of AC circuits ______
EGC size _______AWG
AC rating ______kW
Inverter AC output connection information:
 Backfed breaker connection in AC load center
Ampacities: Busbar _____a
Main OCD _____
Inverter OCD(s) _____a
 Tap on load side of meter: Service feeders _____a
Inverter OCD(s) _____a
 Line side connection:
Inverter OCD(s) _____a
AC disconnect label:
Rapid shutdown:
Service feeders _____a
Operating voltage ______v
□ AC disconnect
Operating current ______a
□ N/A
58
Layout Diagram with Labels (Interactive – Micro-inverters)
Place numbers by associated equipment location
Location list
1. Driveway at structure
2. Service meter
3. Main AC load center
4. PV array w/micro-inverters
5. Inverter AC disconnect/
Rapid shutdown switch + label
6. Inverter interconnection point + label
59
Page 2b
 Interactive – String inverter(s) ID name__________
Module name __________
watts_______
Max PV array DC voltage ______v
rating kW_____
Qty ____
□ UL1741
# in series _____
e.g. Voc x (1+(((C-(+25C)) x TCVoc)
 Controlled by inverter/PV optimizer
Max PV array DC current ______a
e.g. Isc x 125% x # strings in parallel
PV output circuit to inverter ______AWG
EGC size _______AWG
Inverter AC circuit output ______AWG OCD _____a
# of inverter circuits _______
EGC size _______AWG
PV system rating DC ______kW
AC ______kW
Inverter AC output connection information:
 Backfed breaker connection in AC load center
Ampacities: Busbar _____a
Main OCD _____
Inverter OCD(s) _____a
 Tap on load side of meter: Service feeders _____a
Inverter OCD(s) _____a
 Line side connection:
Inverter OCD(s) _____a
Service feeders _____a
DC disconnect label:
Max voltage ______v
AC disconnect label:
Operating voltage ______v
Rapid shutdown:
□ AC disconnect
Max current ______a
Operating current ______a
□ DC disconnect
□ Actuator
□ N/A
60
Layout Diagram with Labels (Interactive – String inverters)
Place numbers by associated equipment location
Location list
1. Driveway at structure
2. Service meter
3. Main AC load center
4. PV array
5. Rapid shutdown device
6. PV array DC disconnect + label
7. Interactive inverter
8.
Inverter AC disconnect/
Rapid shutdown switch + label
Inverter interconnection point + label
9.
61
Page 2c
 Stand Alone – DC coupled
Module name __________
watts _______
Max PV array DC voltage ______v
Qty _____
e.g. Voc x (1+(((C-(+25C)) x TCVoc)
 Controlled by PV optimizer
Max PV array DC current ______a
e.g. Isc x 125% x # strings in parallel
PV output circuit to controller ______AWG
EGC size _______AWG
Charge Controller (CC) rating kW _____________
Controller DC circuit output ______AWG
OCD _____a
Battery Inverter name __________
rating kW_________
PV system rating DC ______kW
AC rating ______kW
EGC size _______AWG
Qty _____
□ UL1741
Battery type FLA, VRLA, Salt water, Li-ion, other ________________
Battery bank voltage ______v
capacity________kWh
Batter bank Isc ______
Battery bank disconnect label:
Nominal battery bank voltage ______
Max battery bank Isc _______
Arc clearing time for OCD ______
Date the calculation ______
62
DC disconnect label:
Max voltage ______v
Rapid shutdown:
Max current ______a
□ DC disconnect
Inverter AC output label:
□ Actuator
Max CC current _____a
□ N/A
Operating voltage ______v
Operating current ______a
63
Layout Diagram with Labels (Stand-alone – DC coupled)
Place numbers by associated equipment location
Location list
1. Driveway at structure
2. Service meter
3. Main AC load center
4. PV array
5. Rapid shutdown device
6. PV array DC disconnect + label
7. Charge controller
8.
9.
10.
11.
Battery bank with disconnect + label
Battery inverter
Inverter AC disconnect + label
Directory to all electrical power sources
64
Page 2d
 Multi-modal – DC coupled
Module name __________
rating _______watts
Max PV array DC voltage ______v
Qty _____
e.g. Voc x (1+(((C-(+25C)) x TCVoc)
 Controlled by PV optimizer
Max PV array DC current ______a
e.g. Isc x 125% x # strings in parallel
PV output circuit to controller ______AWG
EGC size _______AWG
Charge Controller (CC) rating kW _____________
Controller DC circuit output ______AWG
OCD _____a
EGC size _______AWG
Battery Inverter name __________
rating kW_________
PV system rating DC ______kW
AC rating ______kW
Qty _____
□ UL1741
Battery type FLA, VRLA, Salt water, Li-ion, other ________________
Battery bank voltage ______v
capacity________kWh
Battery bank Isc ______
Battery bank disconnect label:
Nominal battery bank voltage ______
Max battery bank Isc _______
Arc clearing time for OCD ______
Date the calculation ______
65
DC disconnect label:
Max voltage ______v
Rapid shutdown:
Max current ______a
□ DC disconnect
□ Actuator
Max CC current _____a
□ N/A
Battery Inverter AC output ratings: (critical AC loads center)
AC disconnect label:
Operating voltage ______v
Operating current ______a
Battery Inverter AC input/output connection ratings: (interactive connection)
AC disconnect label:
Operating voltage ______v
Operating current ______a
 Backfed breaker connection in AC load center
Ampacities: Busbar _____a
Main OCD _____a
 Tap on load side of meter: Service feeders _____a
Inverter Imax x 125% _____a
Inverter OCD(s) _____a
66
Layout Diagram with Labels (Multimodal – DC coupled)
Place numbers by associated equipment location
Location list
1. Driveway at structure
2. Service meter
3. Main AC load center
4. PV array
5. Rapid shutdown device
6. PV array DC disconnect + label
7. Charge controller
8.
9.
10.
11.
12.
13.
Battery bank with disconnect + label
Battery inverter
Inverter AC output disconnect + label
Inverter AC input disconnect + label
Inverter interconnection point + label
Directory to all electrical power sources
67
Page 2e
 Multi-modal – AC coupled
Module name __________
rating _______watts
Max PV array DC voltage ______v
Qty _____
e.g. Voc x (1+(((C-(+25C)) x TCVoc)
 Controlled by inverter/PV optimizer
Max PV array DC current ______a
e.g. Isc x 125% x # strings in parallel
PV output circuit to inverter ______AWG
EGC size _______AWG
Interactive inverter name__________ rating kW_____
Qty _____
□ UL1741
Battery Inverter name __________
rating kW_________
Qty _____
□ UL1741
PV system rating DC ______kW
AC rating ______kW (battery inverter)
Battery type FLA, VRLA, Salt water, Li-ion, other ________________
Battery bank voltage ______v
capacity________kWh
Battery bank Isc ______
Battery bank disconnect label:
Nominal battery bank voltage ______
Max battery bank Isc _______
Arc clearing time for OCD ______
Date the calculation ______
68
DC disconnect label:
Max voltage ______v
Rapid shutdown:
Max current ______a
□ DC disconnect
□ Actuator
□ N/A
Interactive inverter ratings: (feeding into the critical AC loads center)
AC disconnect label:
Operating voltage ______v
Operating current ______a
Battery Inverter AC output ratings: (critical AC loads center)
AC disconnect label:
Operating voltage ______v
Operating current ______a
Battery Inverter AC input/output connection ratings: (interactive connection)
AC disconnect label:
Operating voltage ______v
Operating current ______a
 Backfed breaker connection in AC load center
Ampacities: Busbar _____a
Main OCD _____a
 Tap on load side of meter: Service feeders _____a
Inverter Imax x 125% _____a
Inverter OCD(s) _____a
69
Layout Diagram with Labels (Multimodal – AC coupled)
Place numbers by associated equipment location
Location list
1. Driveway at structure
2. Service meter
3. Main AC load center
4. PV array
5. Rapid shutdown device
6. PV array DC disconnect + label
7. Interactive inverter
8.
9.
10.
11.
12.
13.
14.
15.
Inverter AC disconnect + label
Rapid shutdown switch + label
Battery bank with disconnect + label
Battery inverter
Inverter AC output disconnect + label
Inverter AC input disconnect + label
Inverter interconnection point + label
Directory to all electrical power sources
70
Commercial Utility Interactive Inverters
Micro inverters: These attach to each module and convert the single module DC energy to
utility AC voltage (208v or 480v AC) (16v – 60v DC)
• One to four modules per inverter.
String inverters: A string inverter consists of a number of modules connected in series with 1
to 10 identical strings connected in parallel.
• Commercial string inverters are usually 12kW to 50kW rated (4 – 10 strings)
− (208v, 277v or 480v AC)
(200v – 1000v DC roof mounted)
Central inverters: A number of modules are connected in series with 20 to 300 strings
connected in parallel depending on the size of the inverter.
•
Central inverters consist of multiple combiner boxes feeding into a recombiner
located at the inverter location.
− 480v Ac
(200v – 1500v DC ground mounted)
Interactive with energy storage: Some residential models can be configured as 3-phase
commercial. There are also a few large scale high voltage energy storage inverters.
−
(208v – 480v AC)
(60v – 600v DC)
71
Commercial Flat Roof and Low Sloped
Ballast is typically used on flat roofs (27 lb concrete cap blocks).
• The weight of the blocks keeps the array in place during high wind conditions. Ballast
trays are connected to the module rack supports.
─ The roof must be rated to carry this excessive weight.
• This method accounts for the majority of flat roof installations.
Direct attachment is much less common because of higher installation cost.
• The array is usually 3’ to 4’ above the roof .
Direct attachment
Ballasted
72
Low Sloped Roof installations are direct mounted to the metal framing members
They are installed parallel to the roof in the same
manner as residential, or on a slightly tilted Aframe design.
• These are typical for small to medium-sized
manufacturing and service companies.
73
Ground mounted commercial systems are usually multi-pole.
The poles are usually pile driven or helical screwed into the ground.
• The poles are part of the grounding electrode system. If they are used as
electrodes they must be bonded to the exiting electrode system.
• Ground mounted systems perform better than roof mounted systems because of
cooler cell temperatures. They are also easier to service.
74
Parking Canopies
PV modules provide a dual purpose
function.
• The canopies provide sun protection
for cars or outdoor seating areas.
• Modules operate cooler and more
efficiently than roof mounts.
• Car canopies may also house battery
charging stations for electric cars.
75
Commercial Inverters and Locations
A rooftop PV system may use micro-inverters, string inverters or central inverters.
• The inverter AC and DC disconnects may be outside, inside, or on top of the building.
• The 2014 NEC requires Rapid shutdown within 10’ of the array; 1’ in 2017.
• Ground mounts may be 1500v and don not
require rapid shutdown devices.
Central inverter
String inverters
76
Commercial Voltage Considerations
AC power from the inverter shuts down with loss of power.
DC power is still present from the array to the inverter
• Micro-inverter systems will maintain low voltage at the module location.
 Safe to work on DC and AC side with AC power off
• String inverter systems vary depending on where the inverters are located.
− Roof located inverters contain high voltage very near the PV array.
 Safe to work on the AC side with AC power off
• String inverters systems with optimizers can reduce DC voltage with power outage
 Safe to work on DC and AC side with AC power off
• Central inverters were used on rooftop systems prior to 2013 but rarely after that.
 Be aware of the potential inside DC conduit when AC power is off
77
Permit information pertaining to the Commercial PV system
Check each that has been submitted
Page 1
 Ground mount drawings submitted
 Wind load data and calculations
 Erosion control plan
 Fence design and setback from PV array and equipment
 Roof mount drawings submitted
 Dead load and live load data and calculations
 Wind load data and calculations
 Grounding system submitted with electrical drawings
 Module grounding method
 Bonded railing components
 Fire Marshal submitted data
 Rapid shutdown method submitted with electrical drawings
 PV array setback with access and egress shown
78
Page 2
(do not fill in spaces on this sheet)
 Module, PV array and inverter data shown on electrical drawings
• Module data: Module name___, Pmax___, Voc___, Vmp___, Isc___, Imp___
• Array data: Max Power___, Number of modules in array___
Modules/string___, Max voltage (coldest day)___
Strings/combiner___, Max current (Isc x 125%)___
Combiners/inverter___, Max current (Isc x 125%)___
 Micro-inverter system data
• Inverter data: Inverter ID___, Power___, units/circuit___, circuit amps___, OCD___
• Output circuit
Number of circuits___, Total # of inverters___
Volts___, Conductor type___, Conductor AWG___, EGC___
Conduit type___, size___ length___
 String inverter system data
• Inverter data: Inverter name___, Rated power___, Volts___, current___
• Output circuit
Conductor type___, Conductor AWG___, EGC___, OCD___
Conduit type___, size___ length___
79
Page 2 continued (do not fill in spaces on this sheet)
 Central inverter system data
• Combiner output: Current (Isc x # of string x 125%)___, Max volts (coldest day)___
Conductor type___, Conductor AWG___, EGC___
Conduit type___, size___ length___
• Inverter input:
Current (Isc x # of strings x 125%)___, Max volts (coldest day)___
DC Overcurrent device___
(each)
• Inverter data:
Inverter name___, Rated power___, Volts___, current___
• Output circuit
Conductor type___, Conductor AWG___, EGC___. OCD___
Conduit type___, size___ length___
Grounding electrode system
 Ground mounted: Electrode system and GEC shown on electrical drawings
 Grounding electrode system data
 Grounding electrode conductor data
 Roof mounted: Equipment grounding conductor (EGC) bonded to AC grounding system.
80
Roof Layout
CAD quality drawings are required for commercial PV systems.
• In this example the four separate string inverter arrays are identified by color (atypical).
• The location of disconnects, rapid shutdown and conduit should be shown
81
The electrical riser diagram will be stamped by a Professional Engineer PE.
82
Labels and Placement
On all PV array DC output conduits attached to or ran
inside buildings
On the PV system disconnect:
• AC disconnect for interactive systems
• DC disconnect for DC coupled systems with
energy storage.
On all PV array output DC disconnects.
MAXIMUM CIRCUIT CURRENT
On all PV system inverter output AC disconnects.
On the switch that activates the rapid shutdown device.
• AC disconnect for most interactive systems
• DC disconnect or UL listed device on DC coupled
systems with energy storage.
83
Labels and Placement
Within 3 feet of the service disconnect. This addresses
PV output circuits outside the PV array 1 foot boundary.
The 2014 array boundary is 10 feet outside/5 feet inside.
• The placard must also denote the location of the
rapid shutdown switch if it is not within sight of the
service location.
Effective January 1st 2019
Within 3 feet of the service disconnect. This addresses
PV output circuits outside the PV array 1 foot boundary.
It also addresses the voltage inside the array boundary.
• This is the part that will be effective on 1/1/2019
84
Labels and Placement
MULTIPLE POWER SOURCES
X
PV array
DC disconnect
Article 706.11
Installed at the service equipment location.
PV system
AC disconnect
X
Utility service
AC disconnect
X
• The only guideline to this plaque or directory is that
is comply with Article 110.21(B) for letter height and
durability
• This may be a written directory or a drawing with
writing as shown in this example.
Installed at a location acceptable to the authority
having jurisdiction (AHJ).
• Off-grid stand-alone system. The plaque should be
as you approach the structure from the driveway.
• Utility connect stand-alone system. The plaque
should be at the service location.
85
Labels and Placement
Placed next to the inverter breaker back-feeding a
branch circuit AC load center.
Placed on disconnects where the terminals are readily
accessible and live when the disconnect is off and open.
