# Common Grounding Electrode And Tap



## Black Dog (Oct 16, 2011)

What year NEC?


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## Captain Nordy (Jul 13, 2014)

2014


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## ghostwriter (Nov 1, 2007)

You show the 200 amp equipment being feed with 500 kcmil.

Is that correct?


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## Captain Nordy (Jul 13, 2014)

ghostwriter said:


> You show the 200 amp equipment being feed with 500 kcmil.
> 
> Is that correct?


Nope. I just copied and pasted too fast. Sorry about that. Should be 3/0


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## ghostwriter (Nov 1, 2007)

Thank you,

I agree with your answers.


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## Captain Nordy (Jul 13, 2014)

Excellent. Thanks.


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## McClary’s Electrical (Feb 21, 2009)

Black Dog said:


> What year NEC?


Why? Did 250.66 change lately?


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## Black Dog (Oct 16, 2011)

mcclary's electrical said:


> Why? Did 250.66 change lately?


250.64 has a lot of new wordings....


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## FaultCurrent (May 13, 2014)

250.64

(1) Common Grounding Electrode Conductor and Taps.

A common grounding electrode conductor and grounding
electrode conductor taps shall be installed. The common
grounding electrode conductor shall be sized in accordance
with 2S0.66, based on the sum of the circular mil area of the
largest ungrounded conductor(s) of each set of conductors that
supplies the disconnecting means. If the service-entrance conductors
connect directly to the overhead service conductors,
service drop, underground service conductors, or service lateraL
the common grounding electrode conductor shall be sized
in accordance with Table 2S0.66, note 1.

You don't have enough information to answer the question. Are the three disconnects fed by one set of service conductors and then tapped to each enclosure or are there 3 sets of individual service conductors fed by a service drop or lateral?

One scenario could be a set of 1000 Ampere or larger conductors feeding the three disconnects. Adding up the tap conductor sizes is incorrect. But by accident in this case the total ended up over 1100 kcmil so 3/0 is the default answer.

To be a devil's advocate, lets say we install 3 500 kcmils in a gutter to feed three future tenants. But at the moment we only install 3 #2 taps to 3 100 amp disconnects. Would the common tap be based on adding up the area of 3 #2's ?

The other scenario would be three risers to three service heads. Then you would use 250.66 Note 1.


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## Captain Nordy (Jul 13, 2014)

230.40 Exception 2


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## Carultch (May 14, 2013)

FaultCurrent said:


> To be a devil's advocate, lets say we install 3 500 kcmils in a gutter to feed three future tenants. But at the moment we only install 3 #2 taps to 3 100 amp disconnects. Would the common tap be based on adding up the area of 3 #2's ?


I always like the challenge of interpreting the NEC for potential future work.

My opinion is to always count all spare equipment as active, until you reach a designated demarcation between current work and future work, that is easy to revisit.

In this scenario, I see the tap conductors as equipment that should be counted as active, even though it only feeds equipment reserved for future use. The reason being, is that tap conductors can be difficult to deenergize. When you come back in a year to do the future work, you don't want to have to rip out the EGC/GEC wiring that is routed with the energized tap conductors. Instead, it is much better if the tap wiring assemblies are complete, when they are first installed.


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