Why does my compressor pressure relief valve open?

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by chris daniel
(mooresville, nc)

I do not know how to adjust the pressure release settings so the safety valve does not blow for a Speedaire 5Z185A.


Speedaire 5Z185A   pump

Chris daniel

Hey Chris, nice to hear from you.

Listen, if your PRV is going off and the pressure in the tank is higher than the normal cut off pressure for that compressor, that means that the pressure in your tank is above the safety release pressure of your compressor system.

If the PRV is cracking open at a pressure below the normal compressor cut out pressure then it may be that the PRV is fouled.

Stop using the compressor. Unplug it and drain the air.

That your pressure continues to rise after your compressor has achieved high pressure cut-out in the tank, and the compressor continues to compress air without shutting off, you’ve got a pressure switch problem.

Install a new one. Check out the Speedaire page on this site for help in getting parts for your Speedaire.

My ebook, The Home Compressor, covers many aspects of troubleshooting the home compressor, including changing out the pressure switch. Check it out on this site soon if you get the chance.

Replace PRV

by Sheldon
(Apex, NC)

I am glad this site is here!

I recently “horse traded” for an older 20 gallon Speedaire compressor.

Somewhere along the way somebody swapped the original 2hp electric motor for a 5hp Gas Clinton.

I have the Clinton starting on the first pull now and need to replace the PRV.

The previous owner hastily replaced it and it “pops” at 130 and does not reset until 50. I would like one that resets back at 90 or so. What are my options?



That your PRV is “popping” at all tells me that your compressor pressure switch cut out pressure level is too high for, or your PRV isn’t suited to, the compressor.

That you have one that resets is good, most of them on smaller DIY type air compressors simply need to be pushed back to reset them.

I can’t tell you if the 130 PSI “pop off” is right for your compressor, though that cracking pressure sure seems a bit low, since PRV’s are a safety device and are the last line of defense if the pressure switch fails and prevents a tank over pressure.

If it were me, I’d take the PRV out of the line, and run the compressor, keeping a careful watch on the tank pressure level. Be ready to turn the motor off. Watch the pressure. Maybe the pressure switch is set to shut off at, say, 150 PSI (which is not a too high range normally) and the compressor will shut off then.

That being the case, visit your local compressor repair shop and ask to buy a PRV that opens at about 10 PSI higher than the cut off, and one that needs a manual reset.

And… PRV valve pulsing

The aftercooler prv valve pulses air out while running. I think it may be a stuck valve.

Howdy, and thanks for writing in.

If the PRV valve is pulsing, it’s because it’s venting pressure from your system. That is it’s job.

What is the pressure in your system when the PRV pulses? I’m going to guess that it’s above the normal cut out pressure, and that you may have a pressure switch malfunction.

Pull the ring on the PRV and open it manually, and then shut it again by pushing in. If it’s pulsing still, then I think it’s working fine, and you have a problem elsewhere.

Is the aftercooler between cylinders? If so, that would suggest a failing intake valve in the second cylinder. If the aftercooler is between the cylinder and the tank, that may mean a stuck or slow tank check valve.

More details, please.


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