Grounding FTTH Systems at the
Home
May 8, 2012
Presented by:
Dean L. Mischke, P.E.
Finley Engineering Company, Inc
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Disclaimer
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The following presentation is the opinion of Dean Mischke
and has not been verified with NFPA or IEEE.
Reference Materials
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2012 National Electric Safety Code (C2-2012 NESC)
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Administered by IEEE
Approved by American National Standards Institute (ANSI)
Covers Distribution Network
New Edition every 5 years (next one due 2017)
http://standards.ieee.org/about/nesc/
Reference Materials
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2011 National Electric Code (NEC)
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Administrated by National Fire Protection Agency (NFPA)
Covers Premise Wiring
New Edition every 3 years
Read the 2011 NEC online at:
http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=70
View the document online (read only)
View the 2011 edition online
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Reference Materials
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RUS 1751F-802 Electrical Protection Grounding Fundamentals
(1994)
RUS 1751F-805 Electrical Protection at Customer Locations
RUS 1751F-815 Electrical Protection of Outside Plant
Purpose of Grounding and Bonding
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Primary function of grounding and bonding is the
protection of the customer and maintenance personnel from
lightning, induced voltages, or direct contact with electrical
supply circuits.
Secondary Function of grounding and bonding is to reduce
the amount of damage the communication facilities from
lightning, induced voltages, or direct contact with electrical
supply circuits.
Finally, to comply with NEC and NESC.
OSP Grounding & Bonding Issues: NESC
Section 2 Definitions
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Effective ground/effectively grounded: Bonded to an effectively
grounded neutral conductor or to a grounding system designed to
minimize hazard to personnel and having resistance to ground low
enough to permit prompt operation of circuit protection devices.
Restricted Access: Where exclusive control is maintained.
OSP Grounding & Bonding Issues: NESC
Section 9 Grounding methods for electrical supply
and communications facilities
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Rule 099 Additional Requirements for Communications
Apparatus
B. The Communications grounding conductor shall not be less than
#6 AWG; however, owner preference may be larger
C. Bonds between communication ground rods and electrical supply
neutral rods shall not be required to be greater than #6 AWG
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Important Sections of National Electric Code (NEC)
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Article 90 Introduction
Article 100 Definitions
Article 250 Grounding and Bonding
Article 480 Storage Batteries
Article 770 Optical Fiber Cables and Raceways
Article 800 Communications Circuits
Article 820 Community Antenna Television and Radio Distribution
Systems
Article 830 Network-Powered Broadband Communications Systems
Article 840 Premise-Powered Broadband Communications Systems
Bonding Conductor Term Change in NEC
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The term Grounding Conductor has been replaced by Bonding
Conductor or Grounding Electrode Conductor where
applicable
Bonding Conductor Term Change in NEC
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Bonding Conductor Term Change in NEC
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Copper Communication Circuits within Buildings
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Copper Communication Circuits are defined as low voltage
communication circuits including voice, audio, video, data,
interactive services, alarm, etc.
The rules governing copper communications circuits are
dependant on how the service is derived:
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If the service is derived from another building, Article 800
If the service is derived from a Network Powered fiber-fed device,
Article 830
If the service is derived from a Premise Powered fiber-fed device,
Article 840
NEC Article 830
Network Powered Broadband Systems
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Article 830 covers Coaxial Cable powered broadband systems,
composite coaxial and twisted pair, or composite fiber with
conductors with power.
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In summary all of the previous rules apply for metallic cable entering
the building
Services voice/data and video must comply with rules in Articles
770, 800, and 820
Introduces the Network Interface Unit (NIU) as the device that
derives the component voice, data, and video signals at the premise.
Power Limitations are specified in 830.15(1) and (2) and Table
830.15 (see next slide)
Medium power systems entering the building shall use Type BMU,
BM, or BMR Cable 830.40(A)
Low power systems entering the building shall uses Type BLU or
BLX cables or approves substitutions in Table 830.154(b) 830.40(B)
NEC Article 830
Network Powered Broadband Systems
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NEC Article 830
Network Powered Broadband Systems
1Vmax, Imax, and VAmax are determined with the current-limiting impedance
in the circuit (not bypassed) as follows:
Vmax—Maximum system voltage regardless of load with rated input
applied.
Imax—Maximum system current under any noncapacitive load, including
short circuit, and with overcurrent protection bypassed if
used. Imax limits apply after 1 minute of operation.
VAmax—Maximum volt-ampere output after 1 minute of operation
regardless of load and overcurrent protection bypassed if used.
2Overcurrent protection is not required where the current-limiting device
provides equivalent current limitation and the current-limiting
device does not reset until power or the load is removed.
