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Old 09-29-2010, 04:09 PM   #1
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pvc and wire size


If I want a 30 amp sub panel in my garage and it is 100' from my main panel. What size wire and pvc do I need?

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Old 09-29-2010, 05:20 PM   #2
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pvc and wire size


4 #10 thwn and 3/4 conduit and a ground rod should set you on the right path.

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Old 09-29-2010, 09:11 PM   #3
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4 #10 thwn and 3/4 conduit and a ground rod should set you on the right path.
since it is 100' why not use #8? Voltage Drop

Still use 3/4 PVC and 4 wires
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Old 09-29-2010, 10:08 PM   #4
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pvc and wire size


Pulling the full 30a 240v @ 100' = 3% voltage drop
Which is acceptable
#10 is actually rated @ 35a...per 310.16....which means you could install a 40a breaker for 35a load & lower
Can't do the 40a breaker....not allowed to upsize the breaker on #10

I think I'd go to #8 & install a 50 breaker

Last edited by Scuba_Dave; 09-29-2010 at 10:35 PM. Reason: correction
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Old 09-29-2010, 10:16 PM   #5
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pvc and wire size


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Originally Posted by Scuba_Dave View Post
Pulling the full 30a 240v @ 100' = 3% voltage drop
Which is acceptable
#10 is actually rated @ 35a...per 310.16....which means you could install a 40a breaker for 35a load & lower
I think I'd go to #8 & install a 50 breaker
did you miss that little footnote about #10 Dave? See the asterisk on the wire size on the left and then it refers to 240.4(D)
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Old 09-29-2010, 10:25 PM   #6
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did you miss that little footnote about #10 Dave? See the asterisk on the wire size on the left and then it refers to 240.4(D)
Ah.....that means no upsizing the breaker -Yes = not allowed
I was thinking that was wrong (upsizing on #10).....but wasn't sure if it was allowed for a sub
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Old 09-29-2010, 10:50 PM   #7
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pvc and wire size


in some situations it is allowed but with it would have to fit within one of the exceptions listed in 240.4(D). I may have overlooked it but I found nothing to allow going to the next size breaker for #10 like you would be able to with feeders in general.

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