Things You'll Need
Adjustable open-end pliers
Installing an A/C disconnect switch is a good idea for safety reasons, and it is required by code. Disconnects provide a way of removing power from the air conditioning unit for servicing. There are two styles used in residential homes. There are non-fused and fused disconnects. Both types connect to the power and the unit the same way. The enclosure is made of either metal or plastic. Disconnects for air conditioners are usually located outside. This is because the disconnecting means is required to be within sight of the unit.
Turn off the breaker for the air conditioning unit or turn off the main breaker. Verify with the voltmeter that the power is off. Find a location to mount the disconnect switch. Determine which direction the wires will enter the disconnect enclosure from the source.
Remove the knockouts for both the incoming power and the outgoing wires to the unit. Push the knockout tab with the screwdriver, grab it with the pliers and rock it back and forth until it breaks away.
Insert the wires into the disconnect switch. Place it on the wall at the desired location. Use the level and wall anchors to secure it to the wall. Keep it level while tightening the screws.
Strip the insulation using the wire strippers. Do this on all three wires about ½-inch. This may be one black wire and one red wire with one green, or two black wires and a green wire. The black/red wires are the hot wires, and green is the ground wire.
Insert the wires into the lugs on the disconnect switch and tighten so they are snug. Follow the manufacturer's instructions as to where to attach the wires.
Remove the lock nut from the connector on the flexible conduit attached to the air conditioner unit. Insert the connector into the disconnect switch. Slip the lock nut over the wires and tighten snugly, using the adjustable pliers.
Strip the wires from the unit and attach the wires to the lugs on the disconnect switch.
Close the cover on the disconnect switch. Turn on the power. Check that the disconnect switch works correctly.
If the air conditioning unit requires fuses, that information is located on the nameplate along with the maximum amperage draw.
Any time you are working on or around electricity, you should turn off all sources of power before beginning work. Electricity can cause severe injury or death if handled improperly.