new 400 amp resid. service

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NolaTigaBait said:
yeah , i was talking about #3 nm feeder....why would you have to use #2?
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If you read 334.80, it states that nm can be used for 60C unless you are derating. The final ampacity must not be more than 60C
 
man, i forgot about that one....thanks....one of the last jobs that i did with my ole boss...we had a 200 main breaker panel in front of the house and we fed a 2nd panel in the back with a #2 feeder!!!!....of course he was going by 310.15b and I thought that this was ok, until i started reading on my own....the thing that doesn't make sense is that the main is fed with 2/0, but acccording to code, we would need a 1/0 feeder for a 125 main subpanel!!!
 
uhhhh, why i can't use let's say #4 for a 100 amp feeder where there are two panels in one house....why can't i use table 310.15b?....i understand why I can't use it....i want to understand the from the engineering aspect of it
 
NolaTigaBait said:
uhhhh, why i can't use let's say #4 for a 100 amp feeder where there are two panels in one house....why can't i use table 310.15b?....i understand why I can't use it....i want to understand the from the engineering aspect of it
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Not sure, only that the NEC probably feels ART 220 is over rated for dwelling units.
 
NolaTigaBait said:
uhhhh, why i can't use let's say #4 for a 100 amp feeder where there are two panels in one house....why can't i use table 310.15b?....i understand why I can't use it....i want to understand the from the engineering aspect of it
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It has to do with the diversity of the load. Table 310.15(B)(6) uses the diversity of the loads of a dwelling. When you split up the feeds that diversity is no longer applicable and you would need to use 310.16
 
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