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ohmhead

ohmhead

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ORLANDO FLA
Well question wire size to breaker size 240.4 the next higher sized brk can be used if conditions permit ?


Heres a example 500 mcm feeder the breaker is a 400 amp from switchboard to dist panel the panel has a 400 amp brk also were using the 2005 code on this job art 310.16 tables shows copper 500 mcm 75c at 380 amps .


Now i could make the wire match with 2 runs of 3/0 ?

In this example should we need to change or should the load on the feeder be the main factor ?


I feel it should be changed to the size wire to match that breaker and not just the load give me input to what you think.
 
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ohmhead said:
Well question wire size to breaker size 240.4 the next higher sized brk can be used if conditions permit ?


Heres a example 500 mcm feeder the breaker is a 400 amp from switchboard to dist panel the panel has a 400 amp brk also were using the 2005 code on this job art 310.16 tables shows copper 500 mcm 75c at 380 amps .
Click to expand...


As long as the load does not exceed 380A
 
Pierre C Belarge said:
As long as the load does not exceed 380A
Click to expand...


Well you say keep it per plan and use the 400 amp with the 500 mcm wire as the load is the factor even if we could make a wire change to bring it the max current .

Just never could understand why if you could make it right why not but i understand the load really is the factor .

What if in the future they max out the panel ?

Is there a art in the code which tells me the load is the factor ?





Thanks Pierre
 
What part of 240.4 (A thru G) are you trying to apply it to ? I'm missing something this is load side breakers, based on the defination of 240.1. Scope but your question is Line side for panel breaker in an MDP?

Secondly I'm not to debate the upsizing of the wire on the line side as you asked for comments, (or as I read into your Question) I will state 220.40, and hopefully it this article was used to allow the install of this existing circuit!

Yes, If your new calc's based on 220.40 or even 240 go beyond the sub panel size yes you might have to go larger. IE breaker and wire size, it just depends.

408.30 was mentioned true but again in the front of article 408.2 is more of an information gathering point,
and all the other code articles listed there state that these other Articles need to be met as well to make 408.2 fly.
 
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