03/22/2021
ICP SCCR & UL 508A Supplement SB
Joe Pavia, P.E.
Field Application Engineer
Bussmann division
Contact info:
Phone: 317-665-1956
Email: joempavia@eaton.com
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Passing the UL508A MTR
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Agenda
• Industrial Control Panel SCCR & UL 508A
Supplement SB
•
•
•
•
•
NEC Requirements
Definitions
Determining component ratings
Use of current limiting devices
Interactive session on analyzing the assembly SCCR of
example control panels.
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NEC
Industrial Control Panels
&
Industrial Machinery
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What is short-circuit current rating (SCCR)?
NEC Article 100 Definition
Short-Circuit Current Rating. The prospective symmetrical fault
current at a nominal voltage to which an apparatus or system is able
to be connected without sustaining damage exceeding defined
acceptable criteria.
Hazards of insufficient SCCR
Available fault
current: 20 kA
•
•
•
Shock: Enclosure becomes energized from conductors
pulling away from terminations
Fire: Explosive power blows off door exposing flames
and molten metal to exterior
Projectile (shrapnel): Enclosure door explosively blows
open emitting failing device debris
SCCR:
5 kA
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Another misapplication
YouTube video
https://www.
youtube.com
/watch?v=8a
9B9jgVmys
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Section 110.10, Circuit Impedance, Short-Circuit
Current Ratings, and Other Characteristics
Slide:
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Industrial control panel definition
NEC Article 100 Definition
Industrial Control Panel. An assembly of two or more components
consisting of one of the following:
(1) power circuit components only, such as motor controllers,
overload relays, fused disconnect switches, and circuit breakers;
(2) control circuit components only, such as push buttons, pilot lights,
selector switches, timers, switches, and control relays;
(3) a combination of power and control circuit components.
The industrial control panel does not include the
controlled equipment.
409.110(4) Exception to (4): Short-circuit current rating
markings are not required for industrial control panels
containing only control circuit components.
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Industrial control panels
Code requirements
409.110(4)
•
SCCR marked on nameplate “plainly visible”
•
Note: UL 508A currently requires the nameplate marking
to be visible without opening the door or cover of the
enclosure.
409.22(A)
•
Do not install when SCCR is less than the available fault
current
409.22(B)
•
Determine available fault current
•
Date and documentation to AHJ
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Industrial machinery definition
NEC 670.2 Definition
Industrial Machinery (Machine). A power-driven machine
(or a group of machines working together in a coordinated
manner), not portable by hand while working, that is used
to process material by cutting; forming; pressure; electrical,
thermal, or optical techniques; lamination; or a combination
of these processes. It can include associated equipment
used to transfer material or tooling, including fixtures, to
assemble/ disassemble, to inspect or test, or to package.
[The associated electrical equipment, including the logic
controller(s) and associated software or logic together with
the machine actuators and sensors, are considered as part
of the industrial machine.]
For Machine assembly requirements see: NFPA 79
Electrical Standard for Industrial Machinery
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Industrial machinery
Code requirements
670.3(A)(4)
•
SCCR marked on nameplate and “plainly visible”
•
Note: NFPA 79 requires the nameplate to be attached to
the outside of the enclosure, or on the machine
immediately adjacent to the enclosure
670.5(1)
•
Do not install when SCCR is less than the available fault
current
670.5(2)
•
Field marked with maximum available fault current
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How much SCCR is necessary?
Equipment short-circuit current rating must be equal to or greater than the
available short-circuit current at the location where the control panel is installed.
Switchboard required to be marked/documented
with available fault current per NEC 110.24
switchboard
transformer
switchboard
panelboards
panelboards
x
x
switchboard
x
x
x
x
x
x
x
x
x
All Switchboards, Switchgear & Panelboards required to be field
marked with the available fault current per 2020 NEC 408.6
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Use utility
worst case if
available
versus
specific
transformer
= machine/equipment
location
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Setting an SCCR requirement
SCCR is based on the available fault current of each machine (use FC2).
May consider relocation of equipment and impact on SCCR.