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NEC Article 840
Premise Powered Broadband Systems
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Article 840 is new for 2011 and covers premise-powered
optical fiber broadband systems that provides any
combination of voice, video, data, and interactive services
through an ONT.
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The Article becomes the starting point for
communications circuits derived from premise-powered,
fiber-fed ONTs.
Introduces the Optical Network Terminal (ONT) as the device
that derives the component voice, data, and video signals at
the premise.
NEC Article 840
Premise Powered Broadband Systems
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Article 840: Definition of exterior or interior rated ONT
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All exterior ONTs are required to be grounded/bonded as per
the requirements of their UL listing
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Interior ONTs typically do not require to be
grounded/bonded per the requirements of their UL listing
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This applies regardless if the ONT is installed indoors or
outdoors
I am not aware of any indoor ONTs that can be installed
outdoors
NEC Article 840
Premise Powered Broadband Systems
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Article 840.100 ONT and Fiber Cable Grounding
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Services voice/data and video must comply with rules in Articles
770.100 for the fiber, 800.100 for the copper communications cables,
and 820.100 for the coaxial cables
NEC Article 770
Fiber Optic Cable within Buildings
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Article 770 Scope: Applies to the installation of fiber optical
cable, raceways, and optical cable assemblies
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Conductive Fiber Optic Cable: A factory assembly under an overall
covering comprised with non-metallic and metallic non-current carrying
members (metallic sheath or strength members) 770.2
Non-Conductive Fiber Optic Cable: A factory assembly under an overall
covering that is comprised entirely of non-conductive members 770.2
Composite cables (copper conductors under the same sheath of optical
fibers) shall be classified in accordance of the type of electrical
conductors 770.3(B)
NEC Article 770
Fiber Optic Cable within Buildings
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Article 770.48 Unlisted Cables Entering Buildings
– Conductive and Non-Conductive fiber optic cable may be
installed in building spaces other than risers, ducts used for
environmental air, plenum used for environmental air (some
building code inspectors include in this definition any
suspended ceiling with ducted air) must terminate within 50’
from the point of entry 770.48(A)
The point of entrance is defined in 770.2 as the emergence through:
 Exterior wall
 Concrete floor slab
 Rigid Metal Conduit (must run to exterior wall)
 Intermediate Metal Conduit (must run to exterior wall)
NEC Article 770
Fiber Optic Cable within Buildings
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Article 770.48 Unlisted Cables Entering Buildings
– Unlisted Non-Conductive fiber optic cable may be installed
in raceway as long as the raceway complies with
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Article 342 Intermediate Metallic Conduit, Type IMC
Article 344 Rigid Metal Conduit, Type RMC
Article 352 Rigid Polyvinyl Chloride Conduit, Type PVC
Article 358 Electrical Metallic Tubing, Type EMT
NEC Article 770
Fiber Optic Cable within Buildings
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Article 770.93 Grounding or Interruption of Non-Current
Carrying Metallic Members of Fiber Optic Cable
– Entering Buildings: Cable exposed to contact with electric
light or power conductors shall be either grounded as
specified in Article 770.100 or interrupted by an insulating
joint as soon as possible at the point of entry. 770.93(A)
– Terminating On The Outside of a Building: Cable exposed to
contact with electric light or power conductors shall be
either grounded as specified in Article 770.100 or
interrupted by an insulating joint as soon as possible at the
point of termination. 770.93(B)
NEC Article 770
Fiber Optic Cable within Buildings
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Article 770.100 Grounding of Non-Current Carrying Metallic
Members of Fiber Optic Cable
– Bonding Conductor or Electrode Grounding Conductor
shall be
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listed and shall be either insulated covered, or bare 770.100(A)(1)
Minimum size of 14 AWG and shall not be required to be larger than
#6 AWG (Note the 2012 NESC calls for a # 6 AWG in all cases,
given the conflict, it will be best to standardize on the # 6)
Run in a straight line
Must be done in accordance to Article 250
Protected from damage
See Bonding and Grounding in Article 800
NEC Article 800
Copper Cable within Buildings
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Article 800.100 Cable and Primary Protector Grounding. The
metallic member(s) of the cable sheath, were required by Section
800-93, and primary protectors shall be grounded as specified in (a)
though (d)
a. Grounding Conductor. The grounding conductor shall be 800.100(A)
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1. Listed and insulated, covered, or bare
2. Copper or other corrosion-resistant conductor, solid or stranded.
3. Size shall not be less that the current carrying capacity of the sheath or
current carrying conductors but not less than 14 AWG and shall not be
required to exceed #6 AWG (Note the 2012 NESC will call for a # 6
in all cases. In addition, RUS also calls for an insulated #6))
4. Length of less than 20 feet. Runs greater than 20 feet require a ground
rod as identified in 800.100(B)(2) and bonded to the service entrance
ground rod with a #6 conductor as specified in 800.100(D).
