Wiring a shed with 12/3


Old 11-30-19, 04:10 PM
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Wiring a shed with 12/3

Hi - I'd like to run power out to my shed which is about 12' from my house. I have extra 12/3 wire already run from my main breaker box through my garage and crawl space and could fairly easily continue it out to the shed in a conduit. My questions are:
1) am I able to do this with 12/3 wire? Not having to tear up drywall and rerun different wire would be great.
2) what will I need once I get into the shed? I don't need anything fancy and won't be using power tools out there and won't need a heater/AC unit. I'd like to have two lights, two interior outlets to charge batteries, etc. inside the shed, and then, if possible, I'd like to run a wire continuing on about another 40' from the shed to a external outlet to be able to plug in my lawnmower or leaf blower.

Do I need a small breaker box in the shed? We just had a new electrical panel installed last year so have lots of space to add on.

Any advice would be very much welcomed. Thanks.
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Old 11-30-19, 07:12 PM
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The 12-3 will work fine and give you two 20 amp circuits.

You could continue one of the circuits out the 40' to the receptacle for the lawn mower, etc.

No need for a subpanel out in the shed for now. You would need a 20 amp double pole toggle switch to be the "master" switch for the shed.

A breaker panel in the shed now won't do any good. Yous till need a breaker for the shed feed back at the house panel which would be 20 amps for the 12-3 wiring, and if you did overload the line it is anyone's guess which breaker will trip first if you had a shed panel..

If you nstall a larger size conduit out to the shed now, then you could upgrade the wiring at a later date without digging up the yard again.
Old 12-01-19, 07:10 AM
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The 12/3 if a cable needs to be type UF to go underground in conduit. Type NM is not allowed in wet locations.
Old 12-01-19, 09:07 PM
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Thanks, Allan. I appreciate the advice.
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