SCCR Min:
22,000 amps
short-circuit
current: 18,450
amps
switchboard
switchboard
switchboard
panelboards
panelboards
x
x
transformer
SCCR Min:
35,000 amps
short-circuit
current: 33,302
amps
x
x
x
x
x
x
x
x
short-circuit
current: 38,499
amps
SCCR Min:
42,000 amps
x
short-circuit
current: 8,944
amps
short-circuit
short-circuit
short-circuit
short-circuit
short-circuit
short-circuit
short-circuit
current: 7,634 current: 11,093 current: 3,021 current: 19,954 current: 13,027 current: 15,732 current: 24,395
amps
amps
amps
amps
amps
amps
amps
SCCR Min:
10,000 amps
SCCR Min:
10,000 amps
x
SCCR Min:
18,000 amps
SCCR Min:
5,000 amps
SCCR Min:
22,000 amps
SCCR Min:
18,000 amps
SCCR Min:
18,000 amps
SCCR Min:
30,000 amps
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= machine/equipment
location
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Determining the equipment SCCR
1.
Short-circuit testing in high power laboratory
• Tested and listed to UL product standard
2.
Analysis methods (for device or apparatus)
• Example: UL 508A Industrial Control Panel
product standard, Supplement SB
• Or other approved method
(Engineering Method)
Paul P. Gubany Center for
High Power Technology
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Definitions
UL 508A SB
Industrial Control Panels
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Industrial control panel circuit types
UL 508A Definitions
Exception: SCCR does NOT apply to:
2.41 POWER CIRCUIT – Conductors and
components of branch and feeder circuits.
1)
2.11 CONTROL CIRCUITS – A circuit that
carries the electric signals directing the
performance of a controller, and which does not
carry the main power circuit. A control circuit is, in
most cases, limited to 15 amperes.
•
SCCR applies only to POWER CIRCUIT
devices, not CONTROL CIRCUIT devices
(SB4.1.1 and SB4.2.1)
Transformers, reactors, CT’s, drytype capacitors, resistors, varistors,
one-port SPDs and voltmeters.
2) Wye-delta “S” contactor
3) Cord & plug connected enclosure AC
4) Wiring ferrules used for internal
wiring
5) Components on the load side of a
variable speed drive.
(SB4.2.1 Exceptions)
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Industrial control panel circuit locations
UL 508A Definitions
Feeder circuits
2.3 BRANCH CIRCUIT – The conductors and
components following the last overcurrent
protective device protecting a load.
Branch circuits
2.19 FEEDER CIRCUIT – The conductors and
circuitry on the supply side of the branch circuit
overcurrent protective device.
•
1
Branch and feeder power circuits supply
external loads: motors, lighting, heating,
appliances, convenience receptacles, etc.
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Industrial control panel transformer types
UL 508A Definitions
2.42 POWER TRANSFORMER – A transformer
Power Transformer
Control Transformer
whose secondary winding supplies power to loads or a
combination of loads and control circuit devices operating
at the secondary voltage.
2.12 CONTROL TRANSFORMER – A transformer
whose secondary supplies power to control circuit devices
only (excluding loads)..
•
Power transformers feed external loads and secondary
devices supplying loads are considered in panel SCCR
•
Control transformers and secondary control devices
are not considered in panel SCCR
External
Control
Load
Circuits
Considered in SCCR
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NOT Considered in SCCR
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Example panel
SCCR also applies to
1) The branch circuit OCPD protecting
the common control circuit or the
primary of a control transformer or
power supply.
2) The OCPD protecting control
circuits supplied from the load side
of motor branch circuits.
Feeder
circuits
Branch
circuits
Exception: Secondary circuits operating
at 24 vdc maximum and supplied from a
source with a maximum output power of
100 VA, shall be considered control
circuits.
See SB3.2.1
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Slash voltage ratings
NEC Requirement
240.85 Applications. A circuit breaker with a straight
voltage rating, such as 240V or 480V, shall be permitted to
be applied in a circuit in which the nominal voltage between
any two conductors does not exceed the circuit breaker’s
voltage rating…
A circuit breaker with a slash rating, such as 120/240V or
480Y/277V, shall be permitted to be applied in a solidly
grounded circuit where the nominal voltage of any
conductor to ground does not exceed the lower of the two
values of the circuit breaker’s voltage rating and the
nominal voltage between any two conductors does not
exceed the higher value of the circuit breaker’s voltage
rating.
