feeder size to 400a service

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Toros

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Tujunga, CA
Hi
Is A set of #500 mcm,cu wire good to supply 400A service via underground feed to a 400A service , single meter in an commercial bui?ding??


What if it was an residential 400A service , sigle dewelling??
Tanx
 
Edwardtomas said:
Hi
Is A set of #500 mcm,cu wire good to supply 400A service via underground feed to a 400A service , single meter in an commercial bui?ding??


What if it was an residential 400A service , sigle dewelling??
Tanx
Click to expand...
It's good if the calculated load, adjusted to 125% of continuous load is not greater than the ampacity of the service-entrance conductors before the application of any adjustment or correction factors (typically 380A), and also complies with 240.4(B) in conjunction with 240.6 (i.e. adjusted, corrected ampacity cannot be less than 351A).
 
and.,,,,,
in reply to the 2nd part of your question, if you comply with all the requirements of 310.15(B)(6) {'08 Code} you could use a 400 kcmil cu for a for a individual family dwelling unit.
 
It also depends on your voltage and the length of your conductors. Voltage drop could become a factor.
 
For sizing service feeders I only see table 310.15(b)(6) witch says for single phase 120/240 dwelling . Is their anouther table in the nec for 3phase services. Also when sizing service after you do your load calcs are you able to feed the service with feeders rated for the load or do you have to go buy size of service ?
 
liquidtite said:
For sizing service feeders I only see table 310.15(b)(6) witch says for single phase 120/240 dwelling . Is their anouther table in the nec for 3phase services. Also when sizing service after you do your load calcs are you able to feed the service with feeders rated for the load or do you have to go buy size of service ?
Click to expand...

As you stated, 310.15(B)(6) is only for dwellings. No such table exists for 3?.

You have to size the feeders/conductors for the OCPD. You choose the OCPD according to the load, then size your conductors to the OCPD.
 
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