Contractor Shack Feeders

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cainta

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I'm designing a Contractor Row with 12 70A power pedestals 14' apart. Contractors would plug their office shacks into the power pedestals. I would design for one run of 120/208V feeders and tap at each power pedestal, alternating phases AB AC BC. I know I do not have to make previsions for 840 AMPS! Is there a de-rating factor in NEC I can use? Article 550.31 might apply, but I had trouble understanding it. Any thoughts?

[ October 07, 2005, 06:16 PM: Message edited by: cainta ]
 
Re: Contractor Shack Feeders

Humm.....
550.30 says "shall be single-phase, 120/240 volts, nominal." No three phase 208/120V! So figure a single phase transformer and 240/120V for a start and then figure the likely load each trailer would have, multiply by 12 and multiply the total by 27% to find your answer. However, be sure to do the original load calcs correctly!

I didn't know mobile homes came with 70A cords??!!

I think after 50A you would need to "hard wire" the trailers?

And yes, 550 does apply to your situation.
 
Re: Contractor Shack Feeders

Originally posted by websparky:


I didn't know mobile homes came with 70A cords??!!

I think after 50A you would need to "hard wire" the trailers?
Click to expand...
The 'power pedestal' has a 50A breaker for a 240V outlet and a 20A breaker for a couple 120V outlets. 70A at the termination. FYI
 
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