Air Compressor questions

[oldn_rusty]

I'm fairly new to GJ, but lots to learn here.

I have a second hand compressor. It appears to be a fine machine, but I'm having a problem. When I first installed it, the piece that controls pressure and bleeds off excess, didn't work. The pressure side works and operates properly, but as soon as it shuts the power off, it triggers the air bleed piece.

I went to a local hardware store for a replacement, has all the same capabilities, and installed it. It does the same thing. I took it back to exchange it, and the replacement does the same thing. The two replacements are square D brand. That is not back equipment, there is something going on that I'm not seeing.

Why would 3 controllers trip the pressure relief valve, intentionally, in 3 separate controllers? Or is there a different question? What am I missing?

I appreciate all observations.

 

[md21722]

When the compressor shuts off it is supposed to bleed off a small amount of air. This is a feature called unloading so when the compressor starts up again, it is not loaded on the discharge/pressure side. If it continues to bleed down and drain the tank, then you need to clean or replace the check valve in the tank that the unloader line connects to.

 

[oldn_rusty]

Thanks. Who knew! I'll Check it out tomorrow. Had no idea there was a check valve in the mix. Assumed it had to do with the pressure relief process. Thanks alot.

I'm moving into my new shop, never had a compressor before so not familiar with them at all.

Rusty

 

[redmondjp]

Yes, that fitting that is right at the tank where the large compressor discharge line connects, and also the smaller 1/4" line that goes to the pressure controller (the unloader line), has a check valve in it which is supposed to keep the pressure in the tank from leaking back.

The pressure switch dumps the 1/4" line to atmosphere when the compressor reaches its shutoff pressure, thus depressurizing the larger line from the pump to the tank (thereby "unloading" the compressor). It sounds like your check valve is leaking or stuck open.

 

[The Cobbler]

yeah , well explained already . if it keeps bleeding air the check valve is bad, non existent or something. a few pics of the plumbing & model number would help. too

 

[oldn_rusty]

I learned a lot about my compressor and really appreciate the help with this issue. pulled the check valve and ordered a new one, last weekend. As you can imagine, all went well when the parts work, so I now have an air compressor, my first.

I'm putting the finishing touches on my new shop, moving equipment and tools in, rearranging to make the best use of all the new space.

Thanks for all the help.

Rusty