Compressor wont start unless tank is empty?

by Rodney
(Houston, Texas, USA)

I have a 80gal 220v Delta compressor and if there is any pressure in the tank it will try to start and struggle and then trip the breaker after about 6 seconds.

I replaced the pressure relief valve that unloads the pressure from the pump and I even put on a start capacitor and run capacitor (I hope I have all the terms right since it has been over a year since I did all this). The only way it will fill is if it is 10psi or less. Any pressure above 10psi and it will trip the breaker. I really need to get this working correctly since I now need to start using it more than I have been.

Any ideas with what could be the problem?

Much appreciated.

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Boy, I wish you had uploaded a photo of your Delta compressor. I was unable to find one to help me understand the issues.

However, one reason the compressor motor won’t start – and blows fuses or breakers – is because the motor draws too many amps on startup, exceeding the capacity of the circuit breaker, and it pops.

A common reason for excessive motor load on startup is that the compressor hasn’t unloaded properly when it reached cut out pressure and stopped.

To be sure that this isn’t your compressor problem, bleed the tank to zero pressure, start the compressor, and let it fill to cut out pressure.

Observe and listen near your unloader valve to be sure it activates when the compressor stops. If it doesn’t that’s your problem.

Since you appear to have corrected any potential problems with the motor, please also check and see what else is on the supply circuit to the compressor. If another device is starting or running and drawing power from the compressor circuit when the compressor tries to start, that too could be causing a problem.

Please comment on this thread to let me know if the unloader valve is not, for sure, the problem.

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