Electrical Box Wire Size for an Air Conditioner

Gauge

• A wire’s gauge refers to its thickness and capacity to handle different electrical loads. The thicker the wire, the lower its gauge number and the more electricity it can handle. The National Electrical Code uses the AWG wire numbering system to specify gauge. For a standard 220-volt 30 amp window air conditioner, use an AWG No. 10 gauge wire. For a smaller 110-volt 20 amp air conditioner, use an AWG No. 12 gauge wire. Refer to the nameplate next to the energy box on the back of the unit for the most accurate information regarding wire gauge for your appliance.

Length

• Most people place their air conditioners within reach of an electrical outlet, so length is generally not an issue for concern. Ensure the wire is long enough to connect the energy box to the wall outlet without stretching or bending, as these conditions can damage the wire over time. If the wire is longer than 300 feet, use a thicker wire with a lower AWG number to reduce voltage drop.

Plug

• Most air conditioners require a three-prong plug to function properly. Check to make sure your outlet works with three-prong plugs before purchasing your unit and install a three-prong outlet if necessary. You may need to hire an electrician to change your outlet to meet your unit's requirements. Check the manual for the most accurate information on the unit’s plug and outlet requirements.

Warnings

• When working with your air conditioner’s electrical wiring, always use caution. Turn off the circuit breaker in the room you plan to install the air conditioner prior to installation to avoid electric shock. Have the unit installed and tested by a professional if you are unsure about your abilities to install it safely. Never overload electrical outlets or use wires that are thinner than the recommended size.