5. Run in a straight line.
6. Protected from damage
NEC Article 800
Copper Cable within Buildings
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Article 800.100 Continued
b. Electrode. The grounding electrode shall be connected as
follows 800.100(B)
1. To the nearest accessible location on the following:
a. The building structural grounding electrode system as covered in
Section 250.50
b. The power service accessible means external to enclosures as
covered in Section 250.94 Exception
c. Metallic service raceway
e. The service equipment enclosure
f. The grounding electrode conductor or the grounding electrode
conductor metal enclosure of the power system
g. To the grounding conductor or the grounding electrode of a
building or structure disconnecting means that is grounded to an
electrode as covered in Section 250.32.
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NEC Article 800
Copper Cable within Buildings
Article 800.100 Continued
C. Electrode Connection. Connections to grounding electrodes shall comply
with Section 250.70
D. Bonding of Electrodes. A bonding jumper not smaller than # 6AWG
shall be connected between the communications grounding electrode and
power grounding electrode system.
Exception for Mobile Homes see 800.106
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NEC Article 800
How Many Ground Rods??
800.100(A)(4) sets maximum length to 20’
The Exception allows for a communications
ground rod, then bonding as specified in
800.100(D)
800.100(D) in essence states that you must
bond with a #6 AWG with no reference for
additional ground rods
Grounding
Conductor
Grounding
Conductor
100’
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Bonding
Conductor
NEC Article 800 Reference to Article 250.70
Copper Cable within Buildings
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Article 250.70 Methods of Grounding Conductor Connection to
Electrodes: The grounding conductor shall be connected to the
grounding electrode by
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exothermic welding
listed lugs, pressure connectors, clamps, or other listed means.
Connections depending on solder shall not be used.
Grounding clamps shall be listed for the materials in the grounding
electrode and grounding electrode.
Clamps in contact with the soil shall be rated for direct burial.
No more than 1 conductor per clamp unless the clamp is listed for
more conductors.
NEC Article 820
Coax Cable within Buildings
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Article 820 covers Coaxial Cable providing a CATV type
service wiring within the building.
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In summary all of the previous rules apply for shielded cable
entering the building
Coaxial cable must have a primary protector and be grounded
and bonded as described in the pervious sections if the cable is
attached to the outside of the building or leaves the building
820.93
New for 2011, for coaxial cable that does not leave the
building, Article 820.100 Exception allows the cable to be
grounded from the equipment; however, the equipment must
be grounded to a grounded receptacle that has a dedicated
grounding conductor. A cord and plug is not acceptable. The
net result of this code is that none of the ONTs are
provisioned to accept this kind of ground so a coaxial
ground is still required.
NEC Article 840
Premise Powered Broadband Systems
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Article 840.101 Premise Circuits Not Leaving the Building: Where
the ONT is served by a nonconductive fiber optic cable or where
the metallic non-current carrying elements are interrupted by an
insulating joint or equivalent device, and the ONT and it’s circuits
are entirely contained within the building.
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Almost impossible to assure that wiring will always
remain in building
Is wiring under vinyl siding still contained within the
building?
NEC Article 840
Premise Powered Broadband Systems
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Article 840.101 Premise Circuits Not Leaving the Building:
Continued
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Communication Circuit Grounding is not required 840.101(B)
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If the communication circuit goes to the outside of the building,
then Article 840.90, which references Article 800.90 will apply.
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If the circuit stays under the requirements in Article 800.90
Informational Notes (1-3), then the circuit does not need primary
protection
NEC Article 840
Premise Powered Broadband Systems
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Article 840.101 Premise Circuits Not Leaving the Building:
Continued
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ONT Grounding: The ONT is not required to be grounded
unless required as part of it’s UL listing. If the coaxial cable is
used and it is grounded as described in 840.101(A)(1) or
840.101(A)(2), the ONT can be connected with a plug and
cord 840.101(C)
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Where required to be grounded and the ONT is grounded to a
receptacle, the size of the grounding conductor is specified in
specified in 250.122
NEC Article 840
Copper Cable within Buildings
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Article 840.106 Primary Protector Grounding and Bonding at
Mobile Homes
(A) Grounding:
(1) If there is no electrical service entrance located within 30 ft. of the
exterior wall of the mobile home it serves, the ONT, if required to
be grounded, shall be connected to a grounding electrode
conductor or grounding electrode in accordance with 840.100
(2) Where there is no mobile home disconnecting means grounded in
accordance with 250.32 and located within 30 ft. of the exterior
wall of the mobile home it serves, the ONT, if required to be
grounded, shall be connected to a grounding electrode in
accordance with 800.100(B)(3).
