Grounding FTTH Systems at the Home. May 8 , 2012 Presented by: Dean L. Mischke, P.E. Finley Engineering Company, Inc . Disclaimer. The following presentation is the opinion of Dean Mischke and has not been verified with NFPA or IEEE . Reference Materials.
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May 8, 2012
Dean L. Mischke, P.E.
Finley Engineering Company, Inc.
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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
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
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.
The point of entrance is defined in 770.2 as the emergence through:
a. Grounding Conductor. The grounding conductor shall be 800.100(A)
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
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.
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
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
(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).
(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.
Clamps designed to clamp on the outside of the meter box may be not approved in your area.
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.
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.
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.
1. “Communication Ground Do Not Remove”
2. Company Name
3. Trouble Report Telephone Number
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Dean L. Mischke, P.E., V.P.