Every air conditioner has to be wired. Choosing the wrong wire size for your AC unit will fry the circuit (and possibly damage the unit itself). Everybody knows they need the correct air conditioner wire size; not everybody knows what is the correct AC wire size, however.
To help you out choosing an adequate wire size, we are going to look at how to calculate the wire size for an air conditioner.
Example: Let’s say you have a 3-ton AC unit that runs on a 220V circuit. What size wire do you need for this 2-ton unit?
- First, we need to calculate the wattage (3-ton units, on average, have a max. wattage of 3,600W).
- Then we calculate the amps (3,600W/220V = 16.36A).
- We also have to account for the 80% NEC rule (10.91A × 1.25 = 20.45A); this is the minimum ampacity of a wire we need.
- Choose the wire size based on the minimum ampacity. 12 AWG wire has 20A ampacity; it’s too small. 10 AWG wire has 25A ampacity (above the required minimum of 20.45A). That means that we need to use a 10 AWG wire (or larger) for a 3-ton air conditioner.
We will explain how you can do this calculator for any air conditioner capacity. On top of that, you can use 2 resources that will help you adequately estimate the air conditioner wire size, namely:
- Air Conditioner Wire Size Calculator. You just input the AC capacity (tonnage) and the circuit voltage (Example: 220V), and the calculator outputs the minimum wire ampacity you need. Based on this, you can choose the correct AWG gauge wire size.
- Air Conditioner Wire Size Chart. This is a chart with pre-calculated wattages for 0.75-ton to 6-ton AC units, minimum ampacity, and the corresponding AC wire sizes you can use to wire an air conditioner.
Before you check the calculator and the chart, however, it’s quite useful to look at what the air conditioner wire size calculation looks like:
How To Calculate Wire Size For An Air Conditioner?
Usually, the only thing we know about our air conditioner is the tonnage and the voltage. We have 1-ton, 2-ton, 3-ton, 4-ton AC units, and so on, that run on 220V circuit (smaller below 1.5-ton units run on 110/120V circuits). This is actually all the information we need to calculate the wire size.
How to get from the AC tonnage to the AWG gauge wire choice?
Here is a 4 step-by-step guide on how you calculate the wire size for an air conditioner:
- Calculate the max. AC wattage (based on tonnage; you can also find the max. wattage of the specs sheet). Here we presume that all AC units have a 10 EER rating (most have a bit higher EER rating but by using a 10 EER rating we approximately account for the voltage drop as well). That means that a 3-ton AC unit (36,000 BTU) has a max. wattage of 3,600W. Similarly, a 2-ton unit (24,000 BTU) has a max. wattage of 2,400W. The equation for calculating the max. AC wattage based on tonnage and EER rating looks like this:
AC Max. Wattage = BTU Capacity / EER Rating
Here you have to keep in mind that 1 ton is equal to 12,000 BTU (these are British Thermal Units).
- Based on the max. wattage, calculate the amps. You will have to use voltage here. Amps the AC will draw at 100% output are calculated by dividing max. wattage by the voltage. Example: A 2-ton AC unit has a max. wattage of 2,400W and it runs on 220V. That means the amp draw will be 2,400W/220V = 10.91A. Here is the equation for AC amp draw:
AC Amp Draw = Max. Wattage / Voltage
- Account for 80% NEC rule. This is a National Electric Code rule that states that the AC amp draw can account for at most 80% of the total ampacity of the wire you are using. To account for this, you have to multiply the AC amp draw by a 1.25 factor. Example: 2-ton AC unit draws 10.91A of current. This amount of current should represent at most 80% of the total wire ampacity. If you multiply 10.91A by 1.25 you get the minimum required AC wire amps: 13.64A.
- When you have the min. required amps, you have to consult this AWG gauge wire amps chart to check for which wires have high enough ampacity. If you need at least 13.64A ampacity, you go with an 18 AWG wire because it has a 14A ampacity.
This whole process can be quite lengthy. To shorten it and automatically determine the amps you need for air conditioner wiring, you can use this simple calculator that does all these calculations automatically:
Air Conditioner Wire Size Calculator
You just input the AC tonnage and the circuit voltage, and the calculator will output how many amps (minimum) should the AC wire handle (minimum ampacity):
Here is how you can use this AC wire size calculator:
Let’s say that we have a 2.5-ton AC unit that runs on 220V. You just slide the AC tonnage to ‘2.5’ and slide the voltage to ‘220’. You will see that the minimum ampacity your AC wire should handle is 17.05 amps.
This is the key information you need. Now you can consult the AWG wire size chart and check for the wires with more than 17.05A ampacity. 16 AWG wire, for example, has a 17A ampacity; it’s just a bit too small. The correct wire size for this 2.5-ton AC unit is the 14 AWG with 20A ampacity.
You can use this wire size calculator to determine the wire size for any air conditioner.
Or, if you don’t like to do it manually, you can consult this pre-calculated air conditioner wire size chart:
Air Conditioner Wire Size Chart (1.5-5 Ton Units)
|Air Conditioner Tonnage:||Max. Wattage (At 10 EER):||Amp Draw At 220V:||Min. Wire Ampacity:||Min. Wire Size:|
|1.5 Ton||1,800 Watts||8.18 Amps||10.23 Amps||18 AWG Wire|
|2 Ton||2,400 Watts||10.91 Amps||13.64 Amps||18 AWG Wire|
|2.5 Ton||3,000 Watts||13.64 Amps||17.05 Amps||14 AWG Wire|
|3 Ton||3,600 Watts||16.36 Amps||20.45 Amps||12 AWG Wire|
|3.5 Ton||4,200 Watts||19.09 Amps||23.86 Amps||12 AWG Wire|
|4 Ton||4,800 Watts||21.82 Amps||27.28 Amps||10 AWG Wire|
|4.5 Ton||5,400 Watts||24.55 Amps||30.69 Amps||10 AWG Wire|
|5 Ton||6,000 Watts||27.27 Amps||34.09 Amps||10 AWG Wire|
As we can see, most air conditioner requires anywhere from 18 AWG to 10 AWG wires. Bigger 5+ ton AC units require even thicker wires; 8 AWG or even 6 AWG.
Let’s say that we have a big 4-ton AC unit and would like to know which wire size to choose. An average 4-ton AC unit has a max. wattage of about 4,800W and requires a wire with a minimum ampacity of 27.28A. That means you will need to use a 10 AWG wire with 35A ampacity.
You can get all this AC wire sizing information from this chart.
We hope this helps. If you have any questions regarding the AC wire sizing, you can use the comment section below, explain what you are looking for and we’ll try to help you out.
Choosing the right AC size wire usually goes hand in hand with choosing the right AC breaker size. You can check this article about AC breaker sizes for more help.