The general recommendation is a 20A circuit breaker and 12 AWG (or larger wiring). The exact size may vary, though, depending on the size of the air conditioner. For instance, a 60,000 BTU mini-split may benefit from a bigger circuit breaker.
Remember that going with the wrong size can cause plenty of trouble in the future. For example, a circuit breaker too large can allow excess power to pass through the air conditioner, potentially damaging it. On the flip side, a breaker too small for the application may trip too often and unnecessarily, causing unnecessary alarms and necessitating costly replacements.
The rest of this guide should help you better understand air conditioner circuit breakers and how to pick the right one.
NB: We don’t advocate for DIY mini split AC installation unless you have some basic skills. Otherwise, you risk damaging the unit. It takes just one over-tight screw to damage some AC components. A DIY also exposes you to several risks. For example, interacting with refrigerant can cause severe respiratory issues, and electrical wiring can result in electrocution.
Factors that Affect Circuit Breaker Size
Before we get to the process of determining the correct circuit breaker for your air conditioner, it’s important to understand factors that typically affect circuit breaker choices. For heating and air conditioning appliances, the best circuit breaker choice depends on the following;
- MCA Amps: Minimum circuit amperes is a calculated value that specifies the minimum main power wire size. It refers to the highest steady-state electrical current that the HVAC unit should see when operating correctly.
- MOP Amps: MOPS refers to Maximum Overcurrent Protection. It tells you the largest size of your overcurrent protection device – a fancy way to say fuse or breaker. You can calculate the MOPS value on your own. However, it’s a complex process. At this stage, all you need to know is that the MOP value is the most relevant when determining the appropriate breaker size.
- Fan Amps: Heaters and air conditioners typically have fans to help with the distribution of conditioned air. However, these fans also run on electric current and must be protected from power surges. A standard mini-split fan draws about 0.25 amps, though a few may have bigger or smaller units, depending on the size of the air conditioner.
- Compressor Amps: The compressor uses electricity to ensure the smooth flow of refrigerant around the air conditioner. It also needs electricity to keep refrigerant at a good pressure. So, you can expect a much higher amperage value. A standard-size air conditioner draws about 17.3 amperes. But, again, the figure can be lower or higher depending on the size of the AC.
- Heating and cooling amps: Although mini-splits primarily depend on heat transfer to heat or cool the home, the process is facilitated by electricity. A standard mini split draws about 17.55 amps for heating or cooling. Smaller and larger systems may draw less or more current, respectively.
- Wiring: Finally, the choice of a circuit breaker is also dependent on the type of wire you’re using. Typically, you need a 20-amp breaker for 12 AWG (American Wire Gauge) or higher.
Focus On MCA and MOP
For mini-split air conditioner specifically, you want to focus on the MCA and MOP values. Fortunately, manufactures are required by law to provide a label with all the electrical information.
Minimum Circuit Ampacity (MCA)
The MCA value tells us how big the wire needs to be. Generally, if the minimum circuit amperes is 14.9 amps, then you need a 14-gauge wire. If the electrical label says it’s a 15.1 MCA mini-split, you need a 12-gauge wire and if it’s a 34-amp MCA mini-split requires an 8-gauge wire.
We must also mention that you don’t always need to match the circuit breaker size to the wire size for air conditioners. While it’s okay to do so, air conditioner compressors contain thermal cutouts designed to prevent damage to the units. The cutouts automatically open when there’s a power surge to prevent damage to the wires.
In addition to giving us a clue about the wire size, the minimum circuit amperes value also tells us the minimum size of the circuit breaker. So, the first step to choosing the right breaker size is to make sure that it’s not lower than the MCA value.
Maximum Overcurrent Protection (MOP)
The MOP value tells you the maximum circuit breaker size for that particular appliance. You must never exceed this value. Otherwise, there’s a risk of appliance damage during power surges.
How manufacturers arrive at the MOP value is a tad complex. However, the MOP trip value is often primarily dependent on the ampacity of the conductors used in the appliance’s circuits. The short circuit rating and interrupting rating are also considered based on the available short-circuit current in the circuit.
Typically, branch circuit overcurrent protection requirements are no less than 125% of the continuous load and 100% non-continuous load. The National Electrical Code (NEC) defines continuous load as load where the maximum current is expected to continue for at least three hours.
Beware that residual current circuit breakers, better known as Ground Fault Circuit Interrupters (GFCI), may have a small impact on circuit breaker sizing.
GFCI circuits increase the level of safety when it comes to running your mini-split. They’re particularly common in bathroom and kitchen applications, where contact with water is common. GFCI circuit breakers immediately break the circuit when electrical circuit leakage is detected, thus reducing the risk of shock and electrocution.
Unfortunately, most inverter types don’t match well with GFCI type circuit breakers. The reason is that GFCI isn’t rated for high harmonics. Harmonics refers to the voltage at the electrical frequency that an electrical appliance operates. GFCI easily trip in high harmonics.
Thus, these breakers are likely to trip easily due to the way inverter air conditioners operate. As such, most people end up oversizing the breaker to prevent frequent tripping.
Since it’s never a good idea to oversize a breaker, it’s best to forego GFCI breakers for standard AC applications. Instead, stick to regular circuit breakers with AC disconnect boxes.
If the Breaker Keeps Tripping
If you believe you’ve picked the correct size breaker for your air conditioner, but find that the unit keeps tripping, then it could be one of the following issues;
- A power surge: Power surges are the most common cause of breaker trips. Unfortunately, power surges are a complex issue that can only be diagnosed by a professional.
- Loose wires, short, or electrical component failure: For example, a failed capacitor may cause a short that trips the circuit breaker.
- Fan motor malfunction: If a clogged fan causes the motor to draw too much power, then the circuit breaker may trip.
- Frozen evaporator coil: A frozen evaporator coil tends to draw too much current. This can potentially trip the circuit breaker.
Other issues that may cause a rightly sized air conditioner breaker to trip include dirty condenser coils, refrigerant leaks, and compressor failure.
Most air conditioners will run effectively and efficiently on a 20-amp circuit breaker. But times come when you want a more accurate breaker size to match your AC. In that case, make sure the breaker is larger than the Minimum Circuit Ampacity (MCA) value and lower than the Maximum Overcurrent Protection (MOP) value.