400 amp underground service.

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highvolts582

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brick nj
does anyone know what the minimum size parallel conductors alluminum or copper for a 400 amp service with 2 200 amp main breaker panels? I think 2 sets of 250 kcmils is good enough but my stomach is churning since Im 26 in my own buisness and my stomach churns at some seemingly simple descisions.

Thanks
Mike
Feel The Power Electric
 
to determine the "true minimum size" there are a few items which need to be clarified. Among them would be: (a) actual load ?, (b) seperate conduits ?, (c) is ambient an issue ? (d) are the conductors actually "parallel" such as to a meter base prior to being split to the two panels?
250 AL would be adequate, probably above minimum based on the above.
 
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specifics

i plan to use direct burial conductors. seperate pipes emerging from grade. to a 400 amp meter pan. ambiant temp should be no big deal im going to space the conductor sets about 2 ft apart in a 2 ft deep trench. im going to feed the panels with 4/0 copper cause its commercial. im just nervous about sizing the service lateral because Ive never had to do it the power company usually does the work and they size from there own set of "rules". the bulding has a load demand under 300 but i wanted to give the guy extra space and room to expand if anything ever comes of his unfinished basement.
 
since you are not terminating in a single overcuurent device, the service conductor can be sized by load. With a calculated load of less than 300, miniumum (per your request) would probably be 1/0 Cu or 3/0 AL.
If you wish to meet a possible 400 amp future load then the 250 AL or a 3/0 Cu should be adequate (ignoring voltage drop)
 
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