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What Size Breaker Do I Need for a Mini Split? – Answered

Writen by Edwin Jones

Fact checked by Andrew Wright

what size breaker do i need for a mini split

I’ve had a handful of customers ask me, “What size breaker do I need for a mini split?” I almost always say I can’t answer without knowing the BTU capacity. Mini split voltage plays a bit of a role, too, since 220V circuits commonly need bigger wires than 110V.

When in doubt, refer to the heat pump or AC’s Max Fuse recommendations while being mindful of the Minimum Circuit Ampacity. The breaker and wire size you choose should ideally be within the range of both.

Continue reading for a more in-depth answer.

Size Breaker for Mini Split AC

mini-split-breaker-size

If you can find the manufacturer’s label or nameplate on the mini split appliance, you can always get the most reliable electrical recommendations.

1. Find the Max Fuse amperage

Unsure about following the Max Fuse (aka Max Overcurrent Protection) figure? Don’t worry, this specified value is suitable for both breakers and fuses.

Moreover, since it’s specifically stated as the maximum limit, you can’t go over that. And, yes, you need to do this even if the Code states that you can upgrade to the next breaker size.

2. Consider the Minimum Circuit Ampacity Breaker Size

Can you go for lower breaker sizes? As long as you don’t end up with a size that’s smaller than the Minimum Circuit Ampacity (which could potentially lead to overheating issues), then yes.

For example, if the MCA is 20A, the breaker should at least have this amperage value, which already factors in 125% of the compressor.

Most units have maximum fuse values that are often one or two sizes larger than the MCA while remaining entirely Code-compliant. In the case of the unit mentioned above (20A MCA with 25A max fuse), expect 25-amp and 20-amp time delay breakers to do just fine.

Alternatively,

  • You may have a 110V 12,000 BTU mini split, which requires a 15-amp breaker at least and a 12-gauge wire as per recommendations. Similarly, a 9,000 BTU unit should go with a 15A breaker.
  • On the other hand, a larger 220V 18,000 BTU unit works best with an 18-amp CB with 10-gauge wire.
  • Finally, a 220V 27,000 BTU pump may call for a 35-amp breaker or 25-amp breaker.

What if the Indoor Unit and Outdoor Unit Show Different Mca and Max Fuse Values?

minimum-circuit-ampacity-breaker-size

Let’s assume that upon checking the stickers of both, you see that the outdoor unit has an MCA of 20A and Max Fuse of 30A, while the indoor unit has an MCA of 5A and Max Fuse of 20A.

Understandably, this creates a lot of confusion among property owners. Mostly, it’s the outdoor unit’s labels that you should be paying more attention to as most mini split systems have it powering the indoor unit from outside your home or office.

Breaker and Wire Sizes

If you need to upsize your breaker and it requires a larger wire, then you need to change your wire as well.

On the bright side, larger wire sizes tend to generate less heat than their smaller counterparts, which happen to be less taxing on the compressor, too. Essentially, that means you’ll be spared overheating problems with long-term use.

Again, please read the label or nameplate as it will save you from plenty of headaches. It doesn’t matter whether the unit is manufactured by MrCool, Klimaire, Carrier, Mitsubishi, etc., or if it’s ductless or not.

If it’s no longer readable, contact the manufacturer directly and state the specific model series of your unit.

Don’t forget about checking the included installation manual, as it may contain meaningful electrical information. The same goes for using charts as your reference when pairing the circuit breaker with the right wire.

Here’s my own detailed breakdown to help you out more in seeing the relationship between voltage, breaker size, and wire size:

BTU Breaker Wire Size Voltage
9,000 15A 12-Gauge 110V
12,000 20A 12-Gauge 110V
18,000 20A 10-Gauge 220V
24,000 25A 10-Gauge 220V

Better yet, just let an electrician handle the entire circuit breaker installation for you, especially if you’re still getting confused by Maximum Circuit Ampacity and Max Fuse values when figuring out mini split breaker size.

Conclusion

To wrap everything up, you first need to determine your unit’s precise power requirements to know the correct answer to, “What size breaker do I need for a mini split?” Acquiring this information shouldn’t be needlessly complicated if you know where to look (i.e. the nameplate, label, or instruction manual).

If you’re still not sure, but want to still go ahead with your electrical project, you can consult an electrician, who will give you the exact wire and breaker sizes needed for your mini split.

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