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Need help with service calculation ??? #179040 06/23/08 10:09 AM
Joined: Jun 2007
Posts: 19
S
site351 Offline OP
Member

Got a question and don't have a code book....

A 3" P.V.C.conduit is ran from under ground transformers
to electric meter packs with 150 breakers. All meter packs
are main lug, no main breaker. Some meter packs contain six
meters and some five, some four. 120/240 volt residential.
I know I can parallel the Pratt 250-250-4/0 alu. in a 3"
p.v.c. pipe...is that big enough to handle the load for
the five and six meter packs ?
6x 150= 900 total amps for the six banger @ 45% = 405
amps ? can't remember how much to derate...
Five meter pack may work with 250...just not sure about the six ... thanks....

2017 / 2014 NEC & Related Books and Study Guides
Re: Need help with service calculation ??? [Re: site351] #179041 06/23/08 11:14 AM
Joined: Dec 2002
Posts: 317
S
sabrown Offline
Member
Assuming that you have done calculations on the services and have found that they all are at 150 amps. 5 residential services can be calculated at .45 for a total of 337.5 amps (see 220.84).

6 residential services can be calculated at .44 for a total of 396 amps. Same code reference. Parallel conductor installation of 250 kcmil are good for the 400 amp total (255x2x.8 NEC 310.15(B)(2)(a)) if allowed by your AHJ.

I did not check the nuetral. This also makes the assumption that you meet the multi-residential requirements.


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