What is the size of the switch for AC mini split system? (3 calculation methods)
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If you don't choose the right circuit breaker for your mini split, you may run into a few problems. Doing so may trip the breaker or damage the mini AC unit. Or you may have a much more serious problem, such as an electrical fire. So, to avoid all this, today I will help you figure out what size breaker is best for your mini split air conditioner. Whether you are using a small 2 ton mini split air conditioner or a large 5 ton one, this article will help you a lot.
Typically, for a 24000 BTU/2 ton mini split unit, you will need a 25 amp circuit breaker. For a 36000 BTU/3 ton mini split unit, you will need a 30 amp circuit breaker. And for a large 60000 5 BTU/50 ton split unit, you will need a XNUMX amp circuit breaker.
Read the article below for a more detailed explanation.
How do I determine the switch size for my AC mini split unit?
Mini split system units are convenient for a small room or area due to the ease of use and installation without significant changes to the central air conditioner and home; these devices are popular among most American families. A common question is which switch is suitable for a mini split AC unit?
It shouldn't be difficult. There are three ways to find the perfect circuit breaker for your new mini AC split system.
- You can use the MAX FUSE and MIN Circuit Ampacity values to determine the switch size.
- You can use the maximum power of the device and calculate the size of the switch.
- Or use the BTU and EER values to calculate the breaker size.
Method 1 - MAX. FUSE and MIN. circuit current
This method helps to determine the breaker size when MAX FUSE and MIN Circuit Ampacity are set. These values are often printed on the nameplate of a mini split air conditioner. Or refer to the instruction manual.
Before you can properly explain the first method, you need to have a good understanding of MAX. FUSE and MIN. circuit current. So here's a simple explanation.
MAXIMUM FUSE
The MAX fuse value is the maximum current that the AC mini split unit can handle, and you should not expose the AC mini split unit to more than the MAX FUSE value. For example, if your AC unit has a MAX FUSE rating of 30 amps, it cannot handle more than that. Therefore, the dedicated circuit breaker you use should not exceed 30 amps.
However, this is the maximum value and you cannot fully size the switch based on it. You will also need the following value for this.
MIN. circuit power
You can use the MIN Circuit Ampacity value to determine the wire gauge and minimum circuit breaker size for a split mini AC unit.
For example, if you are using an AC unit with a minimum circuit current of 20 amps, you should use 12 AWG wire to connect the circuit. And you cannot use a circuit breaker below 20 amps for this AC unit.
Relationship MAX. FUSE and MIN. circuit current
According to the MINIMUM ampacity of the circuit, the MAX. FUSE often exceeds one or two sizes. For example, if MIN. circuit current is 20 amps, MAX value. FUSE should be 25 or 30 amps.
So if we consider the following mini AC split unit:
A 25 or 30 amp circuit breaker can be used for this device. However, depending on the size of the switch, you will need to resize the wire.
| Circuit breaker current value | Minimum wire size (AWG) |
| 15 | 14 |
| 20 | 12 |
| 30 | 10 |
| 40 | 8 |
| 55 | 6 |
| 70 | 4 |
According to the table above, use 12 or 10 AWG wire for a 25 amp circuit breaker. And for a 30 amp breaker, use only AWG 10 American Wire Gauge.
Indoor and outdoor mini split air conditioning unit
If you are familiar with mini split AC unit, you probably know that these AC units are made up of two different parts.
- Outdoor compressor
- Indoor air handling unit
Four cables connect these two parts. Two cables are provided for the refrigerant supply. One cable is for supplying electricity. And the latter acts as a drainage tube.
What if both components have MAX FUSE and MIN circuit current values?
Most likely, the MAX FUSE and MIN Circuit Ampacity values are printed on the nameplates of the indoor and outdoor units. And most people get confused about which values to choose for sizing a switch. In truth, this confusion is reasonable.
The outdoor unit (compressor) should always be selected as it supplies power to the air handling unit.
Method 2 - maximum power
This second method aims to size the circuit breaker using maximum power. To do this, follow these steps.
Step 1 - Find the maximum power
First, find the maximum power value. It must be printed on the rating plate. Or you can find it in the instruction manual. If you can't find it, search the web for a manual related to your device.
Step 2 - Find the current
Then use Joule's law to find the current.
According to Joule's law,
- P - power
- I am current
- V - voltage
Consequently, the
Take P as 3600W and V as 240V for this example.
This mini AC unit draws no more than 15A.
Step 3: Apply the NEC 80% Rule
After calculating the maximum AC unit current, apply the NEC 80% rule for circuit breaker safety.
Consequently, the
This means that a 20 amp breaker is the best option for the aforementioned 3600W mini AC unit. Use 12 AWG wire for the electrical circuit.
Method 3 - BTU and EER
If you are familiar with air conditioner thermal units, you are probably familiar with the terms BTU and EER. These terms are British Thermal Unit and Energy Efficiency Ratio.
Also, you can easily find these values on the nameplate of the mini split unit or in the manual. And these two values are more than enough to calculate the circuit breaker rating for your mini AC split unit. Here is how you can do it.
Step 1. Find the appropriate BTU and EER values.
First, write down the BTU and EER values for your mini AC unit.
Accept the above values for this demo.
Step 2 - Calculate the maximum power
Use the following formula to calculate the maximum power.
Step 3 - Calculate the current
After calculating the maximum power, use this value to determine the current strength.
According to Joule's law,
- P - power
- I am current
- V - voltage
Consequently, the
Take P as 6000W and V as 240V for this example.
This mini AC unit draws no more than 25A.
Step 4: Apply the NEC 80% Rule
Consequently, the
This means that a 30 amp breaker is the best option for the aforementioned 36000 BTU mini AC unit. Use 10 AWG wire for the electrical circuit.
important: The above results may vary depending on the EER value, voltage and BTU value of your mini AC unit. Thus, make sure the calculation is completed appropriately.
What is the best method for sizing a circuit breaker?
In truth, all three methods are great for determining the right switch size for your mini AC split unit. But you have to be a little careful when doing the calculation part. One wrong step can lead to disaster. This may burn the AC unit circuit. Or an electrical fire could start.
And if you can use at least two methods for the same device, it will be safer. Also, if you feel uncomfortable performing such tasks, be sure to seek help from a qualified professional.