All fuses are straight voltage rated
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480V
480/277
Slash rating examples
277 V
C
480 V
C
480 V
480 V
A
G
B
Solidly
grounded
wye
A
G
N
277 V
480 V
C
Corner
grounded
B delta
C
480 V
480 V
A
G
High
B resistance
grounded
N wye
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A
Ungrounded
delta
B
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Nameplates for Industrial Control Panels
UL 508A Nameplate
NEC 409.110 Nameplate
1.
1.
Manufacturer’s Name
2.
Supply Voltage, # Phases, Frequency
& Full load current
Manufacturer’s Name
2.
Complete electrical per 49.1
a) Voltage Rating
b) Total FLA
c) HP/A Largest Motor
d) # Phases
e) Frequency
3.
Marked if more than one Supply
3.
Short Circuit Current Rating
4.
Short Circuit Current Rating
4.
Field wiring diagram number when
required load ratings
5.
Field wiring diagram number when
required load ratings
5.
Factory identification
6.
Enclosure Type rating
6.
Enclosure Type rating
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UL 508A Nameplates
Supply Voltage
•
49.1 The input terminals intended to be connected to each source of supply shall be
rated in volts, total full-load amperes, ampere or horsepower rating of the largest motor
(when multiple loads are controlled), number of phases when other than single phase,
and the frequency.
•
49.6 The voltage rating of an industrial control panel shall not exceed the voltage rating
of any component connected to the source of supply. When an industrial control panel
contains components marked with a slash voltage rating, such as 120/240, 480Y/277,
or 600Y/347, the voltage rating of the industrial control panel shall be:
•
a) The complete slash voltage rating, when intended for connection to the higher voltage; or
•
b) Not more than the lower voltage rating.
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Determining overall panel
SCCR
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Overview of component SCCRs
Short-circuit current ratings
Panel SCCR is based on:
Drives, soft-starters,
contactors, overloads,
disconnects,
fuseholders, busbars,
contactors, receptacles,
multi-wire lugs, power
distribution blocks, etc.
• Power circuit component SCCRs
• Overcurrent protective device
interrupting ratings
•
Includes those supplying common
control, control transformer, and
power supply
Interrupting ratings
UL Class fuses, UL 489
molded case circuit
breakers
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Per SB4.4:
Three Step Method for calculating SCCR
Per SB4.4:
1. OCPD Interrupting Rating
2. Component SCCR with OCPD
protection
3. Increasing Branch circuit SCCR with
C.L. Feeder device
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Step #1
Determine SCCR of each branch circuit
Per SB4.4:
1. Identify OCPD interrupting rating
a) Identify the lowest OCPD I.R. in the
feeders and branch circuits.
1
b) The panel can not have a SCCR
higher than the lowest OCPD I.R.
What is the SCCR Goal???
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Step #2
Determine SCCR of each branch circuit
Per SB4.4:
2. Determine the SCCR of each
Component with its associated
OCPD in the branch circuit.
a) Identify component SCCRs of each
branch circuit device (SB4.2.2)
1
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Step #2
SCCR of individual power circuit components
UL 508A Requirement
SB4.2.2 The short circuit current rating of a feeder or branch circuit
component shall be established by one of the following methods:
a) The short circuit current rating marked on the component or on
instructions provided with the component;
1
b) The short circuit current rating determined by the voltage rating of
the component and the assumed short circuit current from Table
SB4.1; or
c) The short circuit current rating for a component that has been
investigated in accordance with the performance requirements,
including short circuit test requirements for standard fault currents
or high fault currents specified in the associated product standard,
and described in the manufacturer’s Procedure.
Technical Literature, White Papers,
Catalogs, Manufacturer Website –
INFORMATION ONLY!
