Info about air compressor unloader valve

[jcarlosmor]

Hello to everybody in this forum.

This is my first post.

I would like to know if someone could provide some information about how to connect the pipe tubing to an unloader valve of an air compressor.

I bought an air compressor pressure switch like this:

http://www.amazon.com/dp/B00F3DFJ32/?tag=atomicindus08-20

As you can see there has four connections molded at the bottom (one at the bottom, and the remaining three at each side). I had used those four connections as following:

1) At bottom, to air compressed tank.
2) At right, to safety bleeding valve.
3) At center, to output for inflating, painting, etc.
4) At left, to manometer.

There is no problem with these four connections as they are pretty straighforward. The problem arises from the isolated bottom connection intended for the integrated unloader valve (near to the plastic gaskets for the electrical cabling in and out).

After attaching an 1/4 OD copper tube to this connection with their appropiate compression fitting (some kind of small copper ring), this valve is leaking air always. It is necessary an explanation about how I hook up the whole system:

My compressor ouput goes to a "T" shaped check valve. One end of this check valve insert itself into the tank. Since this check valve is a "T", the derivation goes to the unloader valve at the pressure switch. When the compressor starts running all the air leaks at the unloader valve in the pressure switch case.

And no, there is no problem with the check valve if you are thinking that maybe it could be a deffective check valve. I know that the check valve is ok after a simple test: If a seal the "T" derivation at the check valve, the compressor air goes directly to the tank filling it ok. I can stop the compressor and then unseal the "T" derivation": the air in the tank does not leak (or return) through this "T" derivation.

So the leaking is at the unloader valve into the pressure switch. How it is supposed that this unloader valve works? I can see a very small pivot that moves with the air, but there is no way of sealing it completely. I could imagine that maybe a small metal ball must be included (which my compressor switch did not include) that when the air is detected -that is, when the compressor is running- the metal ball floats and seal the unloader valve top. Am I right?

Thank you so much for your time and any help in advance.

Regards.

 

[CompressorPros.com]

The unloader on the pressure switch should actually be closed when the compressor is running. There is usually a small lever that lifts up and lets it seal off. When the compressor cuts off, the lever pushes a little pin down, opening the unloader. It is possible that the pin is bent, or the unloader is stuck open.

 

[jcarlosmor]

The unloader on the pressure switch should actually be closed when the compressor is running. There is usually a small lever that lifts up and lets it seal off. When the compressor cuts off, the lever pushes a little pin down, opening the unloader. It is possible that the pin is bent, or the unloader is stuck open.

Thank you for your reply. Exactly that was the function that I was expecting from the unloader valve. I can see a small pin (little "hat") protruding from the top of the unloader valve, but it seems that always leak air. Maybe is broken, since when I blow air with my mouth into the unloader valve, the air passes through to the top and leaks.

 

[Zeke]

That certainly is not a 'heavy duty' switch.

"This is a great switch for miniative (sic) air compressor It can help to save electric energy of the air compressor." — unknown Chinese author.

I'd send that one back before messing around with it. I suspect it will give you trouble on and on.

 

[edsauto]

If you feel like looking at it, take the brass part out of the bottom of the new switch. There should be a removable schraeder valve in the end, just like a cars valve stem.

You either have a bad schraeder valve or the brass part is in to deep on the cast section.If it is just a bad valve, unthread it and put a new one in. If the brass is to deep, try and shim it out with a few washers.

Dan.....

 

[jcