How To Upgrade Your Electric Circuit When You Switch To A Larger Air Conditioner

If you were still uncomfortable during the last heat wave even though your old window air conditioner was running at full capacity, it's time to get a newer unit. However, your old 15 amp circuit may be inadequate for the kind of power consumption a large unit may require.

This is particularly an issue whenever the compressor kicks on, and additional power is required. Even if the circuit is a dedicated line, which means the the circuit serves only the outlet for your air conditioner, a 15 amp line may not be enough.

Of course, you can plug in a larger unit and give it a try. If your breaker shuts off when the compressor turns on, then it's time for an upgrade to a 20 amp line.

What do you need to switch to a 20 amp line?

20 amp circuit breaker

Buy a breaker that is made by the manufacturer of your breaker box or it may not fit inside the slots in the box. 

A three wire sheath of 12 gauge wire

You must use at least 12 gauge wire for a 20 amp circuit. If you attempt to save money by reusing the 14 gauge wire that is already installed in your old 15 amp line, you run the risk of overheating and fire.

A fifty foot roll of 12 gauge wire should be sufficient. It will be marked "12-2", which indicates that the sheath includes both a neutral and a ground wire in addition to the hot wire.

Wire stripper/cutter tool.

Electrical tape

Screwdrivers (flat and philips head)


Disconnecting the circuit line from the breaker box

You will disconnect the existing wiring from the breaker box because you will use it to pull the 12 gauge wire from the box through the walls to the outlet. Working inside the breaker box requires turning off the main breakers to the home.

The main breakers may be located at the top of the breaker box or in another location. When the mains are shut down, you will remove the breaker box cover panel by removing the screws that secure it.

You will then remove the 15 amp breaker that controls power to the outlet by pulling it from its slot in the box..Pull it from the outer edge, with the black hot wire attached,for easiest extraction.

You will then disconnect the black wire by loosening the terminal screw, then disconnect the white and green wires that enter the breaker box at the same point as the black wire by loosening the screws on the white  grounding bars to which they are connected.

Pulling the 12 gauge wire to the outlet

When all three wires are disconnected, you will strip 3/4" of insulation from the ends of each of the three wires in the 12 gauge sheath. Twist these wire ends with the recently disconnected wire ends, then wrap the twisted wire ends in electrical tape to secure them together.

You will then go to the outlet location, remove the cover plate from the outlet, then loosen the two screws that hold the outlet inside the gang box in the wall. Pull the outlet from the wall and disconnect the wires by loosening the terminal screws.

You will then grasp the wires and begin to pull them through the walls until the taped wire ends appear. Pull the taped ends until they protrude to a length of six inches from the outlet.

Connecting the new wires to the outlet

After removing the electrical tape and separating the wires, you will connect the black 12 gauge wire to the top brass terminal of the outlet by looping it in a clockwise direction under the terminal screw. Tighten the screw fully until the wire is secure.

You will then connect the white wire to the top silver terminal and the green wire to the single green terminal in the same manner. Push the outlet into the gang box, tighten the securing screws, and replace the outlet cover plate.

Connecting the outlet to the breaker box

Cut the sheath of 12 gauge wire at a point that is 12" from the point of entry at the side of the box, then strip the wire ends in the same manner as before. You will them connect the black wire to the screw terminal on the new 20 amp breaker and push the breaker into the slot vacated by the old 15 amp breaker. The breaker will click into place when fully seated in the slot.

You will then insert the white and green wire ends into any available openings in the white grounding posts, then tighten the securing screws.

Replace the cover panel of the breaker box, then turn on the main breakers.

Flip on the new 20 amp breaker, then turn on your AC, crank it up to full power, grab a drink, and relax.. You deserve a cold drink in a cool room for all of your hard work. For more information or assistance, contact companies like Conway Electric.