I have moved in to a 30 year old house. Have put up portable ACs in all rooms. With one AC running at a time, there is no issue. But as soon as I switch on the second AC, the circuit breaker trips. Will changing to higher capacity breaker will resolve this ? Or I need to change to higher capacity wires or making new circuit - both seems difficult as I do not have any electrical diagrams

  • 2
    Changing to a larger breaker to prevent trips is how houses burn down. A circuit has only so much power that can be on it, why kitchens have more and larger circuits. Without know the AC units or the house circuits makes it hard to advise.
    – crip659
    Commented May 7 at 16:45
  • 3
    FYI, no homeowner ever has wiring diagrams unless they wired the home themselves and went way beyond the norm. Electrical plans for contractors show the locations of devices. Wiring is done on the fly and according to the electricians' knowledge and preferences. Hopefully the panel is labeled well enough for you to at least see what breaker serves what zone. If not, map the house, as suggested below.
    – isherwood
    Commented May 7 at 18:53
  • 1
    It is not recommended, but a 12 gauge extension on another circuit might help temporary.
    – crip659
    Commented May 7 at 19:59

3 Answers 3


JACK and UnhandledExcepSean's answers are 100% correct as far as breaker vs. wire issues.

I recommend doing a circuit breaker map of your house. You can do this one of two ways:

  • Turn off all the breakers and then turn on each breaker one at a time to see what works.
  • Turn off breakers one at a time and see what stops working.

At least in the US, a 30-year old house is generally in pretty good shape electrically (generally GFCI at least in kitchens and bathrooms, circuit breakers rather than fuses, grounding everywhere) so it is quite possible that you just have to identify which receptacles are on different circuits. It is quite common to have all the required circuits (kitchen, bathroom, laundry, etc.) and then have just one or two circuits for everything else - all the lighting and general purpose receptacles outside of the kitchen, bathroom and laundry. Some research - mapping your breakers/circuits to receptacles and lights - may uncover an extra circuit or two that you can use to put air conditioners on separate circuits.

In addition, mapping the breakers will help in the future if some other circuit trips or you want to do any electrical work such as replacing a switch or receptacle.


Not upgrading the wires and upgrading the breaker is a recipe for fire.

Upgrading wires and the circuit breaker can help, but if you have two powerful AC units on the same line, it would still trip the breaker.

Adding additional breakers are possible as long as you don't overload the main panel.


In general, if a breaker trips due to load, the breaker size needs to be increased and the wire along with it. If the breaker that's tripping is a small room breaker in the panel, then an additional circuit needs to be run. If the breaker that's tripping is the panel main breaker, then an increase in service from the utility is needed, more than likely, a larger panel, breaker and wire.

  • 2
    The better answer is probably to move some of the load to a different circuit, possibly a new circuit.
    – keshlam
    Commented May 7 at 18:38
  • @keshlam I think I included that. Just trying to answer all their questions.
    – JACK
    Commented May 7 at 21:05
  • Upgrading the wire and breaker really is not a viable solution for this situation. 15A and 20A receptacles cannot be on a circuit any larger than 20A. Going from 15A to 20A isn’t likely to let two air conditioners operate.
    – nobody
    Commented May 7 at 23:25
  • @nobody Right, deleted that part.
    – JACK
    Commented May 8 at 0:35

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