I have a 100 amp box that has only 1 open slot for a single pole breaker. I have 2 unused 240v breakers (dryer and range) I was wondering if its possible to run a sub panel with 2 extra 120 volt breakers right next to the main panel.

I need a few extra outlets, one to supply power to the gas range and range hood and one for the dishwasher.

  • Hello, and welcome to Home Improvement. Good question; keep 'em coming! May 7, 2019 at 20:36
  • In MY breaker panels (but quite possibly not ALL breaker panels, even if restricting to 120/240V North American panels) you simply remove one 240V dual-pole that's not being used and you can put in 2 full-sized 120V single-pole breakers...not that I have anything against sub-panels, but do you actually even need one?
    – Ecnerwal
    May 7, 2019 at 21:33
  • 1
    Can you post a photo showing the space around the panel? Also, what make/model is the existing panel? May 7, 2019 at 23:07

2 Answers 2


You can use one of those double pole slots to feed a sub panel, I would get at least 12 slot main lug panel, the ground and neutral busses need to be isolated but you can do it. If you now have a gas range I would probably use that slot and leave the dryer intact, use the 40 or 50 amp breaker and size the feeder wire for the breaker size. You sub needed to be rated larger than the breaker you use, shouldn't be a problem finding a 12 slot 100a panel that you feed with your 40 or 50 amp breaker.


See if you can get a couple thin or tandem breakers to replace two of your existing full size breakers. If they're available, and you have the slots to support them, it's much easier than adding a sub panel.

  • 2
    A lot of new circuits need to be AFCI which is a problem for thin (1/2 size) breakers. May 7, 2019 at 19:30
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    It also depends on the brand, square D has an extremely limited selection when thinking about quads, also many panels cannot accept tandem breakers the panel must be listed for them to be legal. I would not want to get caught putting in a cheater (a breaker without the rejection feature) because if something went wrong and was done outside of code insurance may not pay.
    – Ed Beal
    May 7, 2019 at 20:25

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