• The bottom terminals are load side and usually deenergized when the disconnect is off.
− PV systems often backfeed circuits.
On equipment other than in dwelling units where the
circuits can be accessed when energized.
• Most string inverters have dead front access panels to
reduce this hazard.
• This usually occurs at AC switchgear.
86
Important components of permitting
Line diagram: Shows the flow of energy and makes it easier for the inspector to see what
each part of the system is doing.
• Numerically referenced details on the line diagram. This provides a 1-2-3 process of
installation verification for inspectors so that field calculations are unnecessary.
Layout diagram: Shows the location of all parts of the system, disconnects and directories.
List of labels: The label provides easy visual inspection.
• Contractors who provide accurate labels at all required locations are more likely to
have a code compliant installation than those who don’t.
Cost of permit: It is important for a contractor to know the cost of permitting
Example:
Base cost for residential interactive
Base cost for residential with energy storage
Adder:
$/kW AC
Who can pull a permit: The State of Georgia requires a contractor to be licensed contractor.
• PV Systems fall under General contractor or electrical contractor.
• Electrical contractor must attach an affidavit if a general contractor pulls the permit.
87
Question and Answer wrap up
SOLAIRGEN
School of Solar technology
www.solairgen.com
119 Highway 52 West
Dahlonega, GA 30533
706-867-0678
info@solairgen.com
88
89
Permitting and Inspecting PV Systems
PV 403
Part 2
Inspecting Solar Electric (PV) Systems
Created and Written by: Kelly Provence
90
Key Code Issues with PV Systems
Physical installation:
• Access on the roof for first responders and service personnel
• Loading on the roof: Dead load limits and wind lift forces
• Attachments and penetrations affecting the roof integrity
Electrical installation (PV systems and the NEC)
• Improper grounding
• Poorly made connections or non-code compliant connector use
• Overvoltage on equipment or connectors
• Inadequate conductor size and protection
• Incorrect disconnect installation and placement
• Missing or inadequate labeling
• Non-compliant AC connection to service equipment.
91
Access to the Roof
Residential PV Array Pitched Roof Access
The modules are installed parallel to the roof so energy density is maximized.
• There should be roof access for other contractors and first responders.
• 3’ to the sides and top should be minimum for access.
 Most installations follow these guidelines but not all.
92
Three foot minimum access is recommended
93
Commercial PV Array Low Sloped Roof Access
Modules are installed in tilted rows that provide 18” to 24” between each row. This is not
service access.
• Aisle-ways should be minimum 4’, clearance to edge of roof should be minimum 6’
150’
4’
150’
6’
6’
8’ walkway
 Most installations provide more access than this guideline .
94
Physical Installation
Dead Loads. The weight of materials of construction incorporated into the building,
including but not limited to walls, floors, roofs, ceilings, stairways, built-in partitions,
finishes, cladding and other similarly incorporated architectural and structural items,
and the weight of fixed service equipment, such as cranes, plumbing stacks and risers,
electrical feeders, heating, ventilating and air-conditioning systems, automatic sprinkler
systems and solar installations.
•
PV array directly attached parallel to roof; less than 4lb/ft²
Live Loads. Those loads produced (1) during maintenance by workers, equipment and
materials; and (2) during the life of the structure by movable objects such as planters
and by people.
Environmental loads. Wind load, snow load, rain load, earthquake load, flood load
Nominal Loads. The magnitudes of the loads (dead, live, soil, wind, snow, rain, flood
and earthquake).
95
Dead Loads and Live Loads on Roofs
Residential roof dead load on the rafters are as following:
•
Totals
½” Roof decking, plywood or OSB
1.5 lb.ft²
− Asphalt or wood shingle, metal sheet roofing
2 lb/ft²
3.5 lb/ft²
− Conventional clay/tile roofing
15 lb/ft²
16.5 lb/ft²
Commercial membrane roofs with metal decking and insulation
5 lb/ft²
Standard dead load ratings for residential and commercial roofs.
10 lb to 20 lb/ft²
•
Consult the American wood council rafter span charts for details
•
Consult the International Building Code (IBC )and the American Society of Civil
Engineers (ASCE) 5-7 for snow and wind loads.
Live loads for most flat and sloped building roofs.
UNIFORM
CONCENTRATED
20 lb/ft²
300 lb/ft²
 Commercial roofs may have very little dead load margin for ballasted PV systems. A
Structural or Professional Engineer (PE) will need to make the load assessment.
96
Weight Loads and Wind Lift Loads
Static loads are the weight of the PV array and ballasting to resist against wind lift.
Roof mounted PV arrays
Total
• PV module weight
2.5 lb to 3 lb per ft².
3 lb/ft²
• Residential flush mounted racking
.25 lb to .5 lb per ft².
3.5 lb/ft²
− Residential roofs are sufficient unless under built to begin with.
• Commercial flat roof racking without ballast
1 lb per ft².
4 lb/ft²
― Concrete blocks used for ballast weigh 27 lb
Flat roof mounted arrays occupy ≈ 28ft² per module
6 blocks x 27 lb = 162 lb ÷ 28ft² =
5.8 lb/ft² + 4 lb.ft² =
9.8 lb/ft²
Commercial roofs may require an engineer's calculation.
Ground mounts
― Pole mounted arrays will add about 4 lb to 5 lb per ft² without concrete.
― Poured concrete weighs around 100 lb to 130 lb per ft³.
― Penetrated ground resistance depend on soil type.
97
Ground Snow Loads for the
Southeastern United States.
Taken from 2009 IBC
98
• Wind speeds are based on a 3 second gust at 33 feet (10 meters) above ground.
90 (40)
99
Wind exposure areas of the roof
100
ASCE 7-05; Chapter 6 Wind Loads
Structural Compliance:
Racking companies provide pre-engineered components and installation instructions.
• Require the contractor/installer to provide the racking design specifications (white paper).
Total of attachments for the PV array must equal the total wind lift lb/ft².
• Residential racking systems are pre-engineered for at least 90mph
• Commercial racking system will provide engineering data for each customer design.
101
Attachment on Steep Sloped Roofs
Lag screws are the most common type of fastener
used to attach array mounting systems to wood
structures, usually residential roofs.
•
Calculate withdrawal strength
•
Pre-drill hole 2/3 screw diameter
•
Use butyl caulk and flashing
PV arrays flashed mount standoffs and attachment
All steep sloped roofs required an attachment and module mount system.
102
Direct Attachment
Asphalt shingle roofs can be sealed with direct attachment
Butyl tape allows for the rail-less direct attachment.
•
The butyl tape is placed below the attachment and
Self-seals when neoprene washer screws are used
to attach to the roof.
Roof Tech
103
Metal roofs are either corrugated or
standing seam.
1. The most secure attachment must be sealed by a
roofer
2. This is very secure if the bolt penetrates a rafter.
It is less secure if it secures only to the lap seam.
3. This attachment is secured only to the metal roof
but make no penetration and is leak-proof.
1. Attached structural rafters
2. Attached to the corrugated lap seam
3. Attached to the standing seam
104
Most common violations
Residential:
1. Bolting and flashing to the roof are the two areas where installers make mistakes with the
physical installation.
• Selecting the wrong grade of lag bolt. (residential systems use stainless steel)
• Galvanic corrosion: Stainless steel and tinned copper are used to prevent corrosion.
• Improper torqueing of the bolts
• Missing the rafter with the lag bolt or splitting the rafter.
• Direct attachment without flashing: The potential to improperly install sealant.
2. Insufficient setback from vent pipes and other roof structures.
Addressing these potential violations:
1. Since these are almost impossible to see these areas with roof mounts, it may be beneficial
to have the contractor list the materials and methods of attachment (on the permit).
2. It is easy to see setbacks from the ground.
− Cut off vent pipes may be difficult to see without a high powered flashlight or a visit
into the attic to see if there are vent pipes located where the PV array is located.
105
Most common violations
Commercial:
1. Improper installation of ballasted array have the greatest potential for roof damage.
• Exceeding the roof structure dead load rating.
• Failure to distribute the ballast as the roofing manufacture has specified for wind lift.
• Failure to protect the roof membrane from sharp edges of metal or plastic racking.
• Setting ballast treys directly on top of roofing rock ballast (membrane scaring).
2. Insufficient setbacks and clearances for walkways
Addressing these potential violations:
1. Require an engineer's letter of dead and live load for the roof.
− Require a copy of the engineered layout for the PV array and ballast load distribution.
− Require the contractor to show the method of membrane protection on the permit.
− It will be obvious if the PV array is sitting on the roof ballast or membrane.
2. It will be easy to see if necessary setbacks have be observed for other equipment.
− 48” minimum from electrical equipment, 42” minimum from metallic structures
− 48” minimum for walkways
106
PV Systems and the NEC
The text is taken directly from the 2014 and 2017 NEC with minor rephrasing.
− Rephrasing in this course is not to be considered official substitution for NEC text.
2017 NEC additions or changes are highlighted blue or with a blue bar to the left.
2014 NEC text deleted from 2017 NEC are highlighted in purple.
Comments are usually indicated by the use of this symbol:
before the
comment, e.g.
 Author’s comments
Authorities having jurisdiction (AHJs) usually adopt the latest NEC version one
year after it’s official date. Persons engaging in electrical work should possess
three NEC versions; previous, current and upcoming when made available.
 Many changes to solar PV articles in the 2017 NEC are clarifications. These should
be implemented immediately.
 Some other changes are already in place as a common practice but will not become
law until Georgia adopts the 2017 version.
107
PV System Safety Compliance Requirements
• Residential DC Voltage is limited to 600v. PV voltage rises with cold temperatures so this
must be calculated using ASHRAE minimum mean temperature.
• Commercial DC Voltage is limited to 1000v. PV voltage rises with cold temperatures so
this must be calculated using ASHRAE minimum mean temperature.
• Rapid shutdown for first responders. Rooftop PV arrays must reduce voltage 1’ outside
the array boundary to 30v in 10 seconds when the rapid shutdown device is activated.
− Micro-inverters and SolarEdge control this; others require the installer to install it.
• Anti-islanding UL1741 listed inverters. The inverter must stop sending power into the
grid during an outage.
− Included in all UL 1741 listed inverters
• GFDI equipped. The system must have ground fault detection on the PV array DC circuit
that detects ground faults and shuts down equipment connected to the array if detected.
− Included in all interactive inverters; installer provides this with battery systems.
• AFCI equipped. The system must have arc-fault detection on the PV array DC circuit that
detect arcs from the array and shuts down equipment connected to the array if detected.
− Included in all interactive inverters; installer provides this with battery systems.
108
Significant changes from 2014 to 2017 NEC
• 1500vdc is allowed with ground mounted PV arrays. New
• Articles referencing voltage above 1000v have further replaced the previous references
to above 600v. New
• Rapid shutdown requirements have been expanded and clarified; the boundary is now
restricted to one foot of the PV array. New and redefined
• Fusing both + and – is no longer required with ungrounded systems so long as there is a
disconnect that opens both conductors simultaneously. New clarification
• PV wire requirement for ungrounded systems is rewritten to allow USE-2 if AC side has
a grounded neutral. New clarification
• Grounded PV array conductors do not require the white marking if GFDI is the bonding
point to the ground (functionally grounded). New clarification
• Grounding electrode conductor requirements are simplified. Reduced and clarified
• Article 691 Large Scale PV Systems was added for systems sized 5MW and larger. New
• Article 706 Energy Storage Systems and Article 710 Stand-Alone Systems were added
and Articles were moved from Article 690. Moved, clarified and expanded
109
Important NEC Terms
Accessible (as applied to wiring methods): Capable of being removed or exposed without
damaging the building structure or finish or not permanently closed in by the structure
or finish of the building.
Accessible, Readily (Readily Accessible): Capable of being reached quickly for operation,
renewal, or inspections without requiring those to whom ready access is required to
use tools (other than keys), to climb over or remove obstacles or to resort to portable
ladders, and so forth.
Functional Grounded PV System. A PV system that has an electrical reference to ground
that is not solidly grounded.
 This is a new term for defining grounded PV arrays with a GFDI device.
− The 1a to 4a GFDI fuse does not provide a solidly grounded conductor
− A solidly grounded PV system would not have a GFDI fuse or a GFDI device.
− In the U.S. most AC services are solidly grounded at the main AC disconnect. It
is extremely rare for a PV system to be solidly grounded.
Voltage, Nominal: A value assigned to a circuit or system for the purpose of conveniently
designating its voltage class (e.g., 120/240 volts, 480Y/277 volts, 600 volts).
Informational Note # 3: Battery units rated at nominal 48 volts DC may have a charging voltage
up to 58 volts. In DC applications, 60 volts is used to cover the entire range of float voltages.
110
Other NEC Terms for PV Systems
Alternating-Current (AC) Module: A complete, environmentally protected unit
consisting of solar cells, optics, inverter, and other components, exclusive of tracker,
designed to generate AC power when exposed to sunlight.
Charge Controller: Equipment that controls DC voltage or DC current, or both, used to
charge a battery.
Diversion Charge Controller: Equipment that regulates the charging process of a battery
by diverting power from energy storage to direct-current or alternating-current loads
or to an interconnected utility service.
DC to DC Converter: A device installed in the PV source or output circuit that can
provide an output DC voltage and current at a higher or lower value than the input
DC voltage or current. (MPPT devices) (PV Optimizers)
DC-to-DC Converter Output Circuit. Circuit conductors between the dc-to-dc converter
source circuit(s) and the inverter or dc utilization equipment.
DC-to-DC Converter Source Circuit. Circuits between dc-to-dc converters and from dcto-dc converters to the common connection point(s) of the dc system.
111
Generating Capacity. The sum of parallel-connected inverter maximum continuous output
power at 40°C in kilowatts.
Hybrid System: A system comprised of multiple power sources. These power sources may
include photovoltaic, wind, micro-hydro generators, engine-driven generators, etc...
Interactive System: A solar PV system that operates in parallel with and may deliver power
to an electrical production and distribution network. For this definition an energy
storage subsystem of a solar PV system, is not another electrical production source.
Multimodal (formerly Bimodal): Equipment having the capabilities of both utilityinteractive inverter and stand-alone inverter.
Stand-Alone System: A solar photovoltaic system that supplies power independently of an
electrical production and distribution network.

