How To Wire An AC Unit? Step By Step Tutorial With Diagram

How To Wire An AC Unit

Wiring an AC unit can be pretty difficult if you don’t know what you’re doing or if you have a little bit of knowledge. 

And let me tell you something that wiring an ac unit is a pretty easy task once you get used to it. There are not that many parts involved in wiring. So once you learn the wiring setup of few items you can easily wire the whole unit.  

So In this article, I’ll explain how to wire ac unit with the help of a diagram. 

Before touching any wires make sure you disconnect the power to the ac unit. Because it can be fatal if you operate an ac unit while the power is running.

Also, make sure to discharge the capacitor because it also stores charge and it’ll not harm you that much but it is capable of giving you a good shock.

Note: In the above diagram, the wires are not hotwired and overlapping.

1. Wiring between Disconnect Switch to Contactor:

How To Wire An AC Unit

Starting with the 240V power supply coming from disconnect a lot of times it’ll be a red and a black wire along with the green wire that is in there.

And you got your disconnect that’s probably gonna be mounted to the side of the house it’ll either be a lever or breaker type.

Basically, you have 240 volts coming from your circuit breaker panel it’s your disconnect from the house and then from there, it goes through the electrical whip and into the contactor.

So this electrical whip will have three wires usually they’re gonna be black red green. The black wire will go to one side of the contactor then we got a red wire that will go to the other side of the contactor.

And then we have ground wire just gonna be a green that will just be mounted to the chassis. The condenser unit will have a little square screw-like strap that you put the ground wire into.

So now we have our main power supply hooked up each of the power wires is 120 volts to give us 240 volts. Those two wires are hooked up to the contactor on the L1 and L2. 

2.Wiring between compressor-capacitor-contactor:

How To Wire An AC Unit

Next, we’re wiring up our compressor. The compressor will have three wires coming out of it a wire coming from the common, the run, and the start windings. And remember that the start winding always goes to the run capacitor.

So if you have a dual run capacitor the start winding will always be the one that is connected to the HERM section. The other two wires the run and the common will go on either side of the contactor.

3. Wiring Condenser Fan- Contactor-Capacitor

How To Wire An AC Unit

Now next up is the condenser fan motor and a lot of them will be three-wire fan motors. Once again just like the compressor one wire which is typically either brown or purple will go to the fan section on the dual run capacitor.

And the other two wires have to go on either side of the contactor. And if possible I like to keep the wire colors on the same side of the contactor. 

The wire from common on the dual run capacitor will go to the same place as the wire coming from the run winding and the compressor.

Check Out Contactor Not Pulling In Problem Solved

4. Thermostat to contactor wiring

Last but not least we got the 24 volts coming from inside the house. And if you have a furnace hooked up like I do what that would look like is you’ll typically have a 2 thermostat wire running from inside of the house and going out to your unit and hooking up to the contactor coil. 

In the above figure, those wires are blue and brown ones on the right side.

Check Out Thermostat Wiring Explained Click Here

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