What Size Breaker for Mini Split AC? (3 Methods to Calculate)

If you do not choose the correct circuit breaker for your mini-split, you might have several issues. It might trip the breaker or damage the mini-split AC unit. Or you might have a far worse problem, such as an electrical fire. So, to avoid all this, today, I’ll help you figure out which breaker size is most suitable for your mini split air conditioner. Whether you use a small 2-ton mini split AC or a large 5-ton one, this article will help you immensely.

In general, for a 24000 BTU/2-ton mini split unit, you’ll need a 25 amp circuit breaker. For a 36000 BTU/3-ton mini split unit, you’ll need a 30 amp circuit breaker. And, for a large 60000 BTU/5-ton mini split unit, you’ll need a 50 amp circuit breaker.

Read the below article for a more detailed explanation.

How to Determine the Breaker Size for My Mini Split AC Unit?

Mini split AC units are handy for a small room or area because of the ease of use and installation without major central ac and home changes; these devices are popular among most US families. A common question is which breaker is good for the mini split AC unit?

This shouldn’t be complicated. There are three ways to figure out the perfect circuit breaker for your newly brought mini split AC.

• You can use the MAX FUSE and MIN Circuit Ampacity values to determine the breaker size.
• You can use the unit’s max wattage and calculate the breaker size.
• Or use the BTU and EER values to calculate the breaker size.

Method 1 – MAX FUSE and MIN Circuit Ampacity

This method helps determine the breaker size if given the MAX FUSE and MIN Circuit Ampacity values. These values will often be printed on the mini-split AC unit’s data plate. Or refer to the instruction manual.

Before explaining method one properly, you’ll need a good understanding of the MAX FUSE and MIN Circuit Ampacity. So, here’s a simple explanation.

MAX FUSE

The MAX fuse value is the maximum current a mini split AC unit can handle, and you shouldn’t expose the mini split AC unit to more than the MAX FUSE value. For instance, if your AC unit has a MAX FUSE value of 30 amps, it cannot handle more than that. Hence, the dedicated circuit breaker you use shouldn’t exceed 30 amps.

However, this is the max value, and you cannot determine the breaker size entirely based on this. For this, you’ll need the following value too.

MIN Circuit Ampacity

You can use the MIN Circuit Ampacity value to determine the wire gauge and the minimum circuit breaker size for the mini split AC unit.

For instance, if you use an AC unit with a MIN Circuit Ampacity of 20 amps, you should use a 12 AWG wire for the circuit connection. And you cannot use a circuit breaker below 20 amps for this AC unit.

Relationship of the MAX FUSE and MIN Circuit Ampacity

According to the MIN Circuit Ampacity, the MAX FUSE value often exceeds one or two sizes. For instance, if the MIN Circuit Ampacity is 20 amps, the MAX FUSE value should be 25 or 30 amps.

Therefore, if we consider the following mini split AC unit:

MIN Circuit Ampacity = 20 amp

MAX FUSE = 30 amp

You can use the 25 amp or 30 amp circuit breaker for this unit. However, depending on the breaker size, you’ll have to change the wire size.

Circuit Breaker Amp Value	Minimum Wire Size (AWG)
15	14
20	12
30	10
40	8
55	6
70	4

According to the above chart, use 12 or 10 AWG wires for a 25-amp breaker. And for a 30 amp breaker, use only the 10 American Wire Gauge AWG.

Indoor and Outdoor Unit of a Mini Split AC

If you are familiar with a mini split AC unit, you probably know these AC units come with two different parts.

• Outdoor compressor
• Indoor air handling unit

Four cables connect these two parts. Two cables are for the refrigerant flow. One cable is for the flow of electricity. And the last one act as a drain tube.

What to Do If Both Components Have MAX FUSE and MIN Circuit Ampacity Values?

Most probably, indoor and outdoor units have MAX FUSE and MIN Circuit Ampacity values printed on their data plates. And most people get confused about which values to choose to figure out the breaker size. In truth, this confusion is reasonable.

You should always choose the values on the outdoor unit (compressor) since it is the unit that supplies power to the air handling unit.

Method 2 – Max Wattage

This second method focuses on finding the breaker size by using the max wattage. To do that, follow these steps.

Step 1 – Find the Max Wattage

First, look for the max wattage value. It should be printed on the data plate. Or you can find it in the instruction manual. Find a manual specific to your unit online if you cannot find it.

Step 2 – Find the Amperage

Then use Joule’s Law to find the amperage.

According to Joule’s Law,

P = I.V

• P – Wattage
• I – Current
• V – Voltage

Therefore,

I = P/V

Take the P value as 3600W and V as 240V for this example.

I = 3600W/240V

I = 15A

This mini split AC unit draws a maximum of 15A current.

Step 3 – Apply the NEC 80% Rule

After calculating the maximum amperage of the AC unit, apply the NEC 80% rule for circuit breaker safety.

Therefore,

Breaker Size = 15A × 1.2 = 18A

That means a 20 amp breaker is the best option for the above 3600W mini split AC unit. Use a 12 AWG wire for the electrical circuit.

Method 3 – BTU and EER

If you are familiar with air conditioner heat units, you probably know about the BTU and the EER terms. These terms represent British Thermal Unit and Energy Efficiency Ratio.

Apart from that, you can easily locate these values on the mini split AC unit’s data plate or the manual. And these two values are more than enough to calculate the circuit breaker size for your mini-split AC unit. Here’s how you can do that.

Step 1 – Find the Corresponding BTU and EER Values

First, note down the BTU and EER values for your mini split AC unit.

BTU = 36000 BTU

EER = 6 EER

Assume the above values for this demonstration.

Step 2 – Calculate the Max Wattage

Use the following formula to calculate the max wattage.

Max AC Wattage = Capacity (in BTUs)/ EER Rating

Max AC Wattage = 36000 / 6 = 6000W

Step 3 – Calculate the Amperage

After calculating max wattage, use that value to find amperage.

According to Joule’s Law,

P = I.V

• P – Wattage
• I – Current
• V – Voltage

Therefore,

I = P/V

Take the P value as 6000W and V as 240V for this example.

I = 6000W/240V

I = 25A

This mini split AC unit draws a maximum of 25A current.

Step 4 – Apply the NEC 80% Rule

Therefore,

Breaker Size = 25A × 1.2 = 30A

That means a 30 amp breaker is the best option for the above 36000 BTU mini split AC unit. Use a 10 AWG wire for the electrical circuit.

Important: The above results may vary depending on your mini split AC unit’s EER value, voltage, and BTU value. So, ensure to complete the calculation accordingly.

Which Method is Best for Finding the Breaker Size?

In truth, all three methods are excellent for figuring out the correct breaker size for your mini split AC unit. But you’ve to be a little careful while completing the calculation part. One wrong step might be devastating. It could fry the AC unit’s circuit. Or it might start an electrical fire.

And if you can use at least two methods for the same unit, it will be safer. Also, if you are uncomfortable following such tasks, remember to get help from a qualified professional.

Top 5 Zone

Benjamin Sahlstrom

Ty Branaman