If you’re getting a mini split but wonder if you need to upgrade your breaker size, I’ve surveyed the running current (amp) of various mini split sizes, types and efficiencies to come out with a range that could help you make a decision.
Without further ado, here is the range of amps of a single 230V mini split unit draws:
|Mini Split BTU
|2.5 – 4.2 A
|3.8 – 6.0 A
|4.8 – 5.4 A
|6.1 – 9.1 A
|7.9 – 11.7 A
|10.6 – 13.8 A
|14.0 – 20.9 A
|16.0 – 16.1 A
|16.7 – 24.4 A
In most cases, the above amps should fall within the range needed for breaker and other electrical sizing. But, if you want to have more conviction, I provided the details and factors that affect the running amps in the following.
Which Mini Split Amps to Use: Rated or Maximum?
The specification we see on mini split brochures, catalogs and performance sheets is based on the rated conditions. Hence, the stated current is known as rated current or running current.
Rated current is the electrical current which the mini split is operating at rated conditions where:
- Indoor temperature is 80°FDB, 67°FWB for cooling and 70°FDB, 60°FWB for heating
- Outdoor temperature is 95°FDB, 75°FWB for cooling and 47°FDB, 43°FWB for heating
However, a mini split can draw less/more amps if the operating conditions change.
For instance, if the outdoor temperature is high, the mini split will draw more power and thus, more amps. Another example is when the indoor temperature is high, the mini split will draw more amps as well (although less significant compared to outdoor temperature).
So, relying on the rated current is risky. On hot days, your mini split may draw more amps than you anticipate which can cause your breaker to trip.
Therefore, using the maximum current to size the circuit breaker is the preferred method.
Mini split manufacturers provide their recommended breaker size in their installation manuals which typically look like this:
When sizing the wire, we should always refer to the MCA (minimum circuit amp). For the circuit breaker size, we must refer to the MFA (maximum fuse amp). The manufacturer had already accounted for the worst possible case scenario when making these recommendations.
Once you know what size breaker and wire you need, you may also want to know how to wire a mini split from your house main breaker to the disconnect switch and then the mini split. If that’s something you need to know, I encourage you check out my comprehensive guide.
115V Mini Splits Draw Higher Amps
The rule of electrical says if the voltage is reduced, the ampere must increase to deliver the same power (P=IV). While 115V mini splits are more convenient to install, they draw much more amps than mini splits that use 230V.
Here are the differences:
|Mini Split BTU
|115V Mini Split
|230V Mini Split
|average ~ 7.1 A
|average ~ 3.0 A
|average ~ 10.5 A
|average ~ 4.4 A
As we can see, the difference is staggering. A 115V mini split draws more than twice the amount of amps of a 230V mini split. Thus, given the same capacity, the 115V model often requires a circuit breaker one size bigger than the 230V model.
High SEER Mini Splits Draw Less Amps
Throughout my research, I noticed that the higher the efficiency of a mini split, the less amps it draws given the same BTU (capacity). This is not hard to understand as high-efficient mini splits use less power to achieve the same result.
For instance, a 16 SEER mini split with 12000 BTU of cooling capacity draws 5.5A (rated current). In comparison, two 23 SEER mini splits with the same capacity draw an average of 4.3A (rated current) which is about 22% less.
In practice, this amps draw increase is not significant enough to change the breaker and wire size under most circumstances. However, there is an exception.
Mini splits have a wide range of efficiency rating. Some have the highest SEER rating you’ve ever see. Check out the list of most efficient mini split I put together. You may potentially find one that suits your needs.
Cold Climate Mini Splits Draw Significantly More Amps
Mini splits designed for cold weather usually have very high SEER value. Although higher SEER means lower amps draw, the extended heating performance these cold-climate mini splits provide is what contributes to higher amps draw.
The 18000 BTU standard model has an MCA and MFA of 15A and 20A respectively. Meanwhile, the cold-climate model with the same capacity has an MCA and MFA of 18A and 25A respectively.
This means if you were to use the cold-climate model, you need a 25A breaker instead of a 20A. Not to mention, if you add on the optional drain pan heater (freeze prevention), the total amps draw increase further.
So, we need to be very careful with the amps draw when choosing a cold climate mini split.
Many complains about mini split unable to provide sufficient heating are associated with choosing the wrong model. I’ve put together a list of best mini splits for heating in cold climates. I encourage you to read it if you’re looking to get one.
Mini Split Compressor, Indoor & Outdoor Amps Draw
Other than the overall system amps draw as I outlined above, mini split amps draw is also separated into 3 different components: a) compressor motor, b) indoor fan motor and c) outdoor fan motor.
The compressor of a mini split draws the most amps (e.g.: 12A). It is typically written as RLA which stands for rated load amps, meaning the maximum current that comes in the cooling and heating operation.
The fan motor of the indoor and outdoor units of a mini split draws a relatively small amount of amps (e.g.: 0.3A) which is typically written as FLA or full load amps. As the name suggests, it is the highest possible amps draw of the fan motor.
Regardless of the compressor RLA and the fan motor FLA, the circuit breaker of a mini split should always be sized based on the MFA or maximum fuse amps and the wire of a mini split should always be sized based on the circuit breaker size plus the MCA or minimum circuit amps.
Mini Split Compressor Starting Amps
Sometimes, the nameplate of the outdoor unit of a mini split may have the LRA or locked rotor amps written on it. However, we don’t size circuit breakers based on the LRA.
LRA is the electrical current (amps) needed to spin a standstill motor. So, it’s basically the starting current of the compressor. As the compressor starts spinning, the current drops.
The starting current (or starting amps) is usually much higher than the running amps. However, we don’t size the circuit breaker based on LRA because a standard thermal-magnetic circuit breaker allows high amps to pass through momentarily (about 10 seconds) and this is completely normal.
Circuit Breaker or Time Delay Fuse for Mini Splits?
When choosing a circuit breaker, we may come across a mini split that says: “use a time delay fuse”. So, what’s that and should you use a circuit breaker or a fuse?
Mini splits have a few motors and motors naturally have a surge of power during startup (the starting amps I mentioned earlier). Hence, a normal fuse that breaks at the instant of an overload cannot be used.
Instead, we need to use a fuse that has a time delay function. Basically, a time delay fuse is like a thermal-magnetic circuit breaker. It does not trip during startup when there is a high starting amp.
Lastly, consider my Mini Split (eBook) if you want to know how can you use Mini Split in your house. If you still have doubt or not feeling confident enough, feel free to consult me.
Ask me for HVAC advice such as brand selection, best model, benefits, features, placement, duct size, grille size, how to design, design check, verification and other HVAC related queries.