Can I put one circuit on two 20-amp breakers? I'm drawing too much power on just one breaker and I'm not able to run a whole new circuit right now.

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    I've up-voted this because I'm sure there are a lot of tyros who are wondering exactly the same thing. Just because the pros know this is an awful idea doesn't mean we shouldn't document it. Aug 6, 2016 at 13:15
  • I'm not sure I understand the question. Are you proposing splitting the hot leg in the panel?
    – isherwood
    Aug 8, 2016 at 16:02
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    @DanielGriscom: Is a "Tyro" a variation on a "Pyro"?
    – wallyk
    Aug 8, 2016 at 16:48
  • @wallyk Nice! I spent a couple of minutes finding a good definition of "tyro" that I could post for you, but then finally got the joke. Aug 8, 2016 at 17:25

3 Answers 3



First -- the job of the breaker is to protect the wire from overheating and BBQing your house. A 40A circuit would require 8AWG copper wire, not the 12AWG that is currently in your walls.

Second, you are not the circuit breaker factory, which means you have no idea how such a combination would perform, and are forbidden from doing this by NEC 240.8:

240.8 Fuses or Circuit Breakers in Parallel. Fuses and circuit breakers shall be permitted to be connected in parallel where they are factory assembled in parallel and listed as a unit. Individual fuses, circuit breakers, or combinations thereof shall not otherwise be connected in parallel.

  • Exactly. There's a whole slew of things that could go wrong, don't even try.
    – Mast
    Aug 7, 2016 at 10:08
  • That is, assuming that they live in the U.S.
    – AStopher
    Aug 7, 2016 at 22:23
  • @cybermonkey -- it's a bad idea no matter where you live, really. (Point me at an electrical code that allows this.) Aug 7, 2016 at 23:23
  • Good answer, but OP didn't state that this was on 12AWG wiring. Could be 8, but with a smaller breaker. Which I have recently encountered - probably done by the guy who used to own my house - though I admit it's probably rare.
    – 3Dave
    Aug 8, 2016 at 4:16
  • @DavidLively -- it is true that upsized wiring happens occasionally, usually to control voltage drop on long runs. It still doesn't change 240.8 though! Aug 8, 2016 at 4:59

Of course not.

You are talking about defeating circuit protection because you find it inconvenient. Obviously, this is dangerous. ThreePhaseEel goes into the gory details of how it'll burn your house down, but let's look at other options.

Map all your outlets and circuits.

Buy a half dozen night-lights at the dollar store. Turn off computers that are not laptops. Go through your house, turning off one circuit at a time, and go see which devices or outlets die when you do. I just did this, marking the breaker and outlets with different colored tape, you can label the breaker number on the outlet if you prefer. The night-lights are easy ways to see if an outlet is hot -make sure they are switched on!

Once you've mapped which circuits feed which outlets, you can check for the most common situation: someone has over-stacked one circuit while the other circuits are barely used. This can be easily fixed by rearranging things.

We had one guy who had an 850 watt gaming PC and a big laser printer, and an A/C unit too. He was very committed to make them work on the same circuit. Turns out, there was a different circuit right in the same room and he hadn't realized. Moved the laser printer to that; solved.

Rethink your energy use.

I just fired up an air conditioning unit, plugged in through a Kill-A-Watt energy monitor ($20). The Kill-a-Watt actually screamed in pain (did you know they can do that? I didn't). The A/C was drawing 17 amps. It was broken (nearly out of freon) but even fixed, it was inefficient. New units of that class draw 6 amps because their efficiency is that much better. So if you are using a decrepit old air conditioner, it needs to go into the trash, as it will cost you more in electricity than a new one costs to buy. Seriously.

A dehumidifier in the same room as an A/C unit is a mistake. A/C already dehumidifies.

All the energy you spend in a room turns into heat. You must use more energy still, to pump the heat away with an A/C unit. So any energy you save, you save twice. A tester like a Kill-a-Watt will help you identify those.

Can your laser printer live in a different room that you're not struggling to air condition? They make long Ethernet cables. (Or maybe your printer offers WiFi, so it doesn't even need a cable.)

Do you really need to use that 850 watt gaming PC right now? Can you get your work done on a laptop plugged into your big monitor (which doesn't take much energy)? Stuff like that.

One guy actually figured out that his $4000 Mac Pro pays for itself in 4 years by being more efficient than his old high end PC. And he could still run Windows on it.

Convert the circuit to 240 volts

Certain rooms in your house need a specific number of 120V outlets (e.g. within 6 feet of any point on the wall, in bedrooms). This doesn't work if converting a circuit will break any of those rules. However, it's possible in some spaces.

This will double the amount of power on the circuit, as you originally hoped. However, the rules are byzantine. Each of the loads on the circuit must be 1440 watts (6 amps) or more, and it can't include lamps. I would argue that a qualifying load could be a 1500W step-down transformer with multiple loads plugged into it. But your local electrical inspector might disagree.

In this case, you change every outlet to NEMA 6-15 or 6-20, remark the wire formerly known as "neutral" to be another hot, and punch it down into a 2-pole 20A breaker.

  • After traveling recently to another country that uses 240V, I checked a few of my appliances, computers, etc. around my house (in addition to the electronics I was traveling with) and I was surprised how much stuff accepts both voltages in the U.S. Obviously many electronic appliances would require an adapter or a new power cable, but the circuitry supports it.
    – user4302
    Aug 6, 2016 at 20:39
  • "The Kill-a-Watt actually screamed in pain" - is this a feature, or did you overload it somehow and break it? These are only rated for 15 amps from what I can find on google.
    – Random832
    Aug 6, 2016 at 21:34
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    @Harper -- the main issue with that is 210.6(A) which restricts the voltage between the terminals of luminaires and receptacles feeding loads less then 1440VA/&#00BC; in dwelling units to 120VAC. (Although I don't quite understand what they imply "terminals of luminaires" to be -- if it's the user-accessible terminals on the lampholder, then every fluoro fixture violates that, and if its the wiring going into the j-box, then what's the point?) Aug 7, 2016 at 15:19
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    I will say that your 850 W gaming PC doesn't draw 850 W when you're checking email and writing Word docs (as long as it's a relatively recent build). Modern CPUs reduce clock speed when possible to save energy, and GPUs (the big power draw in a gaming computer) are mostly only used when gaming.
    – mmathis
    Aug 8, 2016 at 14:17
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    @Harper Definitely measuring with a Kill-a-Watt is the best way to determine the power draw of your PC. Even with an inefficient supply, I'd be surprised it it was drawing more than an amp or two unless it was under full load (e.g., while gaming)
    – mmathis
    Aug 9, 2016 at 15:24

Split it up & add an additional 20A circuit & use the other 20A circuit for what you were going to use it for. Refer to NEC for further info

  • 1
    To where in the NEC should the OP refer? This answer doesn't add much without that reference
    – mmathis
    Aug 8, 2016 at 14:18

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