I am building a 12'x12' shed and want to run some electricity. I will have 2 20 amp circuits and 1 15 amp circuit for the lighting. I will run wire from the main panel on side of house to new sub panel in shed. Distance to shed is about 120 feet from main panel. What size sub panel would you install 40, 50 or 60 amp panel and what gauge wire would you use for the amperage suggested.

I have not heard from tkrussell in a while.

thanks

Quote:

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Originally Posted by loupi01

What size sub panel would you install 40, 50 or 60 amp panel and what guage wire would you use for the amperage suggested.

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First of all : all domestic power wiring exceeding 90' at 50 amps or higher requires 4/0 wire. To save money you can use aluminum conductors.

References :

List 1 : wire-gauges

List 2 : amps-wire gauge

With 2 20 amps circuits and 1 15 amps circuit your feeding breaker should be 60 Amps.
You can use 3 x 4/0 cable (25 mm = 1" diameter).
Install underground in conduit.
Success!
;)

Loupi,

Please ignore post #2. This is based on 12v circuits and is completely irrelevant to what you are doing at 120/240v.
The notion of 4/0 wire for a 50a-120/240v feeder at 90' is ludicrous.



For a 50A sub-panel run #6cu in conduit out to the shed. 120' is not that far and the voltage drop is WELL within spec even at the full 50A/240v.
The small amount of 120v circuits you will have will be of absolutely NO consequence, even if partially imbalanced.

Thanks stanfortyman,
I understood the information from Credendovidis was not for my application when I read it. Do you think I would be able to up the sub panel to a 60A using #6cu wire with the 120' distance? Also what # ground should I run?

Thanks

The thing about voltage drop is it is ONLY a concern with regard to the load. You can run #6 to a sub-panel in conduit the whole way on a 70A breaker. 120' is not that far.
IF you were to draw over 60 or so amps there will be more than a 3% drop in voltage. This is more then the recommended amount of drop, but it is still within reason and will not do any harm.

If you use a 60A breaker you will be FINE, even at a full 60 amp load on the panel.

Thing is, if you will use any NM cable as part of this circuit you cannot use a 60A breaker, you would need to drop down to a 50A. THHN conductors in conduit are rated higher than NM cable for this size wire.

Thanks stanfortyman,
You have been very helpful

Quote:

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Originally Posted by Credendovidis

First of all : all domestic power wiring exceeding 90' at 50 amps or higher requires 4/0 wire. To save money you can use aluminum conductors.

References :

List 1 : wire-gauges

List 2 : amps-wire gauge

With 2 20 amps circuits and 1 15 amps circuit your feeding breaker should be 60 Amps.
You can use 3 x 4/0 cable (25 mm = 1" diameter).
Install underground in conduit.
Success!
;)

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UMMMM What!!