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On our property we have a older shed (10 x 10) connected to the main panel by a 15 AMP breaker( the direct burial wire is 14/2). I've extended that shed and want to add more outlets and overhead lights.I'm want to upgrade that breaker from a 15 to a 20 AMP, then use 12/2 romex inside the shed and 12/2 underground.. Do i need to remove the older 14/2 direct burial wire completely or can it just be disconnected? Also ,am i correct in thinking i can old run one connection to the shed, as well as the older wiring in the shed which is 14 /2 needs to be changed out for the newer 12/2, due to the higher breaker?

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  • I would use buried plastic conduit Chances of hitting with a shovel in a couple years are too great, at least in my yard. Commented Mar 21, 2021 at 17:20

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Can you abandon the old wire in place? Sure. Well, technically I think I recall reading something in NEC about removing permanently-abandoned wiring where feasible -- let's just say it's infeasible to remove that direct-bury cable and move on.

Yes, if you up-size to a 20 A breaker you'll have to replace the 14 gauge wiring in the shed with 12 gauge.

So far as circuits and wiring from the house to the shed goes you have options. A detached building is allowed to have a single branch circuit or a feeder circuit. Choosing the feeder option entails installing a subpanel in the shed and a grounding electrode system too (it's not terrible, just a little more work and cost than you had in mind).

"A single branch circuit" actually means more than a person would expect. If you wire that as a "multi-wire branch circuit" (MWBC) then you can have two 20A, 120 volt lines going out there while still calling it one circuit.

There is another trick for gaining an extra circuit: Add some kind of outdoor lighting on that shed. You can have a switch in the house that controls the power to that lighting circuit. You can also have a switch in the shed that controls the light. And if there are a few outlets on the circuit too, that's ok.. To complete the idea, just leave the switch in the house turned on all the time so that the outlets are always live and ready for use.

The new wiring to the shed needs to be UF-type cable which can be direct-buried or pulled (wrestled) through a grossly-oversized conduit, or else conduit with wet-rated loose conductors like THWN. Don't use NM ("Romex") cable for the underground portion. The conduit wiring method is unfamiliar to many people, but it's worth consideration.

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You are correct that you are only allowed 1 circuit to an outbuilding. However, there are some exceptions. One of those exceptions is for different (e.g. specialty) uses.

A perfect example here would be allowing you to switch the lights on/off from the house. As in "whoops, left the lights on in the shed, I don't feel like going to get my galoshes, so I'll just throw this light switch right here". Or likewise, controlling an outside light attached to the shed (nevermind the fact that you later changed it to a sensor-operated light).

So, if you are willing to reroute the #14 to a light switch, you can keep it. And yeah, there can be outlets on the switched circuit.

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  • Just so i understand correctly,my current #14 i can reroute and just use for the lights ,and the new 12/2 in going to lay will be just used for receptacles?
    – Jben04
    Commented Mar 22, 2021 at 11:54

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