Battery storage systems are typical with stand-alone, however a solar well pump
that operates without battery storage is also a stand alone system.
112
PV System Grounding
690.41 System Grounding.
(A) PV System Grounding Configurations. One or more of the following system grounding
configurations shall be employed:
(1) 2-wire PV arrays with one functional grounded conductor

GFDI fuse connecting the grounding conductor and a current conductor.
(2) Bipolar PV arrays according to 690.7(C) with a functional center ground reference.
(3) PV arrays not isolated from the grounded inverter output circuit
(4) Ungrounded PV arrays

The reference to article 690.35 was removed along with 690.35.
Both (3) and (4) regard the AC side grounded conductor to be adequate.
(5) Solidly grounded PV arrays as permitted in 690.41(B)Exception

See next slide for Exception.
(6) PV systems that use other methods that accomplish equivalent system protection in
accordance with 250.4(A) with equipment listed and identified for the use.
 At least 99.9% of the systems installed in the U.S. will fall under (1) or (4)
• Most are ungrounded PV arrays.
113
690.41 System Grounding.
 This 2017 NEC article below was moved from 690.5 of 2014.
(B) Ground-Fault Protection. DC PV arrays shall be provided with dc ground-fault protection
meeting the requirements of 690.41(B)(1) and (2) to reduce fire hazards.
Exception: PV arrays with not more than two PV source circuits and with all PV system
dc circuits not on or in buildings shall be permitted without ground-fault protection
where solidly grounded.
(1) Ground-Fault Detection. The ground fault protective device or system shall detect
ground fault(s) in the PV array DC conductors and components or any functional
grounded conductors; it must be listed for providing PV ground-fault protection.
(2) Isolating Faulted Circuits. The faulted circuits shall be isolated by one of the
following methods:
(1) The current-carrying conductors of the faulted circuit shall be automatically
disconnected.
(2) The inverter or charge controller fed by the faulted circuit shall automatically
cease to supply power to output circuits and isolate the PV system dc circuits
from the ground reference in a functional grounded system.
 Both grounded and ungrounded systems are included in the article. The special
requirements for ungrounded systems has be removed because it was illogical.
114
Location of GFDI
Interactive systems:
Grounded inverters have a fuse built
into the inverter. It is protected but
accessible by screw attachment.
Ungrounded inverters use an internal
high impedance reference connection
(+ to G) and (- to G).
Battery based systems: Grounded
+
G
+
Charge controllers may have a fuse built into it. If so, it is
protected but accessible by screw attachment.
DC load centers are a common location for this device. The breaker
will be in tandem with one or two PV array inputs.
 Residential grounded systems: Fuses are .5 to 1 amp
 Commercial grounded systems: Fuses are 2 to 5 amp
 Ungrounded systems: Shut down at .3 amps
+
-
+
115
Equipment grounding and bonding requirements
690.43 Equipment Grounding. Exposed non–current-carrying metal parts of module frames,
equipment, and conductor enclosures shall be grounded in accordance with Art. 250.134 or
250.136(A) regardless of voltage.
(A) PV Module Mounting Systems and Devices. Devices and systems used for mounting PV
modules and for bonding module frames shall be listed, labeled, and identified for bonding
PV modules. Devices that mount adjacent PV modules shall be permitted to bond them.
(B) Equipment Secured to Grounded Metal Supports. Devices listed, labeled, and identified for
bonding and grounding the metal parts of PV systems shall be permitted to bond the
equipment to grounded metal supports. Grounding shall be contiguous from rail to rail
section by use of a listed bonding jumper.
Rail to rail
Rail to grounding conductor
Module to rail
(C) With Circuit Conductors. Equipment grounding conductors shall be ran with array
conductors within and beyond the array.
 Module frames and metal racking provide grounding within the array boundary.
116
Integrated bonding is now standard with most raking systems
#6 copper provides EGC bond to all rails
Tinned coper bonding lug
#14 - #4 CU
Bonds to module
Bonds to module
Bonds to rail
End clamp
Bonds to rail
Mid clamp
117
Size of Equipment Grounding Conductors
690.45 Size of Equipment Grounding Conductors. Equipment grounding conductors for PV
source and PV output circuits shall be sized in accordance with 250.122.
Where no overcurrent protective device is used in the circuit, an assumed overcurrent
device rated in accordance with 690.9(B) shall be used.
e.g. PV max circuit current = Isc x 125% x 125% = OCD
•
Increases in equipment grounding conductor size to address voltage drop
considerations shall not be required.
•
The equipment grounding conductors shall be no smaller than 14 AWG.
690.46 Array Equipment Grounding Conductors
The article states that EGC smaller than #6 shall comply with 250.120(C)
• Where installed in a raceway, PV array EGCs and GECs not larger than #6 AWG shall be
permitted to be solid.
250.120 (C) Equipment grounding conductors smaller than 6 AWG shall be protected from
physical damage.
 The smallest equipment grounding conductor not ran in a conduit is #6 cu.
118
Table 250.122 Size of Equipment Grounding Conductors (EGC)
 Size all grounding conductors using the chart below.
 Always use copper conductors for exterior applications.
119
Bonding Requirements
250.98 Bonding Loosely Jointed Metal Raceways. Expansion fittings and telescoping
sections of metal raceways shall be made electrically continuous by bonding jumpers.
 Railing is commonly jointed to other sections for larger PV array rows.
• Newer bond rated splices are now being provided by the racking companies.
• If the splice is not bond rated, a bonding jumper must be installed.
Expansion joint bond
120
Review: Equipment Grounding Requirements
 A functionally grounded system is not solidly grounded. The functional ground is either a
GFDI fuse or low amperage or a high impedance electrical reference.
 Solidly grounded PV systems only occur on small ground mounted arrays with two or less strings and
no DC components connected to a building.
 AC electrical systems are almost always solidly grounded with the neutral and grounding conductor
boned at the service disconnect location.
 Ground fault detection is required on all PV array source and output circuit conductus that are not
solidly grounded.
 Exposed non-current carrying metallic part of PV system and other electrical equipment must be
grounded and connected to the premises grounding system.
 Equipment grounding conductors are sized in Table 250.122. The assumed OCD used in the table is
calculated from the continuous current x 125%.
 When current carrying conductors are oversized to compensate for voltage drop, equipment conductors
are not required to be size up proportionally.
 Equipment grounding conductors smaller than #6 must be protected from physical damage.
 Insulated grounding conductors must be colored solid green or green and yellow. Conductors sized #4
and larger may be marked with green tape at their point of access.
 PV array bonding devices must be listed for the environment and use.
121
Review: Equipment Grounding Requirements, cont.
 Conduits used a grounding path must be bonded together with listed conduit connectors.
 Bonding jumpers are required where metal parts of normally grounded systems are not
solidly bonded.
 The 2017 NEC removes the requirement to mark a functionally grounded PV source or
output conductor white. Only solidly grounded conductors are to be marked white.
 AC side neutral conductors are to be marked white or light grey.
122
Most common violations
1. Exposed PV array EGC is sized smaller than #6.
2. Bonding connectors are not properly torqued.
3. Bonding lugs between rails are not listed for the use and environment.
4. DC coupled battery based systems fail to install a GFDI device.
Addressing these potential violations.
1. Ground mounts are easy to see. Roof mounts are not easy to see; ask for verification on
exposed EGC during the inspection (#6 minimum).
2. PV modules, racking systems and inverters all provide instructions on torque spec. Ask
for a sheet on torque specs and ask how it was verified.
3. I have seen aluminum grounding lugs used on PV arrays . They should be tinned copper
or stainless steel. Ask for verification on the grounding lugs.
− Micro-inverters use integrated bonding so issues in #1 and #3 are addressed by the
manufacture. Violating the installation procedures would violate the warranty.
4. Look for the GFDI device in either the charge controller or the DC panel.
123
Grounding Electrode System Requirements for PV Systems
690.47 Grounding Electrode System.
(A) Buildings or Structures Supporting a PV Array. A building or structure supporting a PV
array shall have a grounding electrode system installed in accordance with Part III of
Article 250.

This is the same requirement for AC grounding electrodes outlined on
subsequent slides.
PV array equipment grounding conductors shall be connected to the grounding
electrode system of the building or structure supporting the PV array in accordance with
Part VII of Article 250.
Part VII 250.130(A) For Grounded Systems. The connection shall be made by bonding
the equipment grounding conductor to the grounded service conductor and the
grounding electrode conductor.

This refers to the AC grounded system. In the U.S. the gross majority of AC
electrical system are grounded.

This connection will usually be made by bonding the DC equipment grounding
conductor to the AC equipment grounding at the inverter.
124
Grounding Electrode System Requirements for PV Systems
(A) Continued. For PV systems that are not solidly grounded, the equipment grounding
conductor for the output of the PV system, connected to associated distribution
equipment, shall be permitted to be the connection to ground for ground-fault protection
and equipment grounding of the PV array.

In other words, the bond between the PV array equipment ground may be
bonded to the inverter AC equipment bond. This is the necessary bond to the AC
grounding electrode system.
For solidly grounded PV systems, as permitted in 690.41(A) (5), the grounded
conductor shall be connected to a grounding electrode system by means of a grounding
electrode conductor sized in accordance with 250.166.

These are the small isolated PV arrays with not more than two PV source
circuits not on or in buildings.

Review the requirement for 250.166 on subsequent slides
Informational Note: Most PV systems installed in the past decade are actually functional grounded
systems rather than solidly grounded systems as defined in this Code. For functional grounded PV
systems with an interactive inverter output, the ac equipment grounding conductor is connected to
associated grounded ac distribution equipment. This connection is often the connection to ground
for ground-fault protection and equipment grounding of the PV array.

The bond is in the inverter and/or the location of GFDI.
125
690.47(B ) Additional Auxiliary Electrodes for Array Grounding.
Grounding electrodes shall be permitted to be installed in accordance with 250.52 and
250.54 at the location of ground and roof-mounted PV arrays.
• The electrodes are permitted to be connected directly to the array frame(s) or structure.
• The grounding electrode conductor shall be sized according to 250.66.
• The structure of a ground-mounted PV array shall be permitted to be considered a
grounding electrode if it meets the requirements of 250.52.
• Roof mounted PV arrays shall be permitted to use the metal frame of a building or
structure if the requirements of 250.52(A)(2) are met.

Auxiliary grounding electrodes by definition are not bonded to the existing
grounding electrode system and are not required to comply with 25Ω to ground.

This electrode should either be bonded to the existing electrode system or it should
have a resistance to ground of 25Ω or less, otherwise it should not be installed.
NOTE: The primary reason for an auxiliary grounding electrode is to protect against
lighting strikes. Failure to tie it into the existing electrode system will increase
exposure to ground lighting dispersal effects.
126
Roof Mounted PV Array
Functionally grounded Systems with GFDI:
 The array equipment grounding conductor is bonded to the inverter AC EGC.
Roof mounted
PV array
Bonding point EGC and GEC
127
Roof Mounted PV Array
Functionally grounded Systems with GFDI:
 The auxiliary grounding electrode (if used) should be bonded to the premises GEC.
Only for lightning prone areas
Roof mounted
PV array
Axillary GEC bonded to EGC and premises GEC
128
Ground Mounted PV Array
Functionally grounded Systems with GFDI:
 The GEC from the PV array to the premises grounding electrode system must be no
smaller than the existing GEC.
Ground mounted PV array
Frame of the PV array connected
to existing electrode system
129
Ground Mounted PV Array
Functionally grounded Systems with GFDI:
 The PV array grounding electrode must be installed according to 250 Part III.
Ground mounted PV array
Frame of the PV array must meet
grounding electrode requirements
130
Approved Grounding Electrodes
250.52 Grounding Electrodes; specifies the approved methods and materials to effectively
ground AC and DC systems.
(A) Electrodes Permitted for Grounding.
(1) Metal underground water pipes (10 feet underground)
(2) Metal In-ground Support Structure(s) with or without concrete (10 feet vertically
contacting the earth).
• If multiple of these support structures are present at a building or a structure, it
shall be permissible to bond only one into the grounding electrode system.
(3) Concrete encased electrode (20’ #4 cu or corrosion resistant ½ inch metal bar)
(4) Grounding ring (20 feet of #2 AWG cu 30 inches below surface of earth)
(5) Rod electrode (8 feet in length 5/8’ diameter 30 inches below SOE)
(6) Other listed electrodes
(7) Plate electrodes (2 ft² surface ¼ inch diameter and 30 inches below SOE)
(8) Other local metal underground structures
 Grounding electrode systems must provide a low resistance to earth ground. The NEC
specifies 25 ohms or less as the minimum standard.
• The system owner or engineer may specify a lower resistance.
131
Review: Grounding Electrode Requirements
 A DC grounding electrode system is required for buildings or structures supporting a PV
array.
• Where an AC system is installed on the structure with a grounding electrode system,
this will be the grounding electrode system for the PV array.
• Where a PV array is installed on the ground, a grounding electrode system must be
installed in accordance with Article 250 Part III.
• Additional auxiliary grounding electrodes for array grounding are permitted to be
installed at or as close to the PV array location as possible. They must meet the
standard for grounding electrodes set forth in article 250.52.
− If installed, they should be bonded to the existing grounding electrode system.
 DC Grounding electrode conductors are only required where a PV array is ground mounted
or an auxiliary grounding electrode system has been installed.
• DC grounding electrode conductors are required to connect system grounding
conductors with the grounding electrode systems.
 AC Grounding electrode conductors are required at the first point of disconnect where
equipment grounding conductors and solidly grounded conductors are bonded.
• On the AC side this is at the service disconnect.
132
Most common violations
Ground mounted systems:
1. Inadequate DC grounding electrode system.
2. Failure to protect the grounding electrode conductor
Addressing these potential violations.
1. Inadequate DC grounding electrode system for ground mounted systems
• A separate auxiliary ground in electrode system should be connected to the existing AC
grounding electrode system with a bonding conductor sized to the larger of the two.
• If the existing grounding electrode system is further than 100’ from the PV array, the
DC grounding electrode system must meet Article 250.52 requirements.
2. Failure to protect the grounding electrode conductor.
• A #6 copper GEC requires no additional protection as long as it is attached to a
building or the electrical equipment structure.
− A #4 is required when the GEC is ran to the grounding electrode system away from
protection unless it is in conduit or ran underground. e.g. 18”
133
Voltage Limits and Calculations
Art. 690.7 Maximum Voltage
The maximum voltage of PV system dc circuits shall be the highest voltage between any two
circuit conductors or any conductor and ground.
• PV system dc circuits on or in one- and two-family dwellings shall be permitted to have a
maximum voltage of 600 volts or less.
• PV system dc circuits on or in other types of buildings shall be permitted to have a
maximum voltage of 1000 volts or less.
• Where not located on or in buildings, listed dc PV equipment, rated at a maximum voltage
of 1500 volts or less, shall not be required to comply with Parts II and III of Article 490.
Art. 490 Part II Equipment (Switchgear and Industrial Control Assemblies) covers
overcurrent device ratings and locations.
Art. 490 Part III EQPT. (Specific Provisions) covers disconnect locations and ratings.
Table 490.24 provides minimum clearances for live parts.
 The 1500v provision is for commercial ground mounted PV arrays. All
equipment used for installation and testing must be rated 1500v.
134
Voltage Calculations
Art. 690.7(A) Photovoltaic Source and Output Circuits Use one of the following.
(1) Use the PV module manufactures Standard Test Conditions STC temperature
coefficients (TCVoc) and module Voc. Calculate the coldest day voltage from the
module data and number of modules in series.
e.g. Voc x (1+(TCVoc x temperature difference from STC))
(2) Multiply Table 690.7 temperature correction factor times the module STC Voc and
number of modules in series. (for c-Si modules without temperature coefficients)
(3) PV systems of 100kW or larger may use an alternate industry standard method
calculated by a licensed professional electrical engineer.

This includes 5MW plus PV systems noted in 691.6 and 691.8.
Art. 690.7(B) DC-to-DC Converter Source and Output Circuits
(1) Single DC-to-DC Converter. The max voltage for output circuits of the dc-to-dc
converter shall be the maximum rated voltage output of the dc-to-dc converter.
(2) Series Connected DC-to-DC Converters. Go by manufactures instructions.
•
If not stated in the instructions the max voltage shall be the sum of the max
ratings of the DC-to-DC converters connected in series
135
(A)(1) Method Example
The NEC suggests using the ASHRAE table for a minimum temperatures source.
Excerpt from ASHRAE table
Temperature difference between the extreme annual min. temp and STC 25°C
e.g. Module data sheet STC Voc of 36v and TCVoc of .35%/°C
Atlanta ASHRAE minimum temperature is -12°C 37°C lower than STC 25°C
36v x (1+(37°C x .0035)) = 40.662v max voltage for the module
(1.1295) use 1.13 as a generic standard for Atlanta
14 module in series x 40.662v = 569v max system voltage

Residential interactive string inverters usually have a 600v max, 12 to 14 in series.
Micro-inverters often have a max voltage of 48v, 1 module per inverter
136
(B)(1) and (2) Example
DC-to-DC converter
48
8 - 48
59.3-60-60.5
15
60
500
350
The inverter and DC to DC converter limit string voltage to 500v
137
Review: Voltage Limits and Requirements
 Residential voltage max is 600v
 Commercial rooftop voltage max is 1000v
 Commercial ground mount voltage max is 1500v
 Max PV array voltage = Voc x (1+(coldest day temp. difference from STC x TCVoc))
• PV inverter/optimizer controlled max voltage is provided by the manufacturer.
 Maximum DC-DC (optimizer) voltage is listed on the device or system
Most common violations
Voltage violations with interactive PV systems are almost unheard of because design programs
are readily available from inverter manufacturers.
• The inverter and other electronic equipment also monitor voltage.
Addressing this potential violation.
Rule-of-thumb formula for Atlanta, GA: Find the PV module Voc and use the following.
Voc x number of modules in series x 1.13 = Max voltage on coldest day
NOTE: SolarEdge controls voltage; this should be shown on the permit.
138
Conductor Properties and selection
• USE-2 or PV wire is used for PV array source conductors.
• THWN-2 or XHHW-2 is used in conduit ran outside and/or underground
• THHN is used in conduit ran indoors
139
Conditions of Use
310.10 Uses Permitted: Conductors are exposed to several climatic conditions and they
must be rated for these conditions.
• Some of these are dry, moist, wet, direct burial, low and high temperatures, UV light
exposure, hard use, corrosive material and proximity to other conductors or equipment.
• The conductors must be rated or listed for the specific condition of use.
(A) Dry locations: all conductors listed in the NEC are rated for dry locations
(B) Dry and Damp locations: The following types are rated for damp locations. FEP,
FEPB, MTW, PFA, RHH, RHW, RHW-2, SA, THHN, THW, THW-2, THHW,
THWN, THWN-2, TW, XHH, XHHW, XHHW-2, Z, or ZW.
(C) Wet locations: MTW, RHW, RHW-2, TW, THW, THW-2, THHW, THWN, THWN2, XHHW, XHHW-2, or ZW or be listed for use in wet locations
 Conductors ran in conduit underground are in a Wet Location.
 It is best to check the conductor manufactures listing for specifics. Many
conductors have multiple listings for type and use.
140
Conductor Bending Radius
Each conductor has a maximum bending radius depending on the type, specs and voltage.
• The radius is given in # times the diameter of the conductor.
e.g. Chapter 9 Table 5 provides diameters for several cable types.
#10 RHW-2 = .236” diameter x radius factor of 8 = 1.89” bending radius
1.89 x 3.16 = 5.93”
USE-2 is allowed a maximum radius
of 5x the diameter in Art. 338.24.
e.g. 5 x .236 = 1.18”
< 1.89” >
< 1.89” >
5.93”
About the radius of a coffee cup
141
Determine Circuit Continuous Rating
690.8 (A) Calculation of Maximum Circuit Current.
(1) PV source Circuit Current
(1) The sum of parallel-connected PV module–rated short circuit currents (Isc) x 125%.
 # of modules connected in series x Isc x 125% = max continuous current
(2) For PV systems with a generating capacity of 100 kW or greater, a documented and
stamped PV system design, using an industry standard method and provided by a
licensed professional electrical engineer, shall be permitted.
•
The current value shall be based on the highest 3-hour current average resulting
from the simulated local irradiance on the PV array accounting for elevation and
orientation.
•
The current value used by this method shall not be less than 70 percent of the value
calculated using 690.8(A)(1)(1).

