Having the proper breaker size for your air compressor is vital for many reasons. First and foremost, it’s going to save you time and energy. Second, it will stop your compressor from overheating and/or tripping your breakers.

So what size breaker do you need for your air compressor?

Most standard air compressors only require a 15 amp breaker to operate. However, In order to properly determine what size breaker you require for your air compressor, you need to look at the tag on the motor to locate the voltage requirements.

The guide that we have created will help you determine the size of the breaker your air compressor requires. Even though many select compressors only require 15 amps, other compressors may require more. We will help you figure out how much more.

Properly Sizing A Circuit Breaker

Do you find that your air compressor is constantly overheating or tripping the breaker? This is because your compressor isn’t fitted with the correct breaker. The size of the circuit breaker is determined based on their amperage ratings.

There are certain steps you can follow to determine the breaker you need by following a series of electricity formulas based on the horsepower rating of your air compressor’s engine.

These steps will help you make your calculation: 

  • Convert horsepower to watts. 1 HP equals 745.7 watts
  • Multiply the HP rating of your air compressor by 745.7 and you will get the power wattage
  • Since breakers are sized by amperage, multiplying the voltage and amperage will give you wattage
  • Look at the tag on your compressor’s motor for the voltage requirements
  • Divide the wattage you calculated earlier by the voltage requirements of your air compressor and this will give you amperage

Keep in mind that you can’t size your circuit breaker to the amperage you just calculated since the motor will draw more power at start-up than while running.

Unless you are knowledgeable with electricity, it’s best to consult with a certified electrician if you have to make changes to your circuit breaker system in your compressor. You can also refer to this guide to help you.

Check out this chart as well for some common amperage and wiring sizes:

Wiring Sizes

The electrical wiring that goes from the power supply to the electric motor will vary according to the horsepower of the motor and a few other factors. Installing the proper sized power leads can protect against a drop in voltage during start-up.

If you are connecting additional equipment to the same circuit, you will need to take the total load into consideration. Do not undersize the wire. 

The wire sizes below can be used as a safe guide if the distance doesn’t exceed 50 feet. If it exceeds 50 feet, you will need to consult with an electrician for recommendations.

Additionally, you will need to install the correct sized circuit protection. It’s important to keep in mind that when the compressor starts, the current will be greater than when running the full load current. A slow blow fuse is recommended.

Single Phase

Motor HP230V
310
58
7.55
104

Three Phase

Motor HP200V230V460V575V
310121414
58101414
7.5881214
10461010

Amperage Chart

Single Phase

Motor HP230V
330 Amp
540 Amp
7.540 Amp
10n/a

Three Phase

Motor HP200V230V460V575V
3n/an/an/an/a
530 Amp30 Amp20 Amp20 Amp
7.530 Amp30 Amp20 Amp20 Amp
1060 Amp50 Amp30 Amp30 Amp

Slow Blow Fuse

We briefly mentioned a slow blow fuse earlier in the guide. The slow blow fuse is a type of fuse that can take on a temporary surge current that exceeds the current rating of the fuse. It doesn’t blow when a temporary surge happens.

Rather, it receives a sustained elevated current above the current rating for a short period of time before it blows. This is where the term “slow blow” comes from.

Generally, a fuse will blow immediately once it receives a current above what it’s rated for. When this happens, the fuse is no longer viable. A slow blow fuse, on the other hand, is constructed differently.

It contains a coiled construction and is designed to open only on a continued overload like a short circuit.

Slow blow fuses will only blow when it detects an elevated sustained current spike over a period of time. They are designed to work even if the equipment is struck by lightning. These do not react to momentary spikes, just continued overloads.

Voltage & Circuit Protection

Due to a lack of voltage and circuit protection, your air compressor can overhear. As long as certain safeguards are put into place, a 15-amp circuit can be used to operate select air compressors.

To determine whether or not your compressor can run on 15-amps, here are the following safeguards:

  • The voltage supply to the circuit must follow the standards of the National Electrical Code
  • The circuit can’t be used to supply power to any other item
  • Extension cords being used have to meet specifications listed in the manual for the air compressor
  • The circuit must be equipped with a 15-amp circuit breaker or 15-amp time-delay fuse

An improperly sized circuit breaker or time-delay fuse can cause overheating. If your compressor is connected to a circuit protected by fuses, you should only be using time-delay fuses. These fuses are denoted by a “T” symbol.

Improper Extension Cords

If you have your compressor plugged into an extension cord and there’s a lot of heat coming from the machine, it’s very likely that that extension cord is the problem.

If your extension cord is sharing an outlet with other machines that have high amperage or the cord is not powerful enough to ground the machine, then the compressor won’t run the way it should. Your machine will still operate, but it won’t have enough power to run it as efficiently. You will find that more heat is being generated due to being overworked.

Additionally, if your extension cord is too long, it won’t supply the compressor with enough power. You will need a shorter, more powerful cord or you can move the cord and machine to a socket that’s closer to the panel box.

Overheating Protection

If your circuits are correct but you still find your air compressor overheating constantly, there could be other issues at hand. One of the biggest issues air compressors have is that they get too hot.

They are constantly suffering from fluctuations in temperature, which could be either overheating or freezing. Overheating can cause damage to the compressor and shorten its lifespan.

Sizing branch circuit conductors
Photo from ecmweb.com

It’s completely normal for the compressor to be hot on the inside since the process of compressing air can generate a lot of heat. However, sometimes the compressor can overheat due to other factors.

Other Reasons Compressors Get Hot

Air Temperature & Humidity

The air that surrounds the air compressor can have an effect on the temperature inside of the system. The ambient air temperature range should be 50-85 degrees Fahrenheit for an air compressor.

Additionally, humidity can have an effect on how well your compressor performs. The compressor should be operated in dry or low humidity conditions. This is due to the fact that there will be less condensate inside your compressor. In short, there will be less moisture that needs to be removed from the compressor.

Poor Ventilation

Every air compressor contains openings for ventilation to help regulate its internal temperature. You should always ensure that the openings on your compressor are free of blockages.

It is recommended that you never place objects on or against your compressor, never operate the compressor in a confined space, and keep the air compressor at least 12-inches from walls or other items that will interfere with its ventilation.

If you have no choice but to operate your compressor in temperatures over 85 degrees, here are some recommendations:

  • Ensure there is a supply of fresh, cooler air in the area where the air compressor is being operated
  • Open a window or door to ensure fresh air is available

Other than the reasons specified above, there are other reasons why air compressors can get hot. One of the main reasons is that friction occurs when air molecules are squished together.

When this happens, it creates heat. The hot air will then move through the pump head within the compressor into a receiver. You can feel the heat at the copper line that connects those two parts together. Not only that but the heat can be felt in the motor and the compressor head.

It’s completely normal for compressor parts to get hot sometimes, especially if they’re being operated constantly or if it’s warm outside. Unfortunately, if your compressor feels hotter than it should, then it’s probably overheating.

Overuse

If your compressor doesn’t exceed the allotted duty cycle and the heat isn’t excessive, then your compressor isn’t overheating. However, if your compressor hasn’t reached the duty cycle and the compressor is hot, you’re most likely experiencing overheating.

It’s best that you stop the compressor every 10-15 minutes to give the motor a break.

The Takeaway

It may seem like an easy task if you’re experienced with electrical applications, but for others, it’s best that you consult with an electrician. The guide we have created should help you get started at least. There are numerous charts and recommendations on this website that can give you some more insight into wiring, circuits, and much more.