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#101975 - 05/06/04 10:26 AM grding of teck feeders

Registered: 10/22/03
Posts: 178
Loc: toronto canada
If i am running a set of feeders in teck do i have to run a grd wire along side or is the inner sheathing enough.

2014 / 2011 NEC & Related Books and Study Guides
#101976 - 05/06/04 04:16 PM Re: grding of teck feeders
crash Offline

Registered: 10/21/03
Posts: 130
Loc: Calgary Canada
Getelectric: It sounds to me like you are using single conductor Teck cable. If that is the case, then only one end of the Teck cable is to have its sheath bonded to ground. Check out 4-008 (1),(c), and read the material in appendix B. If only one end of the sheath is bonded to ground then it cannot be used as a bonding condutor. Bonding both ends of the cable would require you to comply with 4-008(1),(a).

I do not think that 10-804(g) and 10-510(2) apply, as the cable is of a construction that does not incorporate a bonding conductor.

[This message has been edited by crash (edited 05-06-2004).]

[This message has been edited by crash (edited 05-06-2004).]

#101977 - 05/07/04 05:01 AM Re: grding of teck feeders

Registered: 10/22/03
Posts: 178
Loc: toronto canada
Crash you are right it is single conductor,but my question is do i have to run a separate ground wire with a teck run.( 4 250mcm tecks plus a grd or just 4 250 tecks).

#101978 - 05/07/04 02:50 PM Re: grding of teck feeders
Tony Moscioni Offline

Registered: 05/15/01
Posts: 144
Let me explain the application of Rule 4-008 to situations where the total circuit ampacity exceeds 400 A but each individual cable carries less than 425 A.

If the ampacity of each current carrying conductor is less than 425a per phase, then you can have 1/4" aluminum plates on each end
without the use of a bonding conductor installed between the run.

For example, a 1200 A feeder is installed in free air using three single conductor cables per phase.

Can aluminum plates be used at both ends of the feeder?

Answer: Yes


Each conductor (cable) in the above circuit will carry approximately 400 A when installed in accordance with Rule 12-108 and the Appendix B note to the rule. Rule 12-3024(7) and the Appendix B note require a non-ferrous plate where single conductor cables carry above 200 A per conductor. Rule 4-008 Appendix B note states that cables carrying
currents up to and including 425 A need only be spaced one cable diameter apart to minimize sheath currents and avoid derating. Aluminum plates at both ends satisfy both of these rules

Only single conductor cables carrying currents above 425 A per conductor would require an insulating plate at the
load end to eliminate the sheath currents and avoid derating the cables.

Note: The Appendix B note to Rule 4-008 on page 440 requires the use of an insulating plate at the load end of all
installations of underground single conductor cables to eliminate sheath currents due to the wider cable spacings.

Tony Moscioni
Electrical Inspector
Electrical Safety Authority


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