The National Solar Irradiation Database can be used with the program
behind PVWATTS to determine 3-hour irradiation measurements for
various tilts and azimuths at a great number of locations.
142
690.8 (A) Calculation of Maximum Circuit Current.
(2) Photovoltaic Output Circuit Currents. The maximum current shall be the sum of
parallel source circuit maximum currents as calculated in 690.8(A)(1).
(3) Inverter Output Circuit Current. The listed maximum current shall be the inverter
continuous output current rating.
(5) DC to DC Converter Output Current. The maximum current shall be the dc- to-dc
converter continuous output rating..
Determine Circuit Ampacity Requirements
690.8 (B) Conductor Ampacity. PV system currents shall be considered to be continuous.
Circuit conductors shall be sized to carry not less than the larger of 690.8(B)(1) or (2).
Or where protected by a listed adjustable electronic overcurrent protective device in
accordance 690.9(B)(3), not less than its current rating.
(1) One hundred and twenty-five percent (125%) of the maximum currents calculated
in 690.8(A) before the application of adjustment and correction factors.
e.g. Circuit continuous current x 125% = required conductor ampacity.
143
Equipment Lug Temperature Limitations
Art. 110.14 Electrical Connections
(C) Temperature Limitations; The temperature rating associated with the ampacity of a
conductor shall be selected and coordinated so as not to exceed the lowest temperature
rating of any connected termination, conductor, or device.

Equipment is sometimes rated lower than the selected conductor.
Some AC
equipment
Some residential
DC equipment
Most commercial
DC equipment
144
Ampacity Rating of Conductors
310.15 Ampacity of conductors rated 0 – 2000 volts:
(1) Tables: Ampacities for conductors shall be permitted to be determined by tables as
provided in 310.15(B)
(2) Selection of Ampacity. Where more than one ampacity applies for a given circuit
length, the lowest value shall be used.
Exception: If the lower ampacity section of the conductor length is less than 10 feet
and less than 10% of the total length, the higher ampacity may be used.

If more than 10 feet or 10% of the conductor is exposed to a higher
temperature than the rest of the conductor length, the entire conductor length
must be derated to that higher temperature.
(3) Temperature Limitation of Conductors. The temperature rating of the full conductor
circuit length may not be exceeded during its continuous operation.
e.g. A conductor rated 75C (167F) may not use in a location that will
experience a temperature of 76C (168F).
• That applies to the equipment as well.
145
PV source circuit conductor open air ampacity ratings
Table 310.15(B)(17) Allowable Ampacities of Single-Insulated Conductors Rated Up to and Including
2000 Volts in Free Air, Based on Ambient Temperature of 30°C (86°F)*
American
Wire Gauge
 PV modules typically have #12 PV wire (USE-2) rated 35a to 40a.
 Field installed cables are all #10 PV Wire (USE-2) rated 50a to 55a
Derating these conductors is not necessary since source circuits require less than 15a
146
Conductor Ampacities in Conduit
PV output conductors and all other conductors ran in conduit.
Table 310.15 (B)(16) gives amperages for up to 3 conductors in a raceway at 30°C.
or
 Select minimum current rating based on temperature rating of equipment
147
Article 690.31(A) Wiring Systems.
For ambient temperatures exceeding 30°C (86°F), conductor ampacities shall be corrected in
accordance with Table 690.31(A).
 This table is for PV source and output conductors only.
 For all other conductors use the table referenced on the next slide.
NOTE: The two tables correction factors are the same on identical temperatures.
148
Table 310.15 (B)(2)(a) Ambient temperature correction factors based on 30°C (86°F)
Table 310.15(B)(3)(c)
Conduits exposed to sunlight or on rooftops
 Select the derate column according to
the conductor.
Raceways shall be installed 7/8” above the
roof.
• If installed less than 7/8” above the roof
33C (60F) shall be added to the ambient
temperature before applying the derate
factor in Table 310.15(B)(2)(a)
149
Table 310.15(B)(3)(a) Adjustment Factors for More Than Three Current-Carrying
Conductors in a Raceway or Cable.
Conductor ampacity must be derated for more than three current-carrying conductors
together in a conduit or cable for more than 24”.
 For DC, both positive and negative are current carrying conductors.
 For AC, the neutral is considered current carrying only if the circuit contains nonlinear loads.
150
Review: Calculations for Conductor Sizing and Derating
PV DC conductors:
1.
Isc x 1.25 = Maximum current (maximum continuous current)
2.
Max current x 1.25 = minimum conductor rating - Table 310.15(B)(16)
e.g. PV array with module Isc 9a
Isc 9a x 1.25 x = 11.25a max continuous string current
11.25a x 1.25 = 14.06a = output conductor ampacity requirement
3.
Select conductor based on equipment and conductor temperature rating.
Table 310.15(B)(16) shows #14 is adequately rated in the all columns.
4.
Apply derate factors for temperature and # of conductors in a conduit.
Table 69031(A) for temperature and Table 310.15(B)(3)(a) for # of conductors
e.g. Ambient temperature of 110°F and 4 conductors in a conduit (2 strings)
Equipment and conductor are 90 rated
#14 is rated 25a in the 90C column
25a x .87 x .80 = 17.4a
17.4 a is greater than 11.25a max current calculated in #2 above.
151
Voltage Drop Calculations
 In AC systems, voltage drop should be no more than 3% and shall not be more than 5%.
This is because as voltage drops amperage increases.
 PV array DC output voltage drop does not affect amperage. We try to limit voltage drop
to less than 2% and no more than 3% in order to maximize system output.
Table 8 lists conductor resistance per 1000 feet for conductors in DC circuits.
• Find the wire size and corresponding resistance (Ohms/kFT) uncoated for copper.
• Determine the operating current (STC Imp x 80% or NOC Imp)
VD = operating current x one way distance x 2 ÷ 1000 x Ohms/kFT
STC-NOC
Slide 10
VD% = VD ÷ operating voltage (NOC Vmp x # of modules in string)
Table 9 has resistances per 1000 feet for AC conductors.
• Use inverter continuous current listed on data sheet
3-phase calculation
VD = operating current x one way distance x 1.732 ÷ 1000 x Ohms/kFT
1.732 is the square root of 3 (√3)
152
Table 8 DC Conductor Properties
153
Table 9 Alternating Current Resistance
154
Review: Voltage Drop Calculations
First gather the necessary information to make the calculation.
1. Find the operating current.
•
Module STC Imp x 80% or NOC Imp (single string or combined strings)
•
For inverter output, the continuous current is used.
2. Determine the length of the conductor in the circuit.
3. Look up the Ohms/kFT in Chapter 9 Table 8 for DC or Table 9 for AC.
4. Find the operating voltage
•
Module NOC Vmp on data sheet x # in series
•
Inverter or premises AC nominal voltage
5. Put the information in the formula and calculate
Example:
Module NOC Imp 7.76a and Vmp 29v
13 modules in a string
Conductor length 60’ #14 AWG
VD = 7.76a x 60’ x 2 x 3.14Ω/kFT ÷ 1000 = 2.92v
String voltage = 29v x 13 in series = 377v
VD% = 2.92v ÷ 403v = .0074 or .74%
155
Overcurrent Protection Requirements
690.9 Overcurrent Protection.
(A) Circuits and Equipment. PV system dc circuit and inverter output conductors and
equipment shall be protected against overcurrent. Overcurrent protective devices are
required where currents exceed the rated capacity of equipment or conductors.
Exceptions: A PV circuit overcurrent device is not required in the following conditions.
(1) Where there are no parallel external source circuits such as other module strings,
batteries or back-fed current from inverters.
 This would be a single string of modules connected to a string inverter or a
single module connected to either a DC-DC converter or a micro-inverter.
(2) The short-circuit currents from all sources do not exceed the ampacity of the
conductors and overcurrent device rating for the PV module or dc-to-dc converter.
e.g. PV module with Isc of 6a and series fuse rating of 15a.
Two strings connected in parallel without a fuse. 2 x 6a = 12a
12a is less than 15a so no fuse is required.
 With ungrounded systems, only one of the two DC conductors requires a OCD or fuse
a long as a disconnect is in place that disconnects both conductors simultaneously.
156
690.9 Overcurrent Protection cont.
(B) Overcurrent Device Ratings. OCDs used with PV DC circuits must be listed for use with
PV systems and are to be sized in 1, 2 or 3 below.
(1) Not less than 125 percent of the maximum currents calculated in 690.8(A).
e.g. Isc x 125% x 125%
(C) Photovoltaic Source and Output Circuits. A single overcurrent protective device shall be
permitted to protect the PV modules and conductors of each source circuit or the
conductors of each output circuit.
•
All overcurrent devices OCDs shall be placed in the same polarity for all circuits
within a PV system.
•
The OCD shall be accessible but shall not be required to be readily accessible.
Art. 240.6(A) Fuses and Fixed-Trip Circuit Breakers.
Table 240.6(A) Standard Ampere Ratings for Fuses and Inverse Time Circuit Breakers
DC fuses under 15a: 1a – 10a and 12a
The standard ampere ratings for fuses 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110,
125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600,
2000, 2500, 3000, 4000, 5000, and 6000 amperes.
157
DC Overcurrent Protection
Check the listing for the OCD used with PV system DC circuits. It must be listed for PV DC
circuits.
The UL 2579 class of fuses include Class R, J and M.
 Recommended fast blow fuses for PV source and output circuits
 Large capacity high voltage breakers are becoming more of a
standard on PV systems with central inverters.
150 volt DC breakers
Used primarily on battery systems
600 volt DC
M-class fuses
1 -30 amps
600 volt DC
R-class fuses
30 to 350 amps
158
Overcurrent Device OCD Rating and Conductor Rating
240.4(B) Devices Rated 800 Amperes or Less.
The next higher standard overcurrent device rating (above the ampacity of the
conductors being protected) shall be permitted to be used, provided all of the following
conditions are met:
240.4(C) Overcurrent Devices Rated over 800 amperes (1MW inverters)
Where the overcurrent device is rated over 800 amperes, the ampacity of the
conductors it protects shall be equal to or greater than the rating of the overcurrent
device defined in 240.6.
240.4(D) Small conductors
Unless specifically permitted in 240.4(E) or (G), the overcurrent protection shall not
exceed that required by ratings listed below after any correction factors for ambient
temperature and number of conductors have been applied.
•
14 AWG Copper.
15 amp OCD
•
12 AWG Copper.
20 amp OCD
•
10 AWG Copper.
30 amp OCD
 The conductor size can be now smaller than shown above for each OCD.
159
Exercise Example: (Use tables on next page)
[-----------------------max temp. 37ºC------------------------] [----------max temp. 30ºC-----------]
PV array
J-box
Combiner
Inverter
AC panel
DC & AC
Terminals
Rated 75ºC
36 - 250w modules: 3 strings: 12 in series
Voc 36v : Vmp 30.5v : Isc 8.9a : Imp 8.2a
8kW 1-Phase reverse current protected
7600w 240v 32a
1. Give the string max current rating.
2. Give the string fuse requirement.
3. Give the string conductor ampacity requirement.
4. Select the minimum size conductor from the j-box to the combiner.
5. What is the ampacity rating of the selected conductor?
6. Derate the string conductors for conditions.
7. What is the OCD requirement of the inverter output?
8. Size the inverter output conductor.
160
Table 310.15 (B)(16) 3 conductors in a raceway at 30°C.
Table 690.31(A) Correction Factors
Table 310.15(B)(3)(a) Adjustment for More Than Three Current-Carrying Conductors in a Raceway.
161
Exercise Example answers:
[-----------------------max temp. 37ºC------------------------] [----------max temp. 30ºC-----------]
PV array
J-box
Combiner
AC panel
Inverter
DC & AC
Terminals
Rated 75ºC
36 - 250w modules: 3 strings: 12 in series
Voc 36v : Vmp 30.5v : Isc 8.9a : Imp 8.2a
8kW 1-Phase reverse current protected
7600w 240v 32a
1. Give the string max current rating. 8.9a x 1.25 x = 11.25a
2. Give the string fuse requirement. 11.25 x 1.25 = 13.9 15a OCD
Table 240.6(A)
3. Give the string conductor ampacity requirement. 11.25 x 1.25 = 13.9 14a
4. Select the minimum size conductor from the j-box to the combiner. #14
5. What is the ampacity rating of the selected conductor? 20a
Table 310.15(B)(16) 75º
6. Derate the string conductors for conditions. 20a x .91 x .80 = 14.56a > 11.25a
Table 310.15 (B)(2)(a) and
Table 310.15(B)(3)(a)
7. What is the OCD requirement of the inverter output? 32a x 1.25 = 40a
8. Size the inverter output conductor. 32 x 1.25 = 40a #8
240.6(A)
Table 310.15(B)(16) 75º
162
Review on Conductor and Overcurrent Device selection
 Table 400.4 provides conductor properties and conditions of use.
 The minimum bending radius for USE and USE-2 is 5x the conductor diameter.
 PV source and output maximum current is 125% of the STC short circuit current Isc.
 A professional electrical engineer can make an alternate calculation using the highest
3-hour irradiance for the location; it can be no less than 70% of (125% of STC) method.
 For interactive inverters the continuous current is the listed max current.
 Conductors and circuit requirements must be rated no less than 125% of continuous current.
 Conductor selection is based on the ampacity under the temperature rating of the conductor
and the connected equipment. The lowest temperature column is to be selected.
 Conductor ampacity must also be derated if 10% or 10’ of its length is exposed to
conditions other than the ratings of Table 310.15(B)16.
 PV source and output conductor ampacities are derated for temperature using Table
690.41(A) if they are exposed to temperatures greater than 30C (68F).
 Other conductor ampacities are derated using Table 310.15(B)(2)(a)
 Conductors in conduit less than 7/8” above a roof and exposed to sunlight must add 33C
163
Review: Conductor and Overcurrent Device selection
 Conductors ran in conduit for more than 24 inches must be further derated in Table
310.15(B)(3)(a) if there are more than 3 current carrying conductors in the conduit.
 Voltage drop occurs over a length of wire when current passes through it. Table 8 is used for
DC circuits to select conductor ohms/kFT for this calculation.
e.g. VD = operating current x one way distance x 2 ÷ 1000 x Ohms/kFT
 AC circuits use Table 9 for the same formula. 3-phase circuits use the following formula.
VD = operating current x one way distance x 1.732 ÷ 1000 x Ohms/kFT
 For high ampacity requirements parallel conducts can be used instead of a single conductor.
• The parallel conductors can be no smaller than 1/0 AWG.
• They must be the same length, size, type and be terminated in the same manner.
 Overcurrent devices (OCD) are sized 125% grated than the continuous current. Table
240.6(A) provides increments for OCDs.
 Conductor ampacities of the following must match the OCD.
•
14 AWG Copper.
15 amp OCD
•
12 AWG Copper.
20 amp OCD
•
10 AWG Copper.
30 amp OCD
164
Most common violations
1. Bending radius to tight for USE-2 and PV wire.
2. Selection of the wrong type of conductor insulation for underground conduit.
3. Violations of small conductor and OCD maximums. (#14 – 15a, #12 – 20a, #10 – 30a)
4. Failing to follow manufacturer’s required ampacities and OCDs in manual.
Addressing this potential violation.
1. The minimum bending radius is 5x the conductor diameter for USE-2; several high
voltage conductors such as PV wire have a bending radius of 8x.
− If you can’t fit a coffee cup into the curve, it is in violation.
2. THHN is sometimes used and it is OK for moist locations but not wet. THWN-2 or
XHHW-2 are commonly used for underground. List it on the permit.
3. The conductor-OCD violation occurs most often with residential inverter output
conductors. For these three conductors, the OCD must be determined and the conductor
is selected and can be no smaller than shown in Article 240.4(D). List it on the permit.
4. The manufacture may override the NEC calculations for conductors and OCDs; if so
the installer must adhere to those specifications.
− This is most common with battery system inverter input and output.
165
Conductor Protection
690.31 Methods Permitted.
(A) Wiring Systems. Where PV source and output circuits operating at voltages greater than
30 volts are installed in readily accessible locations, circuit conductors shall be guarded
or installed in Type MC cable or in raceway.