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Step #2
Component short-circuit current ratings
SB4.2.2 a)
All components tested with an upstream
OCPD to obtain compliant SCCR
SCCR details:
• Component SCCR value
• Upstream OCPD type and size
• Other conditions
• Standard or High Fault SCCR
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Step #2
Component SCCR – standard fault
SB4.2.2 b)
UL 508A Table SB4.1
• Minimum rating for component
when tested with OCPD
• Found on product label,
instruction sheet or UL website
• Default rating in Table SB4.1
can be used if unknown
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Step #2
Component SCCR – high fault
SB4.2.2 c)
Cautionary marking required per SB5.2
• Optional higher rating
• Specifies maximum amp rating of
OCPD
• Found on product label or
instruction sheet (not UL website)
WARNING: Risk of Fire or Electric Shock – The
opening of the branch-circuit protective device may
be an indication that a fault current has been
interrupted. All current-carrying parts and other
components protected by this device should be
examined and replaced if damaged. If burnout of a
current element of an overload relay occurs, the
complete overload relay must be replaced.
• Must mark panel (component)
accordingly
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Step #2
Component SCCR – high fault examples
PDB in the Feeder Circuit
must be Listed to
UL1953
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Step #2
SCCR of individual power circuit components
UL 508A Requirement
SB4.2.3 A high fault short circuit current rating for a feeder
or branch circuit component, as specified in SB4.2.2 (a) or
(c), shall only be used as the short circuit current rating of
the component when the specified branch circuit protective
device is provided.
Replace RK5
with RK1
Exception No. 1:
•
•
A fuse with equal to or less than peak letthru current can be substituted for the fuse
specified in the SCCR
Replace RK1
with J
Equal or Better
See Table SB4.2 for peak let-through of
fuses
Replace J with Class
CF CUBEFuse
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Step #2
SCCR of individual power circuit components
UL 508A Requirement
SB4.2.3 A high fault short circuit current rating for a feeder
or branch circuit component, as specified in SB4.2.2 (a) or
(c), shall only be used as the short circuit current rating of
the component when the specified branch circuit protective
device is provided.
Exception No. 2:
•
If the panel is marked according to
SB5.1.2, the specified branch circuit
protection can be provided in the field.
Can be provided in the field if
marked according to SB5.1.2
ABC Company
Machine XYZ
Serial No: 1234567
123 Main St, City, ST 01234
Model: XZY123
480/277
Max HP
Volts
Phase
50
3
FLA
Frequency 60Hz
SCCR SYM: 65kA WHEN FED
BY 200 AMP CLASS J FUSE..
124
UL
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Step #2
SCCR of individual power circuit components
UL 508A Requirement
SB4.2.3 A high fault short circuit current rating for a feeder
or branch circuit component, as specified in SB4.2.2 (a) or
(c), shall only be used as the short circuit current rating of
the component when the specified branch circuit protective
device is provided.
Equal or Better
1
1
Exception No. 3:
•
•
A listed current-limiting breaker with equal to or less
than peak let-thru and I2t can be substituted for the
specified breaker per the SCCR, provided the
specified breaker is current-limiting.
Can be replaced if both marked
current-limiting and equal to or
better performance
See circuit breaker manufacturer let-through charts
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Step #2
SCCR of individual power circuit components
UL 508A Requirement
SB4.2.3 A high fault short circuit current rating for a feeder
or branch circuit component, as specified in SB4.2.2 (a) or
(c), shall only be used as the short circuit current rating of
the component when the specified branch circuit protective
device is provided.
Exception No. 4:
•
A current limiting fuse is permitted to be
substituted for a non-current limiting OCPD
provided the interrupting rating is equal to
or greater and the ampacity is equal to or
less than the specified overcurrent
protective device.
Allows current-limiting fuse to
replace non-current limiting OCPD
Previously was any currentlimiting overcurrent device now
only current limiting fuse.
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Step #2
NEW - High fault SCCR for bus bar
UL 508A Requirement
NEW
• Bus bar systems
SB4.2.4 A high fault short circuit current rating of a bus bar
can additionally be determined by one of the
following methods:
a) Use of a bus bar system, that complies with the
Standard for Industrial Control Equipment, UL508, with
the short circuit current rating marked on the component
or on instructions provided with the component and
installed according to the installation instructions
provided by the product; or
• Construction method
based on Appendix D
b) Use of a bus bar system constructed with electrical
ratings and short circuit current rating in accordance
with Appendix D.
• For custom bus bar
configurations
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Step #3
Determine SCCR of each branch circuit
Current-limiting fuse
Per SB4.4:
3. Determine if the Branch component
SCCR can be raised using the
Current Limiting OCPD in the
feeder.
