Upgrading An Electric Line For An Air Conditioner

18 May 2015
 Categories: , Blog


Sometimes your old window air conditioner can't take the heat, and you need to upgrade to a larger unit. However, air conditioners are big power consumers, particularly when the compressor is activated.

If a new air conditioner trips your circuit breaker whenever the compressor comes on, you will need to either upgrade the existing line, or add an additional single use line for your air conditioner.

Upgrading an Existing Single Use Line

Most residential electric service uses fifteen and twenty amp lines. A fifteen amp line is sufficient for most needs, but for larger appliances, a twenty amp line may be required. 

An air conditioner should be connected to a dedicated line, which is for a single use and is connected to a single outlet. If you have a dedicated fifteen amp line that cannot handle a larger air conditioner, you can upgrade the line to twenty amps.

You will need the following items:

  • Twenty amp breaker. Check the brand name of your breaker box, and buy a breaker from the same manufacturer. They are not universal.
  • Twelve gauge wire. Measure the distance from the outlet to the breaker box, but allow several more feet of wire, it usually doesn't run in a straight line.
  • Wire cutter/stripper. To cut wire to length and strip insulation from the ends.

You will begin by turning off the main breaker to the house. Using a flashlight, open the breaker box and remove the breaker from its slot by prying it out from one side with a screwdriver. Unhook the black and white wires from the breaker, and the green or copper colored wire from the grounding bar inside the breaker box. 

After pulling the wires through the opening in the side of the breaker box, you can turn on the main breaker, so you don't need to work in the dark.

Remove the cover plate from the outlet, then remove the outlet by loosening the screws that fasten it into the outlet box. Remove the three wires from the outlet.

Pull the outer jacket away from the end of the twelve gauge wire, and strip two inches of insulation from the end of the wires inside. This is done by pulling the wire through the slot in the wire cutter blades that is marked "twelve" , for twelve gauge wire. 

Twist the ends of the wires with the ends of the corresponding wires that you disconnected from the outlet, then bend them as much as possible toward the twelve gauge wire, because you will be using the existing wires to pull the twelve gauge wire through the walls to the breaker box.

Begin pulling the wires from the direction of the breaker box until the new wires appear. Continue to pull them through until the new wires are long enough to extend at least one foot inside the breaker box (don't touch the box while power is on).

At the outlet location, cut the wire at twelve inches from the outlet box, and strip the insulation from the ends. Hook the wires to the outlet (black wire to gold screw, white to silver, and green or copper to green screw. Connect outlet to box and attach cover plate.

Turn off main breaker and attach black and white wires to twenty amp breaker, and green or copper wire to grounding bar inside breaker box. Snap breaker in slot vacated by fifteen amp breaker, and turn on main breaker.

Adding an Additional Line

If your present line serves multiple outlets, you should opt for adding an additional line from your breaker box. While most of the procedures are the same, you will need to feed the wires through walls and ceilings without the assistance of existing wiring.

If the intended location of the new outlet is directly above the breaker box, it shouldn't be too difficult, but if you need to navigate through walls and ceilings, you should consider calling an electrician. Some electrical repairs are best handled by professionals, like RDS Electric.