Ground mounted arrays with source wires lower than 8’ must provide guarding.
Definition: Guarded. Covered, shielded, fenced, enclosed, or otherwise protected
by means of suitable covers, casings, barriers, rails, screens, mats, or platforms to
remove the likelihood of contact by persons to a point of danger.
Examples:
Residential ground mounted array
• A 4’’ fence 6’’ away from the array.
• Metal or 30 year UV rated fabric mesh preventing access to the source conductors.
Commercial ground and roof mount
• 6’ fence 10’ from the array for ground mounts
• Roof array with unauthorized access will require a barrier or enclosed racking.
e.g. Solar Dock racking is totally enclosed.
166
PV source conductor securing and supporting
690.31 (C) Single -Conductor Cable
(1) General. Single conductor USE-2 and “PV wire” are permitted for PV source and
output conductors and shall be installed according to 338.10(B)(4)(b) and 334.30.
(2) Cable Trey. The use of cable trey used outdoors is permitted when the cables are
supported at least every 12 inches and secured at least every 4.5 ft.
Article 338.10 Uses Permitted.
(B)(4)(b) Exterior Installations. Service-entrance cable used for feeders or branch
circuits, where installed as exterior wiring, shall be installed in accordance with Part I
of Article 225. The cable shall be supported in accordance with 334.30.
334.30 Securing and Supporting.
Nonmetallic-sheathed cable shall be supported or secured 4½ ft and within 12 in. of
every outlet box, junction box, cabinet, or fitting.
 PV cables must be secured within 12” of the module j-box and any other J-box.
• This is almost impossible to achieve with some module j-box locations.
 The 4 ½ ft requirement should be reduced to 24” .
167
Protection Against Fire From DC Conductors
Art.690.31 Wiring Methods
(G) Direct-Current Photovoltaic Source and Output Circuits on or in a Building.
Where direct-current photovoltaic source or output circuits of a utility-interactive inverter
from a building-integrated or other photovoltaic system are run inside a building or
structure, they shall be contained in metal raceways from the point of penetration of the
surface of the building or structure to the first readily accessible disconnecting means.
The wiring methods shall comply
with the additional installation
requirements in (1) through (4)
listed on the next page.
This area
 FMC and MC cable are the most
common metallic conduit used
for residential installations.
 EMT and IMC are commonly used on commercial buildings
168
Routing of PV Source Conductors
690.31(G) Direct-Current PV Source and DC Output Circuits on or in a Building.
(2) Flexible Wiring Methods. Flexible metal conduit FMC shall be protected if smaller
than ¾ inch.
Metal clad conduit MC shall be protected if smaller than 1 inch by substantial guard
strips that are at least as high as the raceway or cable.
 It is common to run one or the other of these two in residential attics and
basements.
¾” and larger FMC cable
needs no protection
1” and larger MC cable
needs no protection
169
Article 690.31(G) continued
(3) Marking or Labeling Required. A label “Warning: Photovoltaic Power Source” shall
be installed where:
(1) Exposed raceways, cable trays, and other wiring methods
(2) Covers or enclosures of pull boxes and junction boxes
(3) Conduit bodies in which any of the available conduit openings are unused
(4) Marking and Labeling Methods and Locations. The labels shall be visible and rated
for their environment. The labels shall be placed on all PV wireways at all observable
points and at intervals of no more than 10 feet.
 This is only on PV source and output circuits that are on or inside a building.
The labels shall be reflective, and all letters shall be capitalized and shall be a minimum
height of 9.5 mm (3⁄8 in.) in white on a red background.
170
Which Conduit for the Application?
PVC is usually used for ground mounted systems with underground feeds.
•
When PVC is used for above ground feeds the issue of expansion should be considered
due to extremes of temperature.
•
If PVC is used when exposed to physical damage it must be protected or Schedule 80 is
required.
FMC or MC is usually used for residential interior installation wile commercial typically
use EMT for interior applications.
EMT, IMC or RMC are used on most rooftop installations
•
EMT uses compression connectors and although they are rated for over 250v as
grounding pathway they are subject to connector failure if expansion couplings are not
used in exterior installations with long runs.
•
If EMT is used in locations where it will be exposed to physical damage it must be
protected.
•
IMT or RMC are typical used for large commercial exterior applications; they are both
rated against physical damage and have low expansion rates due to temperature swings.
Annex C provides conduit fill for # of conductors and type of conductor insulation.
171
Review: PV Array Output Conductor Protection
 PV source and output circuit conductors operating over 30v must be protected from ready
access by unauthorized persons. They must be guarded by boxes, conduit or some type of
obstruction to prevent accidental contact.
 Where multiple different circuits are ran in the same raceway or conduit, they must be
separately identified at junction boxes.
• In cable treys the separate identification must occur no less than every 6 feet.
 PV wire and USE-2 source conductors must be secured within 12 inches of j-boxes and
every 4 ½ ft in between.
 PV array source and output conductors ran on or in a building must be ran in metal
raceways up to the first readily accessible disconnect.
• If MC cable is ran in accessible locations, it must be protected if smaller than 1”
• If FMC conduct is ran in accessible locations, it must be protected if smaller than 3/4”
 PV source and output conduit ran on or in building must be marked with the following.
WARNING: PHOTOVOLTAIC POWER SOURCE
172
Most common violations
1. Residential ground mounted array source conductors are often not adequately protected
from unauthorized ready access.
2. Separate circuits are not adequately separated or identified at j-boxes or pull boxes.
3. Residential rooftop source conductors are not adequately secured to modules or railing.
4. The label Warning: Photovoltaic Power Source is often forgotten on residential installs.
5. PVC conduit used for PV source and output circuit conductors.
Addressing this potential violation.
1. If you can reach the conductors by hand without removing the barrier or standing on a
ladder, it is in violation.
2. This is common in j-boxes without terminations. Have the contractor remove the j-box
cover to inspect for multiple circuits that are not identified or separated.
3. It is usually possible to look at the array from the plane of the roof; a high powered
flashlight may be necessary to see wire sags under the array.
4. Look for the label on PV array output circuits attached to the building or ran into the
building. This easy to see or not see as the case may be.
5. PVC is OK from the inverter output but not to the inverter input if the conduit enters
the structure. This will only occur on residential installations.
173
Protection from Arcs and Requirements for First Responders
 2011 Arc-fault Protection Requirements
690.11 Arc-Fault Circuit Protection (Direct Current).
Photovoltaic systems operating at 80 volts or greater, shall be protected by a listed PV arcfault circuit interrupter or other system components listed to provide equivalent protection.
• The system shall detect and interrupt arcing faults resulting from a failure of continuity
in a conductor, connection, module, or other component in the PV system dc circuits.
• 2014 NEC also required these on ground mounted systems.
Exception: For PV systems not installed on or in buildings:
• PV output circuits and dc-to-dc converter output circuits that are direct buried, installed
in metallic raceways, or installed in enclosed metallic cable trays are permitted without
arc-fault circuit protection.
• Detached structures whose sole purpose is to house PV system equipment are also
permitted without arc-fault circuit protection.
 The device must meet the UL1699B standard.
 It may be located in inverters, combiners, module optimizers or in DC wiring
fuse boxes or charge controllers for battery based systems.
174
 Protection Against Arc-Flash
110.16 Arc-Flash Hazard Warning.
(A) General. Any location other than
dwelling units where service may be
performed while the conductive parts are
energized must be marked to warn of arcflash potential.
The warning sign(s) or label(s) shall comply with 110.21(B).
(B) Service Equipment For 1200a rated
equipment, a label with the following must
be in place.
(1)
Nominal voltage
(2)
Available fault current at overcurrent
devices OCD
(3)
clearing time of OCD
(4)
Date label was applied
 A 50kW string inverter would be a class 1.
175
Arc flash classifications
Example formula: Combiner, DC disconnect or Recombiner box arc-flash formula
(Pmax x 125% x 2 second ÷ (4πD²) x 3 x .239cal/J) = cal/cm²
• D = distance
18” (45.5cm) arc-flash standard distance
• 3 is a multiplier used for enclosures with open front only.
• 1.2 cal/m² and greater require arc-flash protection
e.g. 50kW X 125% x 2 ÷ 26002 x 3 x .239 = 3.45cal/cm²
176
Service equipment fault current marking
110.24 Available Fault Current (A) Marking. Service equipment for other than dwelling
units must field-mark the max available fault current even if it is not assessable when live.
 This would only be required if the commercial PV system is connected to the line side
of the meter as a separate service. e.g. (Georgia Power Tariff program)
 When transformers are used this calculation also includes the impedance of the
transformer.
e.g. Transformer kW ÷ 1000 ÷ voltage ÷ 1.732 ÷ impedance
500kW x 1000 ÷ 480v ÷ 1.732 ÷ .05Ω = 12,028a fault current
Open
Lockable Disconnects
110.25 Lockable Disconnecting Means. If a
disconnecting means is required to be “lockable
open” elsewhere in this Code, it shall be capable
of being locked in the open position under all
conditions.
Lockable
177
 Rapid Shutdown of the DC Side of the PV System
690.12 Rapid Shutdown of PV Systems on Buildings
PV system circuits installed on or in building shall include a rapid shutdown function to
reduce shock hazard for emergency responders in accordance with 690.12(A) through (D).
Exception: Ground mounted PV system circuits that enter buildings dedicated only for PV
system equipment shall not be required to comply with 690.12.
 The following is the 2014 version which has been changed or moved in the 2017 version.
1. Requirements for controlled conductors shall apply only to PV system conductors of more
than 1.5 m (5 ft) in length inside a building, or more than 3 m (10 ft) from a PV array.
2. Controlled conductors shall be limited to not more than 30 volts and 240 volt-amperes
within 10 seconds of rapid shutdown initiation.
3. Voltage and power shall be measured between any two conductors and between any
conductor and ground.
4. The rapid shutdown initiation methods shall be labeled in accordance with 690.56(C).
5. Equipment that performs the rapid shutdown shall be listed and identified.
 2017 changes and additions (A) through (D) are on the following slides
178
2017 NEC version of 690.12(A) through (D).
(A) Controlled Conductors. Requirements for controlled conductors shall apply to all PV array
source and output circuits.
(B) Controlled Limits. The array boundary is defined here as 305 mm (1 ft) from the array in
all directions.
(1) Outside the Array Boundary. Controlled conductors located outside the boundary or
more than 1 m (3 ft) from the point of entry inside a building shall be limited to not
more than 30 volts within 30 seconds of rapid shutdown initiation.
•
Voltage shall be measured between any two conductors or conductor to ground.
(2) Inside the Array Boundary. The PV system shall comply with one of the following:
(1) The PV array shall be listed or field labeled as a rapid shutdown PV array.
•
The PV array shall be installed and used in accordance with its instructions.
(2) Controlled conductors shall be limited to not more than 80 volts within 30
seconds of rapid shutdown initiation.
•
Voltage is between any two conductors or conductor to ground.
(3) PV arrays with no exposed wiring or conductive parts installed more than 2.5 m
(8 ft) from exposed grounded parts are not be required to comply with (B)(2).
 690.12(B)(2) shall become effective January 1, 2019.
179
Outside the boundary reduced to 30v within 30 sec.
• 2014 boundary is 5’ inside or 10’ outside the building
• 2017 boundary is 3’ inside or 1’ outside the building
Inside the boundary reduced to 80v will not take effect until January 1st 2019
Credit: May/June SolarPro article written by Bill Brooks
180
2017 NEC version of 690.12(A) through (D) cont.
(C) Initiation device. The device shall initiate the rapid shutdown function of the PV
system. Its “off” position shall indicate that the rapid shutdown function has been
initiated for all PV systems connected to that device.
•
For one-family and two-family dwellings, an initiation device(s) shall be located at
a readily accessible location outside the building.
•
The initiation device(s) shall consist of at least one of the following:
(1) Service disconnecting means
(2) PV system disconnecting means
(3) Readily accessible switch that plainly indicates whether it is “off” or “on”.
 This may be the PV system AC disconnect, DC disconnect or a remote
activation device that is listed specifically for rapid shutdown of PV circuits.
• As with all service disconnects, the number cannot exceed more than 6 separate
switches to disconnect all PV system circuits for a single service customer.
 The would most like only occur with a central inverter that has multiple
combiner boxes containing rapid shutdown devices.
• Since string inverters are typically used, this situation is unlikely.
181
(D) Equipment. Equipment that performs the rapid shutdown functions, other than listed
disconnect switches, circuit breakers, or control switches, shall be listed for providing
rapid shutdown protection.
Informational Note: Inverter input circuit conductors often remain energized for up to 5
minutes with inverters not listed for rapid shutdown.
 This refers to the 2019 requirement of 80v or less inside the 1 ft. boundary
 All commercial string inverters located within 1 ft. of the array are in compliance
(until 2019) if the AC disconnect is placed in a readily accessible location.
AC disconnects shut down microinverters within 1 foot of the array
Listed Rapid Shutdown devices disconnect
DC circuits within 1 ft. of the array
182
Review: Protection with Arcs, Faults and First Responders
 AFCI devices are required on all roof mounted PV arrays operating at 80v and over.
 Arc-flash warnings are required on any location other than dwelling units where service
may be performed on live electrical parts.
 Service equipment other than for dwelling units must be marked for the available fault
current even if it is not accessible when live.
 PV systems installed buildings must be equipped with a rapid shutdown function.
• The 2014 version allows 10’ from the array boundary to the location of the disconnect
for the exterior and 5’ to the interior.
• The 2017 version allows 1’ from the array boundary to the location of the disconnect
for the exterior and 3’ to the interior.
− The disconnect must be remotely activated from a readily accessible location.
NOTE:
• Micro-inverters all perform the rapid shutdown function upon loss of AC power.
• SolarEdge inverters all perform this function by use of their module PV optimizers.
• Tigo electronics has a UL listed device that snaps onto the module junction box and
provides the rapid shutdown function to several inverter brands.
183
Most common violations
1. Arc-fault device missing from battery based system.
2. Arc Flash warning not posted on commercial AC switchgear.
3. Rapid shutdown switch not labeled and posted.
Addressing this potential violation.
1. Arc-fault devices are standard in residential interactive inverters and most commercial
interactive inverters.
− With battery systems, the device may be in the charge controller of a separate
device placed in a combiner box or the DC output box. Require the contractor to
list where the device is located on the permit and/or drawings.
2. There may not be an arc flash potential with small commercial system but the medium
sized 100kW to 1MW are likely to require them. Since string inverters are used for nonutility scale systems, the DC side usually has low potential when serviceable.
3. This is the #1 mostly likely violation! Interactive systems usually comply with the
device since residential rooftop systems are either micro-inverters or SolarEdge
optimized and commercial string inverters are located on the roof with the PV array.
− The 2014 requirement for posting the label was very vague. The 2017 is very
clear; they switch that initiate the shutdown must be marked.
184
Disconnect Requirements from the PV System
III. Disconnecting Means
690.13 Photovoltaic System Disconnecting Means. Means shall be provided to disconnect
the PV system from all wiring systems including power systems, energy storage
systems, and utilization equipment and its associated premises wiring.