1
a) Determine if branch component SCCR
can be raised using a current limiting
OCPD in the feeder circuit (SB4.3)
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Step #3
Raise branch SCCR using current-limitation
Methods to raise branch SCCR utilizing
upstream components in the feeder (SB4.3)
1. Power transformer (SB4.3.1)
Feeder circuits
Branch circuits
2. Current-limiting circuit breaker (SB4.3.2)
3. Current-limiting fuse (SB4.3.3)
1
4. Current-limiting breaker or currentlimiting fuse supplied in the field when
the panel is marked per SB5.1.3
(SB4.3.4)
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Step #3
Circuits supplied by power transformer
Per SB4.3.1:
For circuits supplied by power transformer with isolated
secondary, SCCR shall be one of the following:
a) The interrupting rating of the primary side OCPD if the
component SCCR’s or interrupting ratings are greater than or
equal to the secondary short circuit current calculated or
defined in Table SB4.3 or SB4.4.
b) The lowest SCCR or interrupting rating of the downstream
devices if the secondary short-circuit current is greater than
any of the downstream component SCCRs or interrupting
ratings
Primary
OCPD IR
Feeder
Short-circuit
current
Branch
IR
Branch
Component
SCCR
Branch
Applies to feeder and branch circuits
External
Load
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Step #3
Circuits supplied by power transformer example
•
Single phase 3 kVA XFMR with 120 V secondary
•
Maximum secondary short-circuit current = 1,200A
•
Downstream OCPD IR/Component SCCR = 10 kA/5 kA
•
Primary side OCPD IR = 200 kA
•
SCCR = 200 kA (primary OCPD IR) since 1.2 kA < 5 kA
200 kA
IR:
200 kA
Short-circuit
current = 1.2 kA
IR:
10 kA
Table SB4.3
Single phase transformer secondary available short circuit currents (Amps)
SCCR:
5 kA
External
Load
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Step #3
Current-limiting fuse in the feeder 200A
Per SB4.3.3:
For branch circuits supplied by a Class CC, G, J, L,
RK1, RK5, or T, SCCR shall be determined by:
1.
Feeder IR
Determine the peak let-through current at a selected
available short-circuit current from Table SB4.2
2. If peak let-through current is less than the component SCCR,
adjust the component SCCR to the selected available shortcircuit current
Feeder
Let-thru
current @
short-circuit
current
Branch
IR
3. Compare adjusted component SCCR to branch IR/SCCR –
the lower value is the branch circuit SCCR.
Branch
1
Component
SCCR
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Branch
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Step #3
UL508A Table SB4.2
•
Identifies peak let-through
current and I2t let-through at
50kA, 100kA and 200kA
•
Can not use manufacturer’s
published data or Irms letthrough per UL 508A.
Excerpt from Table SB4.2
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Step #3
Current-limiting fuse in the feeder 200A
IR:
14 kA
14 kA
1
Fuse
Fuse
Let-thru
30 kA
@200kA
Fuse
Fuse
Let-thru
20 kA
@100kA
Excerpt from Table SB4.2
Scenario 2
IR:
300 kA
Fuse
IR:
300 kA
Fuse
Scenario 1
200 kA
IR:
200 kA
100 kA
SCCR:
SCCR:
100 kA
SCCR:
22 kA
(w/Class
CC/J fuse)
22 kA
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Ip at 200kA = 30kA
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Step #3
Current-limiting feeder device supplied in the field
Marking:
•
Type and size of
feeder protection
required
Machine XYZ
ABC Company
Serial No: 1234567
SCCR: 100 kA rms sym.
Model: XZY123
when fedPhase
by 3max 200
A
Frequency
Volts 480/277
60Hz
MaxClass
HP
FLA
1245
J50fuse otherwise
SCCR SYM: 65kA WHEN FED BY
200kA
AMP CLASS J FUSE..
Fuse
Fuse
SB4.3.4 The specified circuit breaker marked “current
limiting” or current-limiting Class of fuse supplied in the
feeder circuit that limits the peak let-through current
available in accordance with SB4.3.2 and SB4.3.3 is able
to be provided in the field when the panel is marked in
accordance with SB5.1.3.
