Central AC Power Requirements (With Wire Size and Break Size)

This central air conditioner wiring guide is designed to help you choose the correct wiring to run from your indoor power panel to where the outdoor disconnect box will be installed. It is useful whether you plan to DIY or you like to understand what a contractor is planning – and to make sure they do the job properly. 

Convenient wire capacity and size charts are provided, so you can easily find both the circuit breaker and wire size for your particular air conditioning system. Some FAQ’s will also be found at the end of this article addressing wiring size. 

Supplies Needed for Central AC Wiring

Starting at the main power panel, you will need the following electrical supplies:

1. A “double pole” circuit breaker (220v) of the appropriate brand for the breaker box and the correct amperage for the central AC system.

Supplies tips: Not every circuit breaker will fit in every breaker box. Check your AC’s installation manual or talk with an electrician to determine the right breaker at the right amps.

2. Electrical wire, commonly called Romex, of the correct size for the AC system and long enough to run from the power panel to the location where the condenser will be located.

Info tip: Common central air conditioner wire size options are discussed below.

3.  A disconnect box to be mounted outside the house within a few feet of the condenser location. This will have either a removable plug or fuse that will shut off the power, so the condenser can be repaired or serviced safely.

4. Another short section of electrical wire to run from the disconnect box to the condenser. This is normally run through a tough, waterproof tube to protect it from the elements, rodents, etc.

Buying tip: Ready-made electrical whips are available to run from the disconnect box to the condenser. Installers use them to save time, which will save you money.

5. An additional set of low voltage wires from the AC condenser to the control board on the home’s furnace will also be needed. A signal from the thermostat is sent through these wires to call for the AC system to turn on and off. 

Central Air Conditioner Power and Wire Requirements 

A central air conditioning system requires a 220-volt circuit of its own. These systems are large users of electricity. When most central air conditioners first start up, they may require up to 5,000 watts of electricity. This is about 4 to 5 times that of an electric hair dryer. Some of that power is supplied by the battery-like capacitor. But a lot of it has to come straight from the wiring.

Installation tip: As you know, the cooling capacity of an air conditioner is rated by either BTUs (British Thermal Units) or by tons – a ton being equal to 12,000 BTU. The more BTUs or tons, the more cooling power the air conditioner has. But this also means that it will require more electrical power. So be sure to use the wiring and circuit breakers appropriate for the system, especially if you are a DIYer. 

What Size Circuit Breaker for Central Air Conditioner? 

You can use a breaker with more capacity than you need, of course. 

What size breaker for a central air conditioner?

Cooling CapacityCooling Capacity BtuCircuit Breaker Size
1.5 Ton18,000 Btu15 Amp
2 Ton24,000 Btu15 Amp
2.5 Ton30,000 Btu15 Amp
3 Ton36,000 Btu15 Amp
3.5 Ton42,000 Btu20 Amp
4 Ton48,000 Btu20 Amp
5 Ton60,000 Btu30 Amp

How many amp breaker for 2 ton AC?

Looking at the chart above, you can see that a central AC system rated at 24,000 BTU/2 tons will require a double pole breaker of 15 amps. 

What size breaker for 4 ton AC? 

Scrolling down the chart, a system that is rated at 48,000 BTU/4 tons will need a 20 amp breaker. It will be a double pole breaker. 

Info tip: At the circuit breaker box, the important issue of preventing damage to the wiring and the system in general is addressed. This is the job of the circuit breaker. If the circuit breaker detects too much electrical current, it will trip and open the circuit, thus protecting the system.  

What Size Wire for Central Air Conditioner?

Gauge size – In wire, as you likely know, the smaller the number, the thicker the wire. For some, that’s a new idea that takes a little getting used to.

What size wire for a central air conditioner?

Cooling CapacityCooling Capacity BtuWire Size
1.5 Ton18,000 Btu14  Gauge
2 Ton24,000 Btu14  Gauge
2.5 Ton30,000 Btu14  Gauge
3 Ton36,000 Btu14  Gauge
3.5 Ton42,000 Btu12  Gauge
4 Ton48,000 Btu12  Gauge
5 Ton60,000 Btu10  Gauge

What size wire for 2 ton air conditioner?

14 gauge. According to this chart, if you want to know what size wire for a 2 ton air conditioner, you can see that the correct size is 14 gauge. The BTU ratings are also listed here, if that is how you are trying to determine the wiring size.

What size wire for 30 amp air conditioner?

10 gauge wire. How do we reach that conclusion? These two charts can also be used together. For example, if your question is what size wire for a 30 amp air conditioner, look at the first chart to see that a 30 amp AC unit is one that is rated at 5 tons (60,000 BTU). Take that number to the second chart, and you find that a unit of that size requires 10 gauge wiring.

Should I use 10/2 or 10/3 wire for a central air conditioner? 

10/2 is the recommended wire size and type to use for a large central air conditioner. The designation, 10/2, 12/2, 14/2 and so forth, indicate that it is to be used for a 2 wire circuit, like the majority of residential circuits. 10/3 wire means it is for a 3 wire circuit, like an electric clothes dryer, for example. 

Central Air Conditioner Wiring FAQ’s

Will 10-2 wires work on the central air conditioner? 

Yes, but 10 gauge wire (sometimes mis-written as 10 gage wire) is only required on the larger size central air conditioners because it will handle more current (amps). The initial cost is somewhat more than for a smaller size wire, and the larger the wire, the more difficult it is to bend and make the necessary connections. 

What size wire for 230 volt air conditioner? 

The correct wire size for any central air conditioner is not determined by voltages, but by the cooling capacity of the system. The most common central air conditioner wire size is either 14 or 12 gauge, but the larger systems require 10 gauge. Find the wire size you need on the charts above.

Concerning supplies for this job, are there any others I will need in addition to those listed above? 

Yes. At the main breaker panel, you will want a cable clamp to secure the wire where it enters the box. You will also want to get some electrical staples to secure the wire to the wood framing along its length from the main panel to where it passes through to the disconnect box. Talk to your supplier for additional help, so you will not have to return for more supplies. 

Final Note 

The wire sizes and recommended amperages in this article are all based on general installation practices and codes. Some local regulations may be different, including that all electrical work must be performed by a licensed electrician. 

Be sure to consult the local regulations or building codes before you begin installation.

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.

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