After moving into my new home I noticed there was only one 20 amp breaker in the box. The AC unit was wired into it but since it was winter and I didn't need AC I unhooked it to wire in the 220 for my dryer. My question is can I take one of the empty 15 amp breakers in the box and change it out to a 20 amp so I can have my AC and dryer both wired in?


  • 1
    What make and model is the breaker box? Jul 12, 2018 at 2:11
  • 1
    Also, your AC is a 240V unit, right? Jul 12, 2018 at 2:11
  • 2
    Is the the USA? Or where in the world are you located? What’s the spec for the dryer? Those are usually on 30 amp breakers.
    – Tyson
    Jul 12, 2018 at 2:20
  • If this is the USA, this question makes no sense. First an electric dyrer circuit is 30A (5000 VA)? Second is the AC 240V and if so what is its running amperage or kw? Third since 1965 there have been at least 3 20A circuit breakers in every panel, 2 - 20 Jul 12, 2018 at 13:08
  • and 1 20A laundry circuit. Jul 12, 2018 at 13:14

3 Answers 3


Yes you can swap breakers out, but take extreme care to match wire to breaker. Don't use 14 gauge (generally white) wires for a 20 amp circuit. Also note that most 220V circuits in the USA require a tandem breaker taking two slots.

Investing in an electrical permit is highly recommended, if your jurisdiction will inspect at the end of the job.

  • OP's wires already exist - as you will note op is swapping out Dryer instead of AC in the winter - because in the summer clothes can be dried outside. Op only has one 20AMP breaker but obviously has existing wires. Op simply no longer wishes to be swapping them.
    – Ken
    Jul 14, 2018 at 22:01

Assuming this really is a 110V AC unit, which was originally hooked to a 20 amp circuit breaker, and assuming that that your service will support the additional load in your breaker panel, then yes you can replace a 15 amp circuit breaker with a 20 amp circuit breaker. (Be sure to kill the main power coming into the breaker panel before working on the breakers themselves. You probably have 200 amps coming into the panel and an errant screwdriver will kill you.)

Of course, you are also assuming that the wiring for the AC unit is the correct gauge. For 20 amp, the wire for the circuit should be 12 gauge, not 14. If this is newish construction, and in the US, the wire will typically be yellow, not white and you can read the gauge on it. If you don't know for sure, measure the diameter of the conductor (copper wire without the insulation). 12 gauge wire is 0.08 inches in diameter. 14 gauge is 0.064.

If it is 14 gauge wire, and again assuming the US, it is against code to install a 20 amp breaker, and more importantly you run the risk of a fire to do so. In that case, hire an electrician to pull the correct gauge wire.

Lastly, I would inspect the AC unit itself and make sure it is really just 110V/20 amp.


Yes given the following is true:

What you are asking is can you re-purpose the panel slot where you have a non-used 15 amp breaker , remove it and install a 20 amp breaker and then hook your existing dryer wire to that new 20 amp breaker?

If your panel will allow you to install a 20amp breaker there then Yes you can.

See picture below as an example

Picture of an existing scenario vs Desired Scenario

By All means there should be no reason that you could not do it - except and unless your panel prohibits a 20 amp breaker in that slot.

EDIT 7-14-2018

For those that took that quick thought on the OPS question and were thinking about wire ratings Please read the OPS question again.

The Op has two wires coming into his panel : One for his Dryer and One for his AC. The WIRES already EXISTS. The Issue is the OP only has one 20AMP Breaker in his panel. Op wants to know if an UNUSED 15 AMP breaker slot Can be converted for use with a 20AMP breaker by installing a 20AMP Breaker!!

  • There is a very good reason not to do it, and that is if the wire in the wall is only rated for 15A. If you run 20A on a 15A wire you can end up with the wire overheating and starting an electrical fire. Jul 12, 2018 at 11:42
  • Not only that but requires dryers to be sized at 5kw minimum.
    – Ed Beal
    Jul 13, 2018 at 3:36
  • @TheEvilGreebo HIS WIRE was already hooked to the 20AMP - OP simply disconnected the AC wire from the CB so he could connect his DRYER to that 20amp CB. The wires already exists and are 20amp rated. OP only had one 20AMP breaker - so op simply swapped witch one was connected during the winter!!!!!! He is putting in a 20AMP so he has 2 - 20AMP breakers one for the PRE-EXISTING wire that goes to the AC, and One for the PRE-EXISTING wire that goes to the dryer.
    – Ken
    Jul 14, 2018 at 21:47
  • @EdBeal - You know I like you Ed (and you are correct about the wires) but please Read the OPS question again - he is not running new wires, the wires for his Dryer already exist, the wires for his AC already exist. OP has been swapping Dryer in the winter , AC in the Summer (as clothes can be dried outside in the summer). The wires exist - op only has a single 20 amp breaker (which is why op is swapping summer and winter) - both AC and Dryer wires are in the panel because they already exist - op simply wants to not be swapping every year by adding in a 20AMP in place of an unused 15amp.
    – Ken
    Jul 14, 2018 at 21:56
  • If the panel is changed code requires it to be up to current code this is a minimum of 5kw or the nameplate value witch ever is higher.
    – Ed Beal
    Jul 15, 2018 at 17:12

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