Equipment ground conductor

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codequestion

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I have a service switchboard which has feeder circuit breaker of 2500a. The feeder then goes to another room which feeds trough which then feeds two 400 amps fused disconnect.

How do I size equipment gnd based on two 400 amps or based on 2500 amp overcurrent protection? What does table mean when they say ahead of equipment for sizing equipment ground nec 2014?

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please clarify.

Which EGC are referring to?

The EGC size for The 2500A feeder?

Or the EGC for the 400A panelboards?

It sounds like you are tapping the 2500A feeder in the trough to power the 400A panels, no?

A one line diagram or a drawing would be useful.
 
jumper said:
please clarify.

Which EGC are referring to?

The EGC size for The 2500A feeder?

Or the EGC for the 400A panelboards?

It sounds like you are tapping the 2500A feeder in the trough to power the 400A panels, no?
Click to expand...
Feeder from 2500amp ckt bkr swbd to the trough.

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Size your egc based on the chart Bellow
898a6a8a3676eac37da54771d3ea11a0.jpg


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codequestion said:
Which would be ahead in my case?

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Click to expand...

In this context ahead means upstream of the grounded component, toward the source of the electrical power.
Among other things this appears to require (for this table anyway) that the EGC in the raceway for a feeder tap (whose protective OCPD is downstream) must be sized for the upstream breaker, protecting the wire which was tapped.
 
jumper said:
The EGC size for the 2500A feeder would be sized on 2500A.

Each EGC for the 400A taps to the panels would be sized for 400A.
Click to expand...

If these 400 amp conductors are tap conductors wouldn't the EGC run with the tap conductors be based on the OCPD ahead of the tap which is 2500 amps? Just not required to be larger than the tap conductors.
 
codequestion said:
I have a service switchboard which has feeder circuit breaker of 2500a. The feeder then goes to another room which feeds trough which then feeds two 400 amps fused disconnect.

How do I size equipment gnd based on two 400 amps or based on 2500 amp overcurrent protection? What does table mean when they say ahead of equipment for sizing equipment ground nec 2014?

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Click to expand...

if you provide a 350 MCM for the 2500 amp feed than you would provide 350 MCM for Taps.

There is a second part that does not apply to your question. The equipment ground never has to be larger than the CM area of the tap conductors
 
infinity said:
If these 400 amp conductors are tap conductors wouldn't the EGC run with the tap conductors be based on the OCPD ahead of the tap which is 2500 amps? Just not required to be larger than the tap conductors.
Click to expand...

Yes. Your last sentence is what I really should have noted.

If the taps were sized bigger than the minimum needed, the EGC would have to follow.

This is a good article for OP to read that states pretty much what you said verbatim.

http://www.ecmweb.com/qampa/code-qa-sizing-egc-feeder-taps
 
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