Long residential feeder [RE-wrenches]

[William Miller]

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Colleagues:

I wanted to see if there is a consensus on the subject of sizing long 
residential feeders.  I have some off-grid jobs coming up with feeders 
anywhere from 350 to 530 conduit feet and I need to specify feeder 
sizes.  Here's the philosophy I have been using, I'd be curious if anyone 
disagrees:

NEC 215.2 A (4) specifies feeders to not exceed 3% VD.  I agree this is 
appropriate for considering VD for the maximum draw I might 
expect.  Furthermore, I imagine that peak current draw will occur 
infrequently (or these customers are going to exceed the capability of 
their systems on a regular basis).

I base my calculations on a maximum draw of 50 amps for the larger off-grid 
residences I am now designing for.  If the VD approaches 3% at 50 amps, it 
is not much above 1% for 30 amp draws.  I figure staying in this range is safe.

Comments from this group are always greatly appreciated.

William Miller




__________________________________________________________________
William Miller
Miller Power and Communications
Voice :805-438-5600     Fax: 805-438-4607
email: wrmiller at mpandc.com
http://mpandc.com
License No. C-10-773985
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