Art. 240.4

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Ben Trueblood

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I need some clarity on when the adjustment is allowed to be made concerning the overcurrent protection on a particular conductor. I have read the (3) exceptions but does anywhere else in the code over ride this Article?

I will give an example:
If I have a 400Amp circuit and I run 500 MCM copper which is according to 310.16 good for 380 Amps would I be in compliance by covering this conductor at 400 Amps? Is this only for service entrance conductors or does this apply to branch circuits as well.

Thanks for the insight.
 
Ben Trueblood said:
If I have a 400Amp circuit and I run 500 MCM copper which is according to 310.16 good for 380 Amps would I be in compliance by covering this conductor at 400 Amps?
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Yes, the over current protection could be 400 amps but the connected / calculate load would still have to be under 380 amps.


Is this only for service entrance conductors or does this apply to branch circuits as well.
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Service conductors, feeders and some branch circuits, not all branch circuits.
 
iwire said:
Yes, the over current protection could be 400 amps but the connected / calculate load would still have to be under 380 amps.

Service conductors, feeders and some branch circuits, not all branch circuits.
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I agree. Be sure about the calculated/connected load though. Some people just assume.
 
C3PO said:
I agree. Be sure about the calculated/connected load though. Some people just assume.
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I think that there is a lot more assuming than actual calculating. How many times have you seen calc sheets on the job?
 
SEO said:
I think that there is a lot more assuming than actual calculating. How many times have you seen calc sheets on the job?
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If there are E sheets there should be calcs on them, at least in Az. there is.
 
benaround said:
If there are E sheets there should be calcs on them, at least in Az. there is.
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Agreed, here in Utah it is the same. On any commercial or industrial job there should be engineered plans and the branch circuits, feeders and services should all have calculated loads.

Chris
 
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