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NEC Article 840
Copper Cable within Buildings
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Article 840.106 Primary Protector Grounding and Bonding at
Mobile Homes
(B) The ONT grounding terminal or grounding electrode shall be
connected to the metal frame or available grounding terminal of the
mobile home with a copper conductor not smaller than # 6 AWG
under any of the following conditions.
(1) Where there is no mobile home service disconnecting means as in
840.106(A)
(2) When the mobile home is supplied by a cord and plug.
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Ground Clamps
Clamps designed to clamp on
the outside of the meter box
may be not approved in your
area.
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Ground Clamps
Clamp designed to Screw on
to the Front Cover of a
Service Entrance Box. It is
UL Listed
I recommend that you do not
allow this clamp. The notes for
NEC 800.100(B)(2)
specifically state that the
bonding device is not allowed
to connect to any removable
part and cannot be installed
on the door or cover, even if it
is not removable.
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Customer Premise Grounding & Bonding Issues:
General Recommendations
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Make all attempts to ground the communication system with a
insulated #6 AWG conductor in order of preference as follows:
1.
Clamp to the service entrance grounding electrode conductor or ground
rod. Note: You cannot cut the service grounding conductor to
install your ground!!
2. Clamp to the metal aerial or buried electrical service entrance mast.
Clean contact points down to bare metal to insure a good ground.
Repaint if required after the clamp is in place.
3. Clamp to the service entrance box inside the premise.
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Customer Premise Grounding & Bonding Issues:
General Recommendations
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Do Not use the following:
1. Exposed Conduit or copper water pipe: With the increasing use of plastic in the electrical and
plumbing industry, neither grounding point can provide a reliable ground reference. While
the ground may work today, there is no assurance that plastic will not be used in the future
breaking the communication ground path.
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Always place a permanent tag at the point connection with the electrical ground. The
tag should contain the following:
1. “Communication Ground Do Not Remove”
2. Company Name
3. Trouble Report Telephone Number
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Bond the sheath at the pedestal and customer premise
For Off-Premise Extensions, bond the sheath at the initial protector. Isolate the
sheath at the outbuilding. The protector should be grounded to the electrical service
of the out building.
OSP Grounding & Bonding Issues:
Recommendations for Fiber Optic Dielectric Cable
or Dielectric Cable with a 26 AWG Trace Wire
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Background: RUS will publish their rules for grounding and bonding a
26 AWG trace wire in 2012. While the rules are not formal, they most
likely will read in essence: “As per the requirement of the Engineer and
in accordance with the NECS and NEC.”
The NESC does not address the trace wire directly. By general
description, a trace wire is considered a current carrying conductor.
The plant side of a drop falls under the NESC.
OSP Grounding & Bonding Issues:
Recommendations for Fiber Optic Dielectric Cable or
Dielectric Cable with a 26 AWG Trace Wire
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Dielectric OSP cable does not have to be grounded.
Per 770.93, you can isolate the trace wire instead of grounding
Dielectric OSP cable with 26 AWG Trace Wire should be grounded as
follows:
– Only one end of the trace wire should be grounded.
– If both ends are grounded, it is a certainty that the trace wire will be
destroyed due to lightening and it will be impossible to locate the
cable.
– The Owner/Engineer should designate which pedestal the one end
of the trace wire will be grounded (all even pedestals will be
grounded, etc.)
ONT Grounding Matrix
ONT Location Matrix
1/26/2012
Preference
1
Demarcation Location
Outdoor
ONT Type
Indoor
ONT Location
Indoor
2
Indoor
Indoor
Indoor
3
4
None
Outdoor
Outdoor
Outdoor
Outdoor
Indoor
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None
Outdoor
Indoor
Drop Type
Flat drop
Armored
Flat drop
Armored
All
Flat drop
Armored
All
Notes:
1: Outdoor cable can extend no more than 50' inside the building (Wall penetration, exit metallic
conduit, or exit through concrete floor slab).
2: Armored drop cable needs to be grounded in all cases due to lightning risk.
3: When in doubt, ask.
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Grounding Method Allowed
Isolate or ONTB2-5
ONTB2--5
Isolate or ONTB2-5
ONTB2—5
ONTB2—5
ONTB2—5
ONTB2—5
ONTB2--5
ONTB2
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ONTB3
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ONTB4
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ONTB5
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ONTB6
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ONTB7
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ONTB8
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Thank you
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Dean L. Mischke, P.E., V.P.
d.mischke@fecinc.com
715-930-7255