Fuse
UL 508A Requirement
Can be provided in the field if
marked according to SB5.1.3
123 Main St, City, ST 01234
UL
Example label
Benefits:
1) Reduces enclosure size
and cost
2) Eliminates exposure to
live parts in panel
3) Upstream overcurrent
device can be used for
arc flash protection
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Next Gen CCP2 – Class CF CCP
Finger safe
Lockout/tagout
IP20 finger safe with 10 AWG or
larger wire
Padlockable handle accepts standard ¼”
lock or hasp lock
Lug options
Handle mechanism
Available with single box lug with
expanded wire torque ratings & multiwire accessory
Accepts the addition of a rotary or
flange through the door operator
Compact size
Fuse indication
20% less footprint than MCCB and 2/3 of
the size of a standard fusible switch
For both AC and DC voltages
Switch interlock
Fuse rejection
Built-in switch interlock prevents
removing the fuse under load
Ampacity rejecting CUBEFuse rating
greater than the switch rating
Note: Blue indicates new features from previous version
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CCP size comparison
Fuse indication
Local open fuse indication for both AC and DC
Lockout/tagout
¼” LOTO on handle mechanism
Fuse interlock
Built-in fuse interlock helps prevent
removing fuse under load
200A fuse switch
30A Class CC fuse switch
100A fuse switch
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Compact Circuit Protector handle
mechanism
Rotary
Features
Flange
Firm snapping action
Distinct feel for confidence of
ON/OFF status
Compact
No footprint impact; allows
user to maintain compact size
CABLE
Easy access to fuses
Speeds fuse replacement
Easy mounting
connection
Four screws secure mechanism
UL listed
UL Recognized accessory
ROD
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Identify OCPD interrupting ratings
Per SB4.4:
1. Identify the interrupting rating for
each overcurrent protective device.
2. Determine the SCCR of each
branch circuit & Feeder component.
1
3. Increase the Branch Component
with a C.L. Feeder OCPD
4. The panel SCCR is the lowest value
from steps 1-3.
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Determine SCCR of the branch & feeder components
Per SB4.4:
1. Identify the interrupting rating for
each overcurrent protective device.
2. Determine the SCCR of each
branch circuit & Feeder component.
1
3. Increase the Branch Component
with a C.L. Feeder OCPD
4. The panel SCCR is the lowest value
from steps 1-3.
© 2020 Eaton. All rights reserved..
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Increase Branch component using C.L. in Feeder
Per SB4.4:
Current-limiting fuse
1. Identify the interrupting rating for
each overcurrent protective device.
2. Determine the SCCR of each
branch circuit & Feeder component.
1
3. Increase the Branch Component
with a C.L. Feeder OCPD
4. The panel SCCR is the lowest value
from steps 1-3.
© 2020 Eaton. All rights reserved..
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Determine overall panel SCCR
Per SB4.4:
Current-limiting fuse
1. Identify the interrupting rating for
each overcurrent protective device.
2. Determine the SCCR of each
branch circuit & Feeder component.
1
3. Increase the Branch Component
with a C.L. Feeder OCPD
4. The panel SCCR is the lowest value
from steps 1-3.
© 2020 Eaton. All rights reserved..
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Examples and practice
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www.menti.com Code: 36 79 81 8
Practice 1 – What is the panel SCCR?
G
1
A
1
E
1
C
D
F
B
A
100 A Circuit Breaker
IR = 35 kA at 480V
B
Power Distribution Block
Default SCCR = 10 kA
C
15 A Class CC Fuse & Holder
IR = 200 kA at 600V
SCCR (Holder) = 200 kA
D
10 HP Drive
SCCR = 100 kA at 480V
with 15 A or less Class CC Fuse
E
15 A Breaker
IR = 14 kA at 480V
F
20 A Contactor
SCCR = 25 kA at 480V
with 30 A or less breaker
G
6 A Miniature Breaker
IR = 10 kA at 480/277V
© 2020 Eaton. All rights reserved..
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www.menti.com Code: 36 79 81 8
Practice 1 – What is the panel SCCR?
