sizing equipment grounding conductors

[dan hamilton]

When sizing equipment grounding coductors the table in 250-122 is
used requiring an 800kcmil aluminum conductor or 500kcmil copper
for a service rated at 4000 amps. If you parallel the conductors the
grounding conductor is bigger than your service conductor and your
electrode conductor. If I am pulling to a tranformer from the main
where would these grounding coductors terminate.

 

[charlie b]

You have me confused, I'm afraid. You are talking about a 4000 amp service, and you are talking about equipment grounding conductors. Those are two separate concepts. Can you clarify your question, please?

Are you asking about the Grounding Electrode Conductor, the one that goes from the service equipment to planet Earth? That is governed by Table 250.66, and the size is based on the size of the service wires.

Table 250.122 is used when you have a breaker that is serving downstream loads, with the Equipment Grounding Conductor being sized on the basis of the breaker rating.

Welcome to the forum.

 

[dan hamilton]

Sizing Equipment Grounding Conductors

Sizing Equipment Grounding Conductors

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Charlie Beck, Moderator

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Being that the exterior disconnect is the first means
of disconnect and the grounding conductor and the neautral condutor
are bonded to the grounding electrode at this point and the
grounding conductor is larger than all of the above will this impose
objectional current to pass through the path of least resistance(ie the
grounding conductor) or am i misinterpitng this requirment all together.

 

[infinity]

If I understand your question you asking about the EGC on the load side of a 4000 amp switch. According to 250.122 you are required to use a 500 kcmil Cu or a 800 kcmil Al conductor and you want to know what happens when parallel conductors are involved. Is this what you're asking?