The former reference to ungrounded conductors has been removed in the 2017
690.13 (A) Location. The PV System disconnecting means shall be installed at a readilyaccessible location.
 This 2014 exception no longer applies in the 2017 NEC since rapid shutdown
must occur within 1’ of the PV array.
Informational Note: PV systems installed in accordance with 690.12 address the
concerns related to energized PV array DC conductors entering a building.
 PV system disconnect means does not always refer to PV array DC conductors.
• The following sides will identify various locations of the PV system
disconnect means for different systems.
185
Interactive PV system disconnect means
Micro‐inverters or AC modules
Micro-inverters or AC modules: The AC disconnect is the PV system disconnect means.
PV array DC
Disconnect
String inverters also use an AC disconnect as the PV system disconnect means.
Drawing credit: May/June SolarPro article written by Bill Brooks
186
PV systems with energy storage disconnect means
Energy Storage
Disc.
DC coupled PV systems with energy storage: The DC disconnect the PV system disconnect.
AC coupled PV systems with energy storage:
• The interactive inverter AC disconnect the PV system disconnect.
Drawing credit: May/June SolarPro article written by Bill Brooks
187
690.13 (B) Marking. Each PV system disconnecting
means shall plainly indicate whether in the open (off)
or closed (on) position and be permanently marked
“PV SYSTEM DISCONNECT” or equivalent.
Additional markings shall be permitted based
upon the specific system configuration.
For PV system disconnecting means where the line and load terminals may be energized
in the open position, the device shall be marked with the following words or equivalent:
 This is most likely to occur on systems with
central inverters with disconnects from multiple
DC combiner boxes.
188
(C) Suitable for Use: If the PV system is connected to the supply side of the service
disconnecting means as permitted in 230.82(6), the PV system disconnecting means
shall be listed as suitable for use as service equipment.

The minimum rating for supply side disconnects is 60a
(D) Maximum number of disconnects. Each PV system disconnecting means shall
consist of not more than six switches or six sets of circuit breakers.
•
A single PV system disconnecting means shall be permitted for the combined
ac output of one or more inverters.

This article was reworded for clarity. The purpose of this requirement is
to provide quick shutdown of a PV system.
(E) Ratings. The PV system disconnecting means shall have ratings sufficient for the
maximum available short-circuit current, and voltage connect to it.
(F) (1) Simultaneous Disconnection. The PV system disconnecting means shall
simultaneously disconnect the PV system conductors from all other conductors.
•
Types: Externally operable switch, circuit breaker, or other approved means.
•
A dc PV system disconnecting means shall be marked for use in PV systems or
be suitable for backfeed operation.
This includes functionally grounded conductors.

189
690.13(D) illustrated
Each of these inverters requires a separate overcurrent device which is also a disconnect.
• Since there are more than 6, a combined circuit disconnect must be provided.
• In this picture there are 16 inverters with OCD disconnects; they must be combined
into groups of 3 or more to reduce the total number of disconnects to 6 or less.
190
Art.690.15 Disconnection of Photovoltaic Equipment. Isolating devices shall be provided to
isolate PV modules, ac PV modules, fuses, dc-to-dc converters inverters, and charge
controllers from all conductors that are not solidly grounded.
 This refers to connectors such as PV module polarized type and micro-inverter
connectors rated less than 30a.
 Circuits of 30a and greater must use a listed load-rate disconnecting means.
(A) Location. Isolating devices shall be installed within sight of and within 10 ft of the
equipment.
•
An equipment disconnecting means shall be permitted to be located further away if it
remotely activates a disconnect located within 3 m (10 ft) of the equipment.
(B) Interrupting Rating. An equipment disconnecting means shall have an interrupting rating
sufficient for the maximum short-circuit current and voltage available at the terminals.
•
An isolating device shall not be required to have an interrupting rating.
These isolating devices can be non-load-rated.
Micro-inverter isolating connectors
Load rated disconnect
PV module isolating connectors
191
690.15(A)
 Modules are connected to each other or
electronic equipment with listed isolating
devices (polarized connectors)
 Micro inverters are located beneath PV
modules and are attached to each other
with listed isolating connectors.
Readily accessible
192
690.15(C) Isolating Device. An isolating device shall not be required to simultaneously
disconnect all current-carrying conductors of a circuit.
• The isolating device shall be one of the following:
(1) A connector meeting the requirements of 690.33 and listed for the use.
 This reference is to polarized connectors that are touch safe with latching
connections and are listed for the use.
(2) A finger safe fuse holder
 Both devices at right meet
this designation.
(3) An isolating switch that requires a tool to open
(4) An isolating device listed for the intended application
• Non-load-rated isolating device shall be marked
“Do Not Disconnect Under Load” or “Not for Current Interrupting.”
193
(D) Equipment Disconnecting Means. An equipment disconnecting means shall
simultaneously disconnect all current carrying conductors that are not solidly grounded
of the circuit to which it is connected.

The grounded conductor in a grounded PV system must be switched with the
ungrounded conductor if it is grounded with a GFDI. (BIG CHANGE)
• An equipment disconnecting means shall be safely externally operable.
• The disconnect shall indicate whether in the open (off) or closed (on) position, and be
lockable in the open (off) position.
• An equipment disconnecting means shall be one of the following devices:
(1) A manually operable switch or circuit breaker
(2) A connector meeting the requirements of 690.33(E)(1)

Be rated for interrupting current without hazard to the operator
(3) A load break fused pull out switch
(4) A remote-controlled circuit breaker that is operable locally and opens
automatically when control power is interrupted

This would most likely be a rapid shutdown switch.
 This 2017 NEC sub-article (D) has replaced 2014 NEC article 690.17.
 Note the requirement to disconnect both + and – conductors in all systems
194
690.15(D) illustrated
Grounded PV systems have historically required the grounded conductor to be marked
white or grey and placing a disconnect in this conductor was very restrictive.
• Now the grounded conductor is not to be marked white or gray and it must be
disconnected simultaneously with the ungrounded conductor.
NOTE: The grounded
conductor is functional
grounded, not solidly
grounded.
2017 NEC grounded and ungrounded PV
2014 NEC and earlier grounded PV
195
Review: Disconnect Requirements
 It is required to have a means to disconnect the PV system from all other components and
systems.
 The PV system disconnect means shall be located at a readily accessible location.
• With interactive PV system that location is at the interactive inverter disconnect.
• With battery based PV system that location is the PV array DC disconnect.
 Each PV system disconnect must be marked
PV SYSTEM DISCONNECT
 For disconnects where the line and load terminals can remain energized in the off position,
the following notice must be posted.
WARNING: ELECTRIC SHOCK HAZARD
TERMINALS ON THE LINE AND LOAD SIDE
MAY BE ENERGIZED IN THE OPEN POSITION
 The PV system disconnect means shall consist of not more than 6 switches.
 The PV system disconnecting means must be externally operable.
 The PV system disconnecting means must disconnected all conductors that are not solidly
grounded simultaneously.
 Isolating devices such as polarized PV connectors serve as non-load breaking disconnects.
 Isolating devices must be located within-sight-of and within 10’ of the equipment.
196
Review: Disconnect Requirements, cont.
 The 2014 code does not allow for a disconnect in the grounded conductor.
 The 2017 code requires a disconnect in the grounded conductor if it is a functional ground
such as in a GFDI fuse.
• With PV circuits, the + and – conductors must be simultaneously disconnected. The
conductors should be marked red (+) and black (-) even if one is functionally grounded.
197
Most common violations
1. Disconnects may serve several functions and require several labels. One of the required
labels is usually missing when this is the case.
2. More than 6 PV system disconnects are more common now with commercial string
inverter systems.
Addressing this potential violation.
1. Interactive systems use the AC disconnect as PV system disconnect (1); it is most likely
the rapid shutdown switch as well (2). The disconnect must also list the AC operating
voltage and current (3). The utility will also place a label on the disconnect. (3 labels +)
− DC coupled battery PV systems use the DC disconnect as the PV system disconnect
(1); it may also be the rapid shutdown switch (2). The disconnect must also show the
array max voltage and current and the charge controller max current (3). (3labels)
2. This is easy to see since the AC disconnect is located next to the inverter. It they all feed
into a dedicated switchgear panel, a main AC switch will disconnect them all.
198
PV System Labels and Plaques
110.21(B) Field-Applied Hazard Markings.
(1) The marking shall adequately warn of the hazards using effective words and/or colors
and/or symbols or any combination thereof.
Informational Note: ANSI Z535.4-2011, Product Safety Signs and Labels, provides
guidelines for suitable font sizes, words, colors, symbols, and location for labels.
(2) The label shall be permanently affixed to the equipment or wiring method and shall not
be hand written.
Exception: Portions of labels or markings that are variable, or that could be subject to
changes, shall be permitted to be hand written and shall be legible.
 All PV labels should be printed.
(3) The label shall be of sufficient durability to withstand the environment involved.
 Consider the life of the PV system.
NOTE: Several companies offer labeling serviced: “PV Labels”, “HellermannTyton” and
some of the solar distributors are now offering this service.
199
2014 Labeling Requirement for PV Array DC Disconnects
690.53 Direct-Current Photovoltaic Power Source.
A permanent label for the direct-current photovoltaic power source indicating items (1)
through (5) shall be provided by the installer at the photovoltaic disconnecting means:
(1) Rated maximum power-point current
(2) Rated maximum power-point voltage
(3) Maximum system voltage
(open voltage on coldest day of year)
(4) Maximum circuit current
(5) Maximum rated output current of the
charge controller (if installed)
MAXIMUM CIRCUIT CURRENT
#1 is the STC Imp x # of strings in parallel
#2 is STC Vmp x # of module is series
#3 is Voc x # of modules is series x the coldest day temperature coefficient factor.
#4 is to be the maximum continuous current (Isc x 125%)
#5 is the max current listed on the charge controller
 The following slide represents the 2017 version of this article.
200
2017 Labeling Requirement for PV Array DC Disconnects
690.53 Direct-Current Photovoltaic Power Source.
A permanent label for the direct-current photovoltaic power source indicating items (1)
through (3) shall be provided by the installer at each load rated photovoltaic disconnecting
means:
• Each DC power source must have this label
(1) Maximum system voltage
(open voltage on coldest day of year)
(2) Maximum circuit current
(3) Maximum rated output current of the
charge controller (if installed)
MAXIMUM CIRCUIT CURRENT
#1 is Voc x # of modules is series x the coldest day temperature coefficient factor.
#2 is to be the maximum continuous current (Isc x 125%).
#3 is the max current listed on the charge controller.
 The other two values we removed because they are insignificant to inspectors,
first responders or service personnel..
201
Labeling on the Inverter AC Disconnects
690.54 Interactive System Point of Interconnection. All interactive system(s) points
of interconnection with other sources shall
be marked at an accessible location at the
disconnecting means as a power source and
with the rated ac output current and the
nominal operating ac voltage.
 This is the utility voltage and the inverter
rated continuous current.
202
Identification of Power Sources 690.56
690.56(A) Facilities with Stand-Alone Systems. Any structure or building with a
photovoltaic power system that is not connected to a utility service source and is a
stand-alone system shall have a permanent plaque or directory installed on the exterior
of the building or structure at a readily visible location acceptable to the authority
having jurisdiction.
•
The plaque or directory shall indicate the location of system disconnecting means
and that the structure contains a stand-alone electrical power system.
•
The marking shall be in accordance with 690.31(G).
 Readily visible indicates a location that is visible from the main approach to the
facility. i.e. as you drive up
THIS STRUCTURE CONTAINS
A STAND ALONE
ELECTRICAL PV SYSTEM
9.5 mm (3⁄8 in.)
letting
PV SYSTEM DISCONNECT
IS LOCATED
________________
White letters on
red background
203
 Identification of Power Sources
690.56(B) Facilities with Utility Services and PV Systems.
Removed from 690 in the 2017 NEC because it is duplicated in Article 705.10
705.10 Directory. A permanent plaque or directory denoting the location of all electric
power sources disconnecting means on or in the premises shall be installed at each service
equipment location and at the disconnect(s) for each electric power production source
capable of being interconnected.
• The marking shall comply with 110.21(B).
 If the PV system AC disconnect is
located next to the service equipment
location, the label on the disconnect is
sufficient.
 The directory can be in writing instead
of a drawing.
• Using both is a better form of
communication.
204
Effective until 2017 NEC is adopted
2014 version of 690.56(C): Rapid Shutdown Label Requirement
690.56(C) Facilities with Rapid Shutdown. Buildings or structures with both utility and
PV system complying with 690.12 shall have a permanent plaque or directory
including the following wording:
The plaque shall be reflective with all letters capitalized and having a minimum height
of 3/8 inches in white on red background.
No designation for the location of the label
205
Effective on January 1st 2019
2017 version of 690.56(C): Rapid Shutdown Label Requirement
690.56(C) Buildings with Rapid Shutdown. Buildings with PV systems shall have
permanent labels as described in (1) through (3) below.
(1) Rapid Shutdown Type. The type of rapid shutdown shall be labeled as in (a) or (b):
(a) For PV systems that shut down the array internally and conductors leaving the
array: Use the following language
SOLAR PV SYSTEM EQUIPPED
WITH RAPID SHUTDOWN
Minimum
3/8” letter height
Black letters on
yellow background
Minimum
3/16” letter height
Black letters on
white background
Label shall be located no more than 3 ft from the service disconnecting means.
206
Effective when 2017 NEC is adopted
(1) Rapid Shutdown Type. The type of rapid shutdown shall be labeled as described in (a)
or (b) below:
(b) For PV systems that only shut down conductors leaving the array:
SOLAR PV SYSTEM EQUIPPED
WITH RAPID SHUTDOWN
Minimum
3/16” letter height
Black letters on
white background
Minimum
3/8” letter height
White letters on
Red background
SOLAR ELECTRIC
PV PANELS
The labels in (1)(a) and (b) shall include a simple diagram of a building with a roof.
• The diagram shall have sections in red to signify areas of the PV system that are not
shut down when the rapid shutdown switch is operated.
Label shall be located no more than 3 ft from the service disconnecting means.
207
690.56(C)(2) Buildings with More Than One Rapid Shutdown Type. Buildings with both types
of rapid shutdown, a detailed plan view diagram of the roof shall be provided showing
each different PV system and a dotted line around areas that remain energized after the
rapid shutdown switch is operated.
(3) Rapid Shutdown Switch. A rapid shutdown switch shall have a label located on or no
more than 1 m (3 ft) from the switch that includes the following wording:
RAPID SHUTDOWN SWITCH
FOR SOLAR PV SYSTEM
Minimum
3/8” letter height
White letters on
Red background
 The labels required in (C)(1)(a) and (b) are plaques that can be placed on the switch.
 The switch itself must have its own label as shown above.
208
Review: PV System Labels and Plaques
 Article 110.21(B) provides guidance for lettering on labels and plaques
 The PV array DC disconnect must label max system voltage and max circuit current on it. If
a charge controller is present, its max output current must also be listed.
• The 2014 version also required operating current and operating voltage to be listed.
 The AC disconnect must label the operating current and operating voltage of the interactive
source “inverter(s)”.
 Facilities with stand-alone systems must have a plaque on the exterior of the structure that
shows the location of the system disconnecting means.
 Facilities with interactive systems must have a plaque located at the service and the
disconnecting locations that shows the location of all power source disconnecting means.
 Buildings with rapid shutdown shall have a label within 3’ of the main service disconnect.
 The rapid shutdown switch must be labeled:
RAPID SHUDOWN SWITCH FOR SOLAR PV SYSTEM
209
Most common violations
1. Hand written labels or labels that do not meet the ANSI standard for size and the
environment.
2. Multimodal systems don’t usually have the plaque for stand-alone PV system disconnect.
3. The plaque for rapid shutdown within 3’ of the service is usually missing because the
2014 code did not include this requirement.
4. Rapid shutdown switch label missing from AC disconnect when micro-inverters are used.
Addressing this potential violation.
1. Hand written labels should only be allowed on a battery system critical AC loads center.
− Preprinted labels are available from several suppliers; HellermannTyton supplies the
industry with every PV label required and label printing products.
2. Multimodal system installers usually provide the interactive disconnect switch and label
but not the stand-alone label denoting the location of that disconnect.
3. The 2017 requirement for the plaque within 3’ of the service should be enforced ASAP.
4. The 2014 NEC introduced the requirement for rapid shutdown but did not require the
switch to be labeled if rapid shutdown occurred with micro-inverters or PV optimizers.
− This 2017 labeled switch requirement should also be enforced ASAP.
210
Interactive Utility Connection
690.59 Connection to Other Sources. PV systems connected to other sources shall be installed in
accordance with Parts I and II of Article 705.
Art. 705.12 Point of Connection
(A) Supply Side. An electric power production source shall be permitted to be connected to the
supply side of the service disconnecting means as permitted in 230.82(6).
• The sum of the ratings of all overcurrent devices connected to power production sources
shall not exceed the rating of the service.
e.g. Residential:
200a service at 240v = 48,000w x 80% = 38.4kW
15kVA transformer = 15,000w (15kW) Net metering limit is 10kW
Commercial: Line side connections are either under Georgia Powers tariff
or Qualifying facility. Net metering limit is 125% of peak usage.
211
Art 705.12 (A) Supply Side.
Art 230.82 Equipment Connected to the Supply Side of Service Disconnect.
(6) Solar photovoltaic systems, fuel cell systems, or interconnected electric power
production sources.