The panel SCCR is:
10 kA
10 kA
480/277
351kA
1 14 kA 1
200 kA
100 kA
10 kA
Step #1 – OCPD IR
10kA
Step #2 – Component
SCCR w/ OCPD
10kA
25 kA
Step #3 – C.L. Feeder
OCPD increasing
Branch component
© 2020 Eaton. All rights reserved..
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www.menti.com Code: 36 79 81 8
Practice 2 – What is the panel SCCR?
G
1
A
1
E
F
1
C
D
B
© 2020 Eaton. All rights reserved..
A
100 A Eaton EGH Circuit Breaker
IR = 65 kA at 480V
B
Power Distribution Block
SCCR = 65 kA at 480V with max 125 A
EGH (#10 AWG or larger wire)
C
15 A Class CC Fuse & Holder
IR = 200 kA at 600V
SCCR (Holder) = 200 kA
D
10 HP Drive
SCCR = 100 kA at 480V
with 15 A or less Class CC Fuse
E
15 A Breaker
IR = 14 kA at 480V
F
20 A Contactor
SCCR = 25 kA at 480V
with 30 A or less breaker
G
6 A Class CC Fuse & Holder
IR = 200 kA at 600V
SCCR (Holder) = 200 kA
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www.menti.com Code: 36 79 81 8
Practice 2 – What is the panel SCCR?
The panel SCCR is:
200 kA
14 kA
480V
651kA
1 14 kA 1
200 kA
100 kA
65 kA
Step #1 – OCPD IR
14kA
Step #2 – Component
SCCR w/ OCPD
25kA
25 kA
Step #3 – C.L. Feeder
OCPD increasing
Branch component
© 2020 Eaton. All rights reserved..
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www.menti.com Code: 36 79 81 8
Practice 3 – What is the panel SCCR?
G
A
E
F
C
D
B
A
100 A CUBEFuse and CCP2
IR = 300 kA, SCCR = 200 kA
Ip let-through = 14kA at fault of 200kA
B
Power Distribution Block
SCCR = 200 kA at 600V with max 200A
Class J fuse (#12 AWG or larger wire)
C
15 A CC Fuse & Holder
IR = 200 kA
SCCR (Holder) = 200 kA
D
10 HP Drive
SCCR = 100kA at 480V
with 15 A Class CC Fuse
E
15 A CUBEFuse and CCP2
IR = 300kA, SCCR = 200 kA
F
20 A Contactor
SCCR = 100 kA at 480V with 20 A
max Class J fuse (Class CF or CC)
G
6 A Class CC Fuse & Holder
IR = 200 kA at 600V
SCCR (Holder) = 200 kA
© 2020 Eaton. All rights reserved..
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www.menti.com Code: 36 79 81 8
Practice 3 – What is the panel SCCR?
The panel SCCR is:
200 kA
300 kA
300 kA
200 kA
100 kA
200
200 kA
200 kA
480V
Step #1 – OCPD IR
200kA
Step #2 – Component
SCCR w/ OCPD
100kA
Step #3 – C.L. Feeder
OCPD increasing
Branch component
200kA
200
100 kA
© 2020 Eaton. All rights reserved..
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Keys to achieve high assembly SCCR
• Branch and feeder circuit OCPD
with high interrupting rating
• Branch and feeder components
with high fault SCCR
• Increase branch circuit
component SCCR using currentlimiting feeder OCPD’s or
transformer rules
© 2020 Eaton. All rights reserved..
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Compliance is easy
• Design and proposal
• Ask for customer SCCR requirements
• Determine a standard SCCR level – 65 kA possibly
• Review and analysis
• Look for the lowest rated SCCR or interrupting rating
• Utilize high fault SCCR components and current limiting
OCPDs for the highest SCCR
© 2020 Eaton. All rights reserved..
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Additional resources and tools
•
2017 SCCR Code changes booklet
•
Fault current calculator – FC2
•
Fuseology Handbook
•
SPD – Electrical Protection Handbook
•
SCCR Protection Suite
•
SCCR and IR checklist
•
Available in the app store or play store
© 2020 Eaton. All rights reserved..
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Questions?
Joe Pavia, P.E.
Field Application Engineer
JoemPavia@Eaton.com
317-665-1956
© 2018 Eaton. All rights reserved..
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