How do you wire an outside air conditioner?

Wiring the outside condenser unit of an air conditioner is a complex and potentially dangerous task that should be handled by certified electricians or professional HVAC contractors.

There are many benefits of having an air conditioning system in your home or space, the main one being that you get to be in an air-conditioned environment even through very hot temperatures, as air conditioners cool your indoor air.

The installation of some air conditioning systems is quite complex, especially those that need special ductwork and precise wiring for the air conditioner’s internal and external components. Wiring is particularly important, but how is the outdoor part of the air conditioner wired?

Wiring for the air conditioner

An important phase in the process of installing an air conditioning system is the wiring. Connecting the wires accordingly can be the difference between having a working air conditioner and a unit that does not even start, amongst other electrical issues that could arise.

The wiring process is especially delicate and can be dangerous, therefore, it is recommended that you hire a certified electrician who knows how to wire air conditioners correctly and who understands how to handle high and low voltage wires.

So how would they go about wiring an outside AC condenser?

How do you wire an outside air conditioner?

The outside part of the air conditioner that needs to be wired is the condenser. The condenser is one of the most important components of the unit which disperses heat extracted by the evaporator in the home.

The first step is to shut off the power at the circuit breakers and connect the ground wire and high voltage wires.

The high-voltage wires have two insulated power wires (either red and black or black and white each carrying 120 volts of hot current), and one bare copper wire that comes from the disconnect box mounted on an outside wall.

You must connect or insert the ground copper wire to the ground terminal block mounted to the metal panel and secure it by tightening the screw.

Then insert the two high-voltage wires into the high-voltage terminals at the bottom of the contactor (a black box-shaped component that functions as a high-voltage switch).

The screw terminals are tightened to secure the wires and the wires from the disconnect box connect to one end of the contactor.

The low-voltage wires have two individual wire strands inside plastic sheathing. The low-voltage wire set must be pushed into the control box through the access opening of the contactor.

The installer will twist together low-voltage wires from the contactor with the low-voltage wires and secure them with a wire nut, then the ends attach to push fittings on the side of the contactor block.

How the two sets of wires work

The electrician wiring your air conditioner will have two sets of wires with them to connect the condenser unit outside. Both wires are connected to the contactor relay that is inside the condenser unit.

The high-voltage set with a current of 240 volts powers the fan and the compressor of the air conditioner, while the other low-voltage set of wires that run from the thermostat and inside furnace unit turn the condenser on and off. This is how the unit should work upon completion.

Why the wiring of an air conditioner needs to be done professionally

Some air conditioning maintenance and installation can be DIY jobs, but wiring the unit must be done by professional HVAC contractors or licensed electricians.

This is because this job is dangerous and involves the handling of high-voltage components and wiring connections that are not easy to access or easy to identify by someone who is not professionally trained in this regard.

Sometimes refrigerant lines need to be cut and professional soldering work needs to be done.

Different wires and their colours

Air conditioner wires come either as 10/2 or 8/2 wires, or as 10/3 or 8/3 wires. The 10/2/8/2 wire set has a white, black, and copper wire in a cable sheath. The white wire is used as a hot wire and it helps to tape the ends with black tape to signify that it is not neutral.

The 10/3 or 8/3 wire has a white, black, red, and copper wire in a cable sheath. The white wire in this case may not be necessary.

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