That your air compressor trips the breaker when the pressure drops can be caused by a host of air compressor issues.
Let’s look at what is happening in sequence, to see if this helps you determine why your compressor trips the breaker when the pressure drops in the tank, and the normal result is that the air compressor starts.
- The compressor tank is full of air and the compressor has stopped running
- You start to use air from the compressor tank however that occurs, blow gun, tire chuck, air drill, air sander and so on.
- The tank pressure continues to drop until that pressure level reaches the cut in pressure of your air compressor
- The compressor tries to start and instead of the compressor motor starting and filling the compressor tank again, maybe the lights dim for a second or two, and bam, the breaker lets go or the fuse blows
What happens when the tank pressure reaches the cut in setting?
When the tank pressure reaches a certain pressure level, the compressor should start.
What is happening at that point is the air pressure in the tank can no longer overcome the spring force inside the pressure switch, one of which is shown below, and when that happens the pressure switch flips to on, it allows power across the now-closed points, electricity flows to the motor circuit, and the motor starts.
At least that’s what is supposed to happen.
Compressor pump stays pressurized
When the air compressor reaches the cut out pressure setting, the pressure switch trips to off, and power stops flowing to the motor.
There is commonly air trapped over the piston, or compressor pistons, when this happens.
Since the typical compressor motor is barely able to start a compressor pump when there is no air trapped over the piston, if there is air there, the motor normally cannot overcome that additional load, it attempts to start, pulls too much current in trying to do so against the force of the trapped air, and the breaker or fuse lets go.
The first thing to check if the compressor trips the breaker when the pressure drops
The first thing to check then, when your air compressor trips the breaker when the pressure drops, is if there is air trapped over the pistons. How do you do that?
To test to see if this may be what’s happening, turn off the compressor or pull the plug, and drain the tank fully. Close the tank drain and start the compressor. Did it start OK?
You see, by draining the tank what you have done is drain any air pressure over the piston too, and by removing that additional load you have made it easier for the motor to start.
Air over the piston should evacuate automatically
When the compressor is operating normally and the tank pressure reaches the cut out pressure setting, the pressure switch trips to off, the motor stops… and then, the Unloader Valve is supposed to open to allow air over the pistons to evacuate.
In the scenario shown above, what the problem is most likely to be, is that the Unloader Valve is not operating as it should.
Could there be other issues causing the compressor to trip the breaker when the compressor starts? Yes, and all will be addressed on the pages of this site. A malfunctioning unloader valve is typically the foremost reason why this air compressor problem occurs, though.