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I'm trying to power a shed that's gonna pull about 1000W max. My outside service box is full and I cannot add a 30A breaker.

In my service I have a 50A breaker that's powering my oven. The oven on max power would pull a potential of 11,400 watts. It's a 2p 50A breaker with 10/3 going to my oven.

My question is: can I come off one pole on that 50A breaker and run a 12/2 120V circuit to a 30A breaker inside my shed?

I can upgrade to breaker to a 60A which will handle 14,400 watts if need be. I'm just worried about the current making the 10/3 circuit overheat an burn my house down. Solutions or thoughts?

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  • Pictures of your panel would help a lot.
    – manassehkatz-Moving 2 Codidact
    Commented Jul 2 at 3:02
  • 3
    Don't connect a 20A circuit off a 50A breaker. Just don't. Please.
    – KMJ
    Commented Jul 2 at 3:24
  • 1000W is 8.3A at 120V, so I don't know where you got the idea you need a 30A feed anyway. As for your proposed and exsiting code violations, might be time to fix the whole mess, right, not cobble on another code violating bad idea to help burn your house down.
    – Ecnerwal
    Commented Jul 4 at 1:36

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I am a bit concerned about 10/3 on a 50A circuit for your oven. A 50A circuit usually requires either 6 AWG or 8 AWG copper (depending on wire/cable type) or 6 AWG aluminum. 10 AWG sounds like:

  • Original oven was 30A (quite common)
  • New oven required 50A circuit, but installer was lazy and/or cheap and instead of running new wires/cables just changed the breaker

If that's the case, you have a serious problem already. As in, the oven running at as much as 47.5A (11,400W / 240V) is already much larger than the 10/3 cable is rated to handle.

As far as adding the circuit for the shed, 1,000W is not a lot. In fact, that could fit on an existing 15A or (better) 20A circuit. You actually don't want to put it on a 30A or larger circuit because then you would not be able to use standard 15A or 20A receptacles. And you definitely don't want to piggyback it on an existing even larger circuit.

Assuming your existing panel is full, the place to double-up is not on a 30A or larger circuit. It is on a 15A or 20A circuit that is not dedicated to a particular location. There are certain 20A circuits which are supposed to be dedicated to:

  • Kitchen (at least 2)
  • Bathroom (at least 1, but possibly 1 per bathroom)
  • Laundry

and occasionally others. If the above circuit are not dedicated you generally still shouldn't add to them because if they are legitimate (grandfathered) you can't make them worse by adding more stuff.

But generally you will have at least a few general-purpose 15A or 20A lighting/receptacle circuits. Add the shed to one of those circuits. Note that the shed will require GFCI protection, so if you add to a circuit that is not already protected then you need to add GFCI either in the house part of the circuit or at the first point of use in the shed.

In almost no situation would you run 12/2 to a 30A breaker in the shed. It runs from a breaker to the shed, and that breaker must be 20A, not 30A. If you actually need 30A and 1,000W max. that just doesn't add up - 1,000W at 120V is less than 9A, so a 30A breaker would be overkill anyway.

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