450 amp residential service

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R@rpe

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hello,
I'm looking for opinions:
I am going to feed a 450 amp 240 volt 1-phase residential service.
Since 310.15 (B) (6) only goes up to 400 amps -
Would you parallel two sets of 250 kcmil or 300.
The wires will be run in one 3'' PVC conduit.
The Meter can is a 450 transocket
 
R@rpe said:
hello,
I'm looking for opinions:
I am going to feed a 450 amp 240 volt 1-phase residential service.
Since 310.15 (B) (6) only goes up to 400 amps -
Would you parallel two sets of 250 kcmil or 300.
The wires will be run in one 3'' PVC conduit.
The Meter can is a 450 transocket
Click to expand...
I assume you mean aluminum. I would parallel 300 kcm. 250 kcm at 75C is only good for 410 amps.
 
no copper,
I believe that one conduit will require an 80% deduction on the conductors.
But I want to know if I should be using 310.16 or if I can somehow use 310.15 (B) (6)
 
You can't use 310.15(B)(6) for a 450 amp service since it is larger than the Table allows. You must use Table 310.16.

Chris

P.S. I am moving this thread to the NEC forum, since it is not related to hazardous locations.
 
R@rpe said:
no copper,
I believe that one conduit will require an 80% deduction on the conductors.
But I want to know if I should be using 310.16 or if I can somehow use 310.15 (B) (6)
Click to expand...

I agree you cannot use 310.15(B)(6). Since 250kcm copper is rated 290-- assuming a 90C insulation you can derate from there. 290 *2= 580.

580*80%=464 amps. I say go with 250kcm copper
 
The ironic thing here is that if you had used the Table 310.15(B)(6) 250Kcmil copper

would of been the only choise. Well at least the Table wasn't used.
 
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