Connecting to the supply side requires permission from the utility and must comply
with the space requirements of the service box.
705.31 Location of Overcurrent Protection. For supply side connections in 705.12(A), the
location of the OCD shall be within 3 m (10 ft) of the connected to the service.
212
Customer Side Connection
705.12 (B) Load Side. The output of an interconnected electric power source shall be
permitted to be connected to the load side of the service disconnecting means of the other
source(s) at any distribution equipment on the premises.
(1) Dedicated Overcurrent and Disconnect. Each source connection shall be made with
dedicated overcurrent protection.
(2) Bus and Conductor Ampere Rating. Feeders, taps and busbars must be rated 125% of the
power source (inverter) continuous current.
1) Feeders: b. An overcurrent device on the load side of the power source connection
shall be rated not greater than the ampacity of the feeder.
 The connection point is often the service lugs for the conductors.
2) Taps: The tap shall be rated no less than 125% of the inverter continuous current.
 This refers to the inverter OCD.
 A tab bonds directly to the conductor or lugs.
213
Customer Side Connection
705.12 (B) (2)
Option 1
3)Busbars: One of the following four methods shall be used to determine the ratings of
busbars in panelboards.
a) The sum of 125 percent of the inverter(s) output circuit current and the rating of
the OCD protecting the busbar shall not exceed the ampacity of the busbar.
 This is when the inverter OCD is placed anywhere along the busbar
without regard to the location of the main OCD.
e.g. 200a busbar with 200a main OCD = zero margin for the inverter OCD
200a busbar with 150a main OCD = 50a margin for the inverter OCD
PV Disconnect
DC Breaker & GFDI
PV Array
AC
Output
PV Utility
Disconnect
50
+
-
Main AC
Panel
200a bus
150
1234kWH
Utility
Meter
Disconnect
50a limit
214
705.12 (D) (2)
Option 2
3) Busbars
(b) Where two sources, one a utility and the other an inverter, are located at opposite
ends of a busbar that contains loads (branch circuit breakers), the sum of the ampere
ratings of overcurrent devices supplying power to a busbar (main OCD + inverter
OCD(s) shall not exceed 120 percent of the rating of the busbar rating.
•
A permanent warning label shall be applied to the distribution equipment adjacent
to the inverter back-fed breaker that displays the following or equivalent wording:
2017 NEC: Replace “Inverter”
with “Power Source”
e.g. 200a busbar with 200a main OCD = 40a margin for inverter OCD
200a x 120% = 240a - 200a OCD = 40a
215
Example 1
705.12(D)(2)(3)(b)
Option 2
The busbar ampere rating can be oversized by 120% as long as the inverter OCD is placed at
the opposite end of the busbar from the main OCD.
Example:
200 amp busbar with 200 amp main OCD
200 x 1.20 = 240 amps – 200 amp OCD = 40 amps PV OCD
The inverter OCD must be sized at 125% of the continuous current.
40 ÷ 1.25 = 32 amp inverter maximum continuous current.
 32a x 240v = 7.68kW inverter
Main AC Panel
PV Array
PV Combiner
Disconnect
AC Out
DC in
Tap allowed
on exterior to
full capacity.
PV Utility
Disconnect
Inverter & GFDI
200
+
40
Utility
Meter
40a limit
216
Example 2
705.12(D)(2)(3)(b)
Option 2
The busbar rating is often greater than the main OCD when the main OCD is not located in
the main AC panel.
Example:
225 amp busbar with 200 amp main OCD
225 x 1.20 = 270 amps – 200 amp OCD = 70 amps PV OCD
The inverter OCD must be sized at 125% of the continuous current.
70 ÷ 1.25 = 56 amp inverter maximum continuous current.
 56a x 240v = 13.4kW inverter
Tap not
allowed
PV Disconnect
DC Breaker & GFDI
PV Array
AC
Output
PV Utility
Disconnect
Main AC
Panel
225a bus
+
200
70
-
1234kWH
Utility
Meter
Disconnect
70a limit
217
705.12 (D) (2)
Option 2 – center fed panels
3) Busbars
(D) A connection at either end, but not both ends, of a center-fed panelboard in
dwellings shall be permitted where the sum of 125 percent of the power source(s)
output circuit current and the rating of the overcurrent device protecting the busbar does
not exceed 120 percent of the current rating of the busbar.
Main AC Panel
PV Array
PV Combiner
Disconnect
AC Out
DC in
PV Utility
Disconnect
Utility
Meter
Inverter & GFDI
+
200
40
-
 Make the same calculation and panel label used in (B) Option 2
218
Tapping Into the Load Side
Art. 705.12(D)(2)(1-2) Connecting to feeders and making taps
Using the 10 foot tap rule, the PV utility disconnect would need to be within 10’ of the tap
and also be fused to protect the conductors beyond the 10’ tap area.
240.21 (B) Feeder Taps. Conductors shall be permitted to be tapped, without
overcurrent protection at the tap, to a feeder as specified in 240.21(B)(1) through (5).
(1)
Not over 10’ in length
The conductor taps must be adequately rated for the load and if they leave the tap
container they must be rated no less than 1/10th of the main overcurrent device.
Tap Area allowed
to full capacity
PV Disconnect
DC Breaker & GFDI
PV Array
AC
Output
PV Utility
Disconnect
OCD
Main AC
Panel
OCD
1234kWH
+
-
Utility
Meter
Disconnect
219
Listed taps with visible inspection capacity.
Polaris
Match service feeder size and equal tap
220
705.12 (D)
(3) Markings. Equipment containing overcurrent devices in circuits supplying power to a
busbar or conductor supplied from multiple sources shall be marked to indicate the
presence of all sources.
 This is simply labeling the load center with the inverter OCDs.
(4) Suitable for Backfeed. Breaker shall be rated for back-feed.
 Most breakers are rated for back-feed. If it is not, it will be marked “Line and Load”.
(5) Fastening. Listed plug-in-type circuit breakers backfed from electric power sources that are
listed and identified as interactive shall be permitted to omit the additional fastener
normally required by 408.36(D) for such applications.

Generators and battery based inverter with outputs that are self-developed must
have locking devices on the breakers;

Interactive inverter output is dead without utility connection (anti-islanding).
221
705.40 Loss of Primary Source. Upon loss of primary source, an electric power
production source shall be automatically disconnected from all ungrounded
conductors of the primary source and shall not be reconnected until the primary
source is restored.

This the IEEE1547 anti-islanding protocol required of all interactive inverters.
705.100 Unbalanced Interconnections.
(A) The unbalanced load for multiple single phase inverters connected to 3-phase AC
systems shall not exceed 3%.

Single phase inverters have three AC output options; 240v (L1, L2, Neutral)
208v (L1, L2, Neutral) and 277v (L1, Neutral).
• Any of these configurations will need to be in groups of three in order to
maintain balanced conditions.
222
Review Service Connections
 With supply side connections the capacity of the PV system overcurrent devices cannot
exceed the rating of the service.
 For supply side connections the location of the PV system OCD must be within 10 ft of the
service connection.
 Load side connections allow four options to interconnect.
1. The busbar must be rated for the main OCD plus the OCD from the inverter.
2. The busbar may be exceeded by 120% as long as the inverter OCD is placed at the
opposite end from the main OCD. (one or the other with a center fed busbar).
3. Full capacity of the busbar can be used if the branch circuit OCDs and the inverter
OCDs do not exceed 100% of the busbar capacity.
4. A commercial engineered system is allowed to calculate with PV OCD fault studies.
 Taps can be made with 100% of the feeder capacity if the tap is made between the main
OCD in the load center and the OCD at the service location.
 Breakers used to backfeed load centers must be rated for back feed.
 Loss of utility power must shut the inverter down from selling into the grid. UL1741
223
Most common violations
1. Load side inverter OCD is oversized for the busbar of the main AC load center.
2. Load side inverter OCD is not placed at the opposite end of the load center busbar from
the main OCD.
3. The label is not place next to the inverter OCD.
4. Improperly installed tap.
Addressing this potential violation.
1. This happens with contractors who are new to the industry and have not been trained.
− Multiply the busbar rating x 120% - main OCD = max inverter OCD
2. As with #1, the installer would be new and untrained.
3. This is the most common violation; forgetting the label. This is for option #2.
4. There are UL listed taps that are questionable because it is difficult to verify the
competency of the tap penetration.
− See the tap examples on the next slide.
224
Labeling and Plaque Example, Interactive with micro-inverters
PV SYSTEM
DISCONNECT
(a)
(b)
1
RAPID SHUTDOWN SWITCH
FOR SOLAR PV SYSTEM
(c)
+
+
+
POWER SOURCE
DIRECTORY
(e)
(d)
J-box
1234kWH
+
+
+
PV array
AC Panel
Meter
Front door
1. PV array AC disconnect
(a) PV system disconnect label
(b) AC disconnect label
(c) Rapid shutdown Switch Driveway
label
(d) Plaque denoting location of rapid
shutdown switch
(e) Power source disconnect directory
225
Labeling and Plaque Example, Interactive with string inverter
PV SYSTEM
DISCONNECT
(a)
(b)
3
2
Inverter
RAPID SHUTDOWN SWITCH
FOR SOLAR PV SYSTEM
(c)
POWER SOURCE
DIRECTORY
1
(e)
+
+
+
(d)
+
+
+
PV array
AC Panel
Front door
1. Photovoltaic power source label
2. PV array DC disconnect
(a) PV system DC disconnect label
(b) Possible Rapid shutdown switch label
1234kWH
J-box
Meter
3. PV array AC disconnect
(a) PV system disconnect label
(b) AC disconnect label
Driveway
(c) Rapid
shutdown Switch label
(d) Plaque denoting location of rapid
shutdown switch
(e) Power source disconnect directory
226
+
+
+
+
+
+
+
+
+
+
+
+
1
2(a)(b)(c)
+
+
+
+
+
+
+
+
+
+
+
+
1
2(a)(b)(c)
1234kWH
2(a)(b)(c)
AC Panel
Labeling and Plaque Example, Commercial string inverters
Meter
(d)
(e)
+
+
+
+
+
+
+
+
+
+
+
+
1
2(a)(b)(c)
+
+
+
+
+
+
+
+
+
+
+
+
1
2(a)(b)(c)
+
+
+
+
+
+
+
+
+
+
+
+
1
PV array
1. PV array DC disconnect label
2. PV array Stand-alone AC disconnect
(a) PV system disconnect label
(b) AC disconnect label
(c) Rapid shutdown Switch label
(d) Plaque denoting location of rapid
shutdown switch
(e) Power source disconnect directory
227
Review with question and answer
SOLAIRGEN
School of Solar technology
www.solairgen.com
119 Highway 52 West
Dahlonega, GA 30533
706-867-0678
info@solairgen.com
Battery systems slide 251
228
Addendum 1:
Solar PV with Energy Storage Systems.
• These systems are gaining in momentum in many parts of the world and the U.S. Georgia
will see a strong growth as well in the next few years.
• At this time most PV installations in Georgia are interactive without energy storage. This
will most likely change slowly at first and the progressively more rapid.
− The reason for energy storage system growth is not because we have a poor
electrical grid because we don’t.
− Interactive residential systems send most of the solar PV energy back into the grid
each day and at a time when load demand is not high.
− Energy storage will make the grid stronger and make PV system energy more
valuable to utilities.
229
Code sections covering energy storage (2017 NEC)
Article 690 PV systems:
• Addresses batteries and energy storage; it also refers to other sections of the code that set
minimum standards for installing battery systems and components.
Article 480 Storage Batteries:
• The article specifically addresses all batteries.
Article 706 Energy Storage Systems: New for systems operating over 60v DC
• This article consists mostly of what was previously in 690 with a few changes and
additions plus it duplicates 480 but specifically to battery systems.
Article 710 Stand-Alone systems: New
• Covers other sections taken from 690 in previous NEC editions.
Article 712 Direct Current Micro-Grids: New
• This is the same as a multimodal systems. Micro-grids are potentially much larger and
more complex than standard multimodal systems.
230
Requirements for All Battery Systems
480.10 Battery Locations.
(A) Ventilation. Provisions appropriate to the battery technology shall be made for
sufficient diffusion and ventilation of gases from the battery, to prevent the
accumulation of an explosive mixture.
Informational Note No. 1: See NFPA 1-2015, Fire Code, Chapter 52, for ventilation
considerations for specific battery chemistries.
 Most sealed batteries do not gas and do not require this type of ventilation.
(C) Spaces About Battery Systems. For battery racks, there shall be a minimum clearance
of 25 mm (1 in.) between a cell container and any wall or structure on the side not
requiring access for maintenance.
(E) Egress. Door(s) intended for entrance to, and egress from, rooms designated as
battery rooms shall open in the direction of egress (out) and shall be equipped with
listed panic hardware.

Panic hardware is not typically required with residential systems.
(F) Piping in Battery Rooms. Gas piping is not permitted in dedicated battery rooms.
231
690.10 Stand-Alone Systems. The wiring system connected to a stand-alone system shall be
installed in accordance with 710.15.
 See next slide
690.55 Photovoltaic Power Systems Employing Energy Storage. Photovoltaic power systems
employing energy storage shall also be marked with the maximum operating voltage,
including any equalization voltage and the polarity of the grounded circuit conductor.
2014 label
MAXIMUM OPERATING VOLTGE
_____
EQULIZATION VOLTAGE
_____
POLARITY OF GROUNDED CONDUCTOR
_____
GROUNDING (+, -, ungrounded)
______
690.55 Photovoltaic Systems Connected to Energy Storage Systems. The PV system output
circuit conductors shall be marked to indicate the polarity where connected to energy storage
systems.
 Red for positive and black for negative
232
Article 710 Stand-Alone Systems
710.6 Equipment Approval. All equipment shall be listed or field labeled for the intended use.
 All electrical equipment installed in the U.S. must be listed equipment. i.e. UL listed
• Except for lead acid batteries
Moved from 690
710.15(A) Supply Output. Power supplied by the inverter(s) to premises wiring systems
shall be permitted to have less capacity than the calculated load.
− The capacity of the stand-alone supply shall be equal to or greater than the load
posed by the largest single piece of electrical equipment connected to the system.
− Calculated general lighting loads shall not be considered as a single load.
 This allows the inverter(s) to be rated less than a typical calculation would
require and use load shed features. The minimum requirement is to have enough
capacity to run the largest single load continuously.
(B) Sizing and Protection. The output circuit conductors from these inverters shall be
sized based on the sum of their output ratings.
e.g. 2 - 8kW inverters with rated output of 240v, 33A require conductors and OCDs
based on 66a continuous current.
Moved from 690
233
710.15 (E) Back-fed Circuit Breakers. Plug-in type back-fed circuit breakers connected to
a stand-alone inverter output in either stand-alone or utility-interactive systems shall be
secured in accordance with 408.36(D).
• Circuit breakers that are marked “line” and “load” shall not be backfed.
408.36 (D) Back-Fed Devices. Plug-in-type overcurrent protection devices that are
backfed and used to terminate field-installed supply conductors shall be secured
in place by an additional fastener that requires a means other than spring snap type
pressure to hold the breaker in place when the cover is removed.
Retaining
Screw
Overcurrent Breaker
Secured retainer
 Locking devices for residential AC load centers are very limited.
 Commercial load centers are usually bolted to the busbar.
234
408.36 (D) Back-Fed Devices, illustrated Bolt-in Load Centers
Inverter manufacturer’s sell these load centers; they are designed for the application with
bolt-in breakers.
Outback Radian GSLA
235
Direct Current System Grounding
250.162(A) Two-Wire, Direct-Current Systems. A 2-wire, dc system supplying premises
wiring and operating at greater than 60 volts to 300 volts shall be grounded.
250.164 Point of connection for DC systems
(B) On-Premises Source. Where the dc system source is located on the premises, a
grounding connection shall be made at the following:
(2) The first system disconnection means or overcurrent device
250.167 Direct-Current Ground-Fault Detection.
(A) Ungrounded Systems. Ground-fault detection shall be required for ungrounded systems.
 A ground fault detector on the battery side of a charge controller would serve both
PV array ground fault and battery ground fault detection.
(B) Grounded Systems. Ground-fault detection shall be permitted for grounded systems.
(C) Marking. Direct-current systems shall be legibly marked to indicate the grounding type at
the dc source or the first disconnecting means of the system. The marking shall be of
sufficient durability to withstand the environment involved.

