Need help with air compressor pressure control...

[rodder98]

I have a 5 hp unit that had a Furnas air compressor pressure switch installed on it. It shut the compressor off as designed, but then the pressure switch would leak air pressure down, from near where the 1/4" copper tubing attaches to the pressure control switch. The tank loses the pressure down to zero instead of holding pressure.
I thought the Furnas air compressor pressure switch was defective and replaced it with a Square D FHG12J52XCP pressure switch that is very similar. But, the new one also leaks the air down also when it shuts off.
Obviously, I am not understanding something, but I sure could use help knowing what causes the pressure switch to leak air down. What am I missing?

 

[metal4130]

I would need to see a picture to see how your compressor unloads but from what you say it is not your pressure switch at all. Your real problem is the check valve on the tank.

There should be a little a line that goes from the tank (check valve actually) to the pressure switch. When your compressor shuts off the pressure switch does its job and "unloads" all of the high pressure air that is left in the line. This makes it easier for the motor to start the next time because it doesn't have to fight the high pressure when it begins.

Problem is your check valve is leaky which allows air to escape the tank, travel through that small line and exit through the pressure switch unload outlet.

I say this is probably your problem because it depends on what kind of compressor you have. The higher end compressors unload through the compressor while others use the pressure switch to unload. I am betting you have the second option.

 

[jrsulo]

I second a bad check valve !!!!!!!

 

[rodder98]

The little 1/4" copper line going to the pressure control comes from the compressor itself, right next to the discharge line that goes to the tank. It is a Campbell-Hausfeld with a 60 gal. tank.
So, where might I find the check valve? You make perfect sense. I didn't know there was a check valve.

 

[jrsulo]

Its right there where the line goes in.....its screwed into the tank.

 

[rodder98]

I can feel the air leaking where the copper line attaches to the control. (Not at something screwed into the tank.) Could there be a check valve screwed into the compressor where the 1/4" tubing connects to it, and then the tubing attaches to the check valve? I am a few miles away from my garage at this time, but i will look tomorrow.

 

[jrsulo]

Ihe air is just leaking at the easiest way out......and yes......the 1/4 line screws into the check valve.

 

[jrsulo]

Dont know what size your comp takes but it should look like this ......http://www.northerntool.com/shop/to...i_sku=407103&gclid=CLq29of70rYCFYtT4Aod5DcAvg

 

[rodder98]

Thank you for your help. I understand now, and I will check it out and replace the check valve. You are terrific.
I have a pretty good electrical and mechanical background, but this is the first time I have ever had an issue with a compressor, so I learned something new.

 

[metal4130]

Check valve for sure. Good news is they are not expensive. There are 2 main types of check valve, the in-line and the in-tank. What you have is the in-tank which is by far the most common. Much of the valve is hidden in the tank. That 1/4" copper line screws right into the check valve.

There are many mfgs. but here is one for example:

http://www.kingstonvalves.com/25/Products/19/2/parts_details.aspx

Measure what you have and search eBay for compressor check valve.

 

[Charles (in GA)]

http://www.surpluscenter.com/sort.asp?catname=air&keyword=AVC1

1/2 or 3/4 or 1" pipe thread in the tank, and 1/8" unloader port for the line to the pressure switch. Get the correct valve that has the correct threads all around, so you don't need adapters. Yes, the check valve is leaking the tank pressure back to the pump and the unloader line and valve are doing their job and dumping it.

Charles