Hearing about the magnetic starter for air compressors can be overwhelming for individuals without any background in electric wiring. This becomes even more daunting when you realize that this component is indispensable for the safety of your motor.
Don’t worry, though. You are in the right place.
In this article, we will detail how to wire a magnetic starter air compressor and show you some practical examples.
What is a magnetic starter for an air compressor?
A magnetic starter (i.e., motor starter) is an essential component for air compressors that produce more than 5 horsepower (hp). The installation of the magnetic starter will add a layer of protection to your motor and pressure switch. It will also extend the lifespan of your compressor.
The chart below demonstrates the connections that a magnetic starter has with other components of the air compressor:
Why do you need a magnetic starter for an air compressor?
Here are some reasons why a magnetic starter is needed for an air compressor:
Protects the pressure switch and motor
A magnetic starter has integrated overload protection that prevents the motor from drawing excessive current. Without this protection, the motor can overheat.
Research shows that overload protection can actually extend the lifespan of the motor.
Manages the starting current
Electric motors use up to 6 times the current when starting. Over time, this can have a toll on your motor. Luckily, magnetic starters manage this high current thanks to contactors.
These contactors consist of:
- An electromagnetic coil
- Contacts
- Control circuit
You can think of contactors as a super relay that protects the circuit and manages the current that reaches your motor during compressor starting.
Controls the operation of the air compressor
Most modern magnetic starters for air compressors include an ON/OFF switch. This might not be a revolutionary feature, but it’s quite helpful.
You may also find an adjustable amperage overload, which you can set according to the amperage of your compressor (more on that later).
Finally, a few magnetic starters have control features, such as an emergency stop and a reset button.
Allows you to remotely control the air compressor
In industrial settings, magnetic starters for air compressors can be integrated with automation systems. This allows workers to remotely control the operation of the air compressor.
This feature is mostly useful when the compressors are set up in a hazardous area.
Reduced wear and tear
All the features listed above contribute to preventing wear and tear of the motor. Over the years, it will save you thousands of dollars on repairs. In some instances, you may even have to buy a new compressor motor.
The role of magnetic starters in protecting the pressure switch
In reality, many manufacturers choose not to include a magnetic starter in their air compressors even when the power is above 5 hp. The purpose of this step is to sell the compressors at a cheaper price point. Unfortunately, the consumer of this product will deal with recurrent burn-up of the pressure switch. This may occur every few months.
To save yourself from replacing the pressure switch and protect your motor, you need to install a magnetic starter.
Which starter is used in the compressor?
The best starter for an air compressor that exceeds 5 hp or draws more than 15 volts is a magnetic starter. This component protects the motor and pressure switch from current fluctuations and offers additional functions to the compressor.
Each magnetic starter will be compatible with the power and phase of the compressor. For instance, the magnetic starter for a 5 hp, single-phase compressor is different from that of a 10 hp, 3-phase compressor.
The table below displays magnetic starters for different types of air compressors:
| Horsepower (hp) | Phase | Magnetic starter |
| 5 hp | Single Phase | Link |
| 7.5 hp | Single Phase | Link |
| 10 hp | 3-Phase | Link |
| 15 hp | 3-Phase | Link |
| 30 hp | 3-Phase | Link |
How to wire a magnetic starter air compressor
Wiring a magnetic starter for an air compressor should be an easy task if you know what you’re doing.
Note: The following instructions are provided for educational purposes only. If you’re not experienced with electrical work, we recommend that you seek the assistance of a qualified electrician.
Before starting, you need to make sure that you are taking proper safety measures:
- Ensure that the power to the circuit is turned off.
- Follow all local electrical codes and regulations.
- Use appropriate personal protective equipment.
To facilitate wiring the magnetic starter air compressor, we will divide the process into 5 simple steps:
Breaker panel – magnetic starter
Take the two wires from your breaker panel and connect them to terminals 1L1 and 5L3. The magnetic starter should have two knockouts at the top that you can remove to set up the wires.
Note: This is a single-phase unit, so we do not use the central terminals. For three-phase compressors, you would need to use the central terminals.
The purpose of this step is to power up the magnetic starter, which will later serve as an ON/OFF regulator of the motor.
Magnetic starter – Motor
For this step, you need to take two wires from the 2T1 and 6T3 terminals and connect them to your motor.
These connections allow the magnetic starter to start the motor when the pressure switch detects a cut-on pressure level. Conversely, the magnetic starter will stop the motor when it receives a signal from the pressure switch.
Wiring the pressure switch
Connect two wires on one set of the pressure switch. Do NOT set up the wires on different sets of the switch. You can choose either set for this purpose.
The illustration above highlights what forms a single set in a pressure switch.
This step allows the pressure switch to start and stop the motor through the magnetic starter.
Pressure switch – Magnetic starter
Take two wires from the pressure switch and connect the first one to 1L1. This is the same terminal that connects to the breaker panel.
For the second wire, you can either connect it to A2, which is located below 1L1, or terminal 14. This is possible because terminals A2 and 14 are connected together with a wire (as demonstrated in the figure above).
Most magnetic starters contain overload protection that stops the motor when the electric current fluctuates.
Ground wires
Congratulations! You’ve made it to the last step.
All you need to do is connect ground wires to the ground screw. This step is important to protect the motor and other machines from short circuits.
Before restoring power, double-check that all the connections are in place. After that, you can turn on the power supply and test the compressor. The magnetic starter should engage.
What’s the alternative to a magnetic starter for an air compressor
If you don’t want to set up a magnetic starter for your air compressor, there are two alternatives to consider:
Heavy-duty pressure switches
Some pressure switch models can handle up to 25 amps without the need for a magnetic starter. However, these switches may not last forever, especially if your air compressor generates more than 5 hp.
Check out this pressure switch model by clicking here.
Variable Frequency Drive (VFD)
A VFD is another possible solution that controls the starting current but also allows for variable speeds of the motor. VFDs provide excellent control over the motor’s performance, including precise speed adjustment and soft starting.
Check out VFD by clicking here.
Takeaway message
Wiring a magnetic starter air compressor might seem daunting at first. However, once you understand the working principles of this product, it becomes a straightforward process.
We hope that this article managed to highlight how to wire a magnetic starter air compressor as well as the purpose of using this product.
If you found anything vague, please feel free to share your questions in the comment section below.