Ungrounded ESS will require ground fault detection on the DC battery system.
236
Review: Requirement for All Battery Systems
 A spacing of 1” around individual battery cells is considered minimum.
 Adequate ventilation is required on all batteries and batteries that gas out are required to
have a method of removing those gases from the building.
 Doors on dedicated battery rooms must open away from the room; some also require panic
hardware.
 Gas piping is not allowed in dedicated battery rooms.
 Battery inverters suppling power to a load center must be rated for the largest load.
 Stand-alone inverter output circuit breakers must be securely fastened to the load center.
 The DC input current rating to a battery inverter is calculated at the lowest DC voltage.
This section covers all battery systems of all voltages.
The next section covers energy battery systems over 60v and is specific tot 2017 NEC.
• The 2014 NEC required most of what is in this section for all battery system voltages.
• Prior to the 2017 NEC the max voltage for residential battery systems was 50v (nominal).
• The maximum battery system voltage for 2017 NEC is 100v (maximum).
237
Most common violations
1. Residential energy storage PV systems regularly violate several of these areas. The ones
of serious concern in this section are:
a) Adequate ventilation for all battery types and external ventilation for flooded leadacid batteries (FLA).
b) Gas piping in the battery room
c) Breakers not being secured in the load center
2. Commercial energy storage systems are engineered; violations are rare.
Addressing this potential violation.
1. Residential energy storage systems that are pre-engineered as a package will have fewer
violations. Self-built systems may have several.
a) Only FLA batteries pose a real threat; require the contractor to specify type on permit.
b) The battery room is often shared with several other appliances. Water pipes and
HVAC ducts over the batteries is a violation. Gas pipes in the room are dangerous.
c) With pre-engineered systems , the DC and AC overcurrent device centers will all be
bolt-in type. Self-built system may feed directly into the AC load center. This is where
the unsecured breaker violation occurs.
2. Require the commercial contractor to submit detailed drawings.
238
Battery system operating over 60 volts
690 Part VIII. Energy Storage Systems (ESS) formerly “Storage Batteries”
690.71 General. An energy storage system connected to a PV system shall be installed
in accordance with Article 706.
Article 706 Energy Storage Systems (operating at over 60v DC)
706.1 Scope. This article applies to all permanently installed energy storage systems (ESS)
operating at over 50 volts ac or 60 volts dc that may be stand-alone or interactive.
706.30(A) Dwelling Units. An ESS for dwelling units shall not exceed 100 volts between
conductors or to ground.
Exception: ESS that restrict access to live parts during routine maintenance may exceed 100v.
Equipment listed for use:
706.5 Equipment. Monitors, controls, switches, fuses, circuit breakers, power conversion
systems, inverters and transformers, energy storage components, and other components
of the energy storage system other than lead-acid batteries, shall be listed.
• Self-contained ESS shall be listed as a complete energy storage system.
 Renewable energy storage batteries that are part of a larger battery bank are UL
recognized instead of UL listed.
239
Disconnect Requirements
480.7(A) Disconnecting Means. A disconnecting means shall be provided for all ungrounded
conductors derived from a stationary battery system with a voltage over 60 volts dc.
The disconnect shall be readily accessible and located within sight of the battery system.
Moved from 480
 This was over 50v in the 2014 NEC.
706.7(A) ESS Disconnecting Means. A disconnecting means shall be provided for all
ungrounded conductors derived from an ESS.
A disconnecting means shall be readily accessible and located within sight of the ESS.
Moved from 480

See 706/7(E) for actual distance required from the ESS and the disconnect.
(B) Remote Actuation. Where controls to activate the disconnect are not located within
sight of the system, the disconnect shall be lockable in the open position.
• The location of the controls shall be field marked on the disconnecting means.
 This would be like a rapid shutdown device located on the exterior of the building.
• Not required but a good idea
240
706.7(B) Remote Actuation: Illustrated
5’
Disconnect
Battery bank
Inverter
Within sight
of disconnect
Exterior switch for
ESS disconnect.
Remote activated disconnect
Inverter
Battery bank
Placards are applied to each disconnect indicating the location of the other.
241
Energy Storage System rating
Moved from 690
706.7(D) Notifications. The following must be marked on the battery disconnecting means.
(1) Nominal energy storage system (ESS) voltage
(2) Maximum available short-circuit current derived from the ESS
(3) The associated clearing time or arc duration based on the available short-circuit
current from the ESS and associated overcurrent protective devices
(4) Date the calculation was performed
 #3 above should be given by the battery manufacturer. Just multiply the Isc times the
number of battery strings in parallel.
• An alternate method is to multiplying the 3 amp/hour rate by 20.
 #4 is listed on the overcurrent device.
Polarity Marking
690.55 Photovoltaic Systems Connected to Energy Storage Systems. The PV system output
circuit conductors shall be marked to indicate the polarity where connected to energy
storage systems.
 This refers to the standard of Red for + and Black for –
242
706.7(D) Notifications: Illustrated
Energy Storage System Disconnect
Nominal ESS voltage
______
Maximum short-circuit current
______
OCD arc clearing time
______
Date the calculation
______
243
Disconnect Requirements
706.7(E) Partitions and Distance. Where energy storage system input and output terminals are
more than 1.5 m (5 ft) from connected equipment, or where the circuits from these
terminals pass through a wall or partition, they shall comply with the following:
Moved from 690
(1) Fused or unfused disconnecting means shall be provided at the energy storage system
end of the circuit.
(2) If the disconnect in (1) above is not within site of the equipment, a second disconnect
must be installed at the equipment location.
(3) Where fused disconnects are used, the line of the terminals are toward the energy
storage system.
(4) If the above disconnect is located within the battery vault with vented gasses the
disconnect must be listed for hazardous locations.
(5) If two disconnects are required as indicated in (1) and (2) above, a placard must be
placed at both locations indicating the location of the other disconnect.
 This is required for all equipment connected directly to the ESS.
• A single disconnect to a DC equipment box would suffice.
244
706.7(E) Partitions and Distance. Illustrated
5’
Inverter
Disconnect
Battery bank
Additional disconnect required here
Within sight
of disconnect
Room partition
Disconnect
Battery bank
More than 5’ and not within
site of the disconnect
Inverter
Within sight
of disconnect
Placards are applied to each disconnect indicating the location of the other.
245
Connection to other energy sources
706.8 Connection to Other Energy Sources. Connection to other energy sources shall comply
with the requirements of 705.12.
 In short this article states that interactive systems with energy storage must follow
the same requirements as interactive systems without energy storage.
The interactive connection
from this inverter must
comply with 705.12
246
Directory
 This code section is a duplicate of 705.10 Directory
706.11 Directory. A permanent plaque or directory denoting the location of all electric
power sources disconnecting means on or in the premises shall be installed at each service
equipment location and at the disconnect(s) for each electric power production source
capable of being interconnected.
• The marking shall comply with 110.21(B).
 If the PV system AC disconnect is
located next to the service equipment
location, the label on the disconnect is
sufficient.
 The directory can be in writing instead
of a drawing.
• Using both is a better form of
communication.
247

This a close duplicate of 690.56(A) with the blue highlighted exceptions
706.11(B) Facilities with Stand-Alone Systems. Any structure or building with a
photovoltaic power system that is not connected to a utility service source and is a
stand-alone system shall have a permanent plaque or directory installed on the exterior
of the building or structure at a readily visible location acceptable to the authority
having jurisdiction.
•
The plaque or directory shall indicate the location of system disconnecting means
and that the structure contains a stand-alone electrical power system.
•
The marking shall comply with 110.21(B).
 Readily visible indicates a location that is visible from the main approach to the
facility. i.e. as you drive up
THIS STRUCTURE CONTAINS
A STAND ALONE
ELECTRICAL PV SYSTEM
9.5 mm (3⁄8 in.)
lettering
PV SYSTEM DISCONNECT
IS LOCATED
________________
White letters on
red background
248
Part III. Electrochemical Energy Storage Systems
706.30 ESSs that are comprised of sealed and non-sealed cells or batteries or systems that
are not components within a listed product.
Moved from 690 and changed regarding voltage
(A) Dwelling Units. An ESS for dwelling units shall not exceed 100 volts between conductors
or to ground.
(B) Disconnection of Series Battery Circuits. Battery circuits subject to field servicing and
exceeding 240 volts nominal between conductors or to ground, shall have provisions to
disconnect the strings into segments not exceeding 240 volts (nominal) for maintenance.
• Non–load-break bolted or plug-in disconnects shall be permitted.
(C) Storage System Maintenance Disconnecting Means. ESS exceeding 100 volts between
conductors or to ground shall have a disconnecting means, accessible only to qualified
persons, that disconnects ungrounded and grounded circuit conductor(s) in the electrical
storage system for maintenance.
•
A non–load-break-rated disconnecting means shall be permitted to be used.
(D) Storage Systems of More Than 100 Volts. On ESS exceeding 100 volts shall be permitted
to operate with ungrounded conductors.
•
A ground-fault detector and indicator must installed to monitor for ground faults
within the storage system.
3/16/2017
249
Moved from 690
Connector and Terminal Ratings for Battery Cables
706.32 Battery Interconnections. Flexible cables, as identified in Article 400, in sizes 2/0
AWG and larger shall be permitted within the battery enclosure from battery terminals
to a nearby junction box or DC load center.
•
These cables shall be listed and identified as moisture resistant.
•
Flexible, fine-stranded cables shall only be used with terminals, lugs, devices, or
connectors in accordance with 110.14.
Art. 110.14 Electrical Connections. This article states that connectors must be identified for
the specific use. Fine stranded cables require lugs specific to their size.

The lugs on the left are rated specific for fine stranded cables.
Fine strand cable lugs
Polaris Grey are rated for fine stranded cable.
Polaris Black must be sized exact.
250
Review: Battery Systems over 60 volts
 Article 706 is dedicated to energy storage systems ESS operating over 60v.
 The maximum ESS voltage for dwelling units is 100v formerly 50v in 2014 and earlier.
 A disconnecting means is required for ESS operating over 60v formerly 50v.
 Systems operating over 60v must be grounded unless they contain a ground fault device.
 Systems 60v or less and over 100v may be ungrounded if they have ground fault detection.
 A label is required on the ESS to identify nominal voltage, short circuit current, the
clearing time of the OCD and the date the calculation was performed.
 PV circuits must be marked with their polarity when connected to systems with ESS.
 A disconnect and OCD must be placed within sight of and within 5’ of the ESS.
 Disconnects must be placed within sight of the equipment being disconnected.
 If two disconnects are placed between an ESS and a piece of equipment, a placard must be
installed at each location indicating the location of the other.
 Interactive battery inverters must follow the interconnection rules of 705.12
 A directory must be installed showing the location of all interconnected power sources.
 Stand-alone facilities must display a plaque showing the location of the disconnect means
for the electrical power system.
251
Review: Battery Systems over 60 volts, cont.
 The max current for ESS equipment is the nameplate rating of the equipment.
 DC overcurrent device must be rated for DC, the voltage and current as well as the
automatic interrupt capacity (AIC) of the equipment being protected.
 ESS that use the interactive connection to divert excess PV energy away from the batteries
and into the grid, must have a secondary method of protecting the batteries from
overcharge in case the grid fails. The same is true if a DC diversion controller is used.
 ESS DC operating over 240v must have disconnecting means that section it to 240v or
less.
 ESS DC operating over 100v may be ungrounded if they contain a ground fault device.
 Fine stranded cables require connectors listed specific to their size, current and voltage.
252
Most common violations
1. The disconnecting means may be further than 5’ from the battery bank.
2. Most residential battery banks are ungrounded and not protected by ground fault
protection devices.
3. Battery bank labeling may be insufficient.
4. The directory at the meter denoting the location of the stand-alone disconnecting means
is usually missing.
Addressing this potential violation.
1. Most new factory made battery containers provide the option of integrated disconnect and
OCD. Otherwise the inverter is the first location of the disconnect/OCD.
If the conductors are in metal conduit, this is not an issue; exposed or PVC would be.
•
2. Require the method of grounding and battery fault protection on the permit so it can be
verified during inspection.
3. The label should have Battery nominal voltage, short circuit current and polarity marked
on it at a minimum.
4. Labeling is usually a problem with PV system installations;
this label is the most often omitted.
Require a list of labels on the permit.
•
THIS STRUCTURE CONTAINS
A STAND ALONE
ELECTRICAL PV SYSTEM
PV SYSTEM DISCONNECT
IS LOCATED
________________
253
Labeling and Plaque Example, (DC Coupled) PV with Energy Storage
(b)
RAPID SHUTDOWN SWITCH
FOR SOLAR PV SYSTEM
(a)
(c)
(2)
PV SYSTEM
DISCONNECT
Controller
Critical Load Panel
Main Load Panel
(5)
Rapid shutdown
device
(a)
(5)
+
+
(3)
+
+
+
+
+
(a)
+
1234kWH
Inverter
Utility
Meter
(a)
(b)
THIS STRUCTURE CONTAINS
A STAND ALONE
ELECTRICAL PV SYSTEM
+
+
+
PV SYSTEM DISCONNECT
IS LOCATED
________________
(1)
+
+
+
(d)
POWER SOURCE
DIRECTORY
Front door
1. Photovoltaic power source label
2. PV array DC disconnect
(a) PV system disconnect label
(b) Rapid shutdown switch label
(c) PV system DC disconnect label
(d) Plaque for PV system disconnect
3. PV array Stand-alone AC disconnect
(a) PV system disconnect label
(b) Plaque for Stand-alone disconnect
4. Interactive AC disconnect
(a) Interactive AC disconnect label
5. ESS voltage and Isc label
254
Labeling and Plaque Example, (AC Coupled) PV with Energy Storage
RAPID SHUTDOWN SWITCH
FOR SOLAR PV SYSTEM
(2)
(3)
PV SYSTEM
DISCONNECT
(b)
(c)
(a)
Interactive
inverter
Critical Load Panel
Main Load Panel
(5)
Rapid shutdown
device
(a)
(6)
+
(4)
+
+
+
+
+
+
(a)
+
1234kWH
Inverter
Utility
Meter
(a)
(b)
THIS STRUCTURE CONTAINS
A STAND ALONE
ELECTRICAL PV SYSTEM
+
+
+
PV SYSTEM DISCONNECT
IS LOCATED
________________
(1)
+
+
+
(d)
POWER SOURCE
DIRECTORY
Front door
1. Photovoltaic power source label
2. PV array DC disconnect
3. Interactive Inverter AC disconnect
(a) PV system disconnect label
(b) Rapid shutdown switch label
(c) PV system AC disconnect label
(d) Plaque for Rapid shutdown
4. PV array Stand-alone AC disconnect
(a) PV system disconnect label
(b) Plaque for Stand-alone disconnect
5. Bimodal Interactive AC disconnect
(a) Interactive AC disconnect label
6. ESS disconnect
(a) Voltage and Isc label
255
Review with question and answer
SOLAIRGEN
School of Solar technology
www.solairgen.com
119 Highway 52 West
Dahlonega, GA 30533
706-867-0678
info@solairgen.com
256