Compressor Trips the Breaker When the Pressure Drops

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 trips the breaker when the pressure drops - Condor Pressure switch

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.

Here is complete information about the unloader valve to help you resolve this air compressor issue.

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.

 

Comments

  1. I have a 230v Iron Horse 16.5 cfm, with an Eagle motor. The motor starts fine, but throws the internal trip switch after only a minute or so of operation. The 35a fuse at my electric box never trips. After a couple minutes the trip switch can be pressed, but fails after another minute of operation. The unload valve is working appropriately, and I have replaced the run capacitor. What should I look to next?

    • If the power supply is clean, and your start capacitor has been checked, and you are certain there is no mechanical loading of the motor, then it’s pretty much got to be the motor. Check the run capacitor if it has one, and if that checks out, time to get the motor itself load tested.

  2. Rick Morgan says:

    My compressor will react the same as above when it reaches cutin pressure, depending on what tool is attached to it. Works perfectly when blowing up a tire or spray painting. When I attach a framing nailer, which requires more pressure to operate, the compressor will make a humming noise instead of cutting in and either trip the breaker or the reset button on the compressor. What would cause this?
    Rick

    • We have no idea why what air tool you have attached to the compressor would affect the cut in except that the larger the demand air tool the harder the compressor has to work, and that, along with a weak start capacitor and a hotter-running compressor motor, may have an affect. We would suggest you check the motor capacitors to see if one of them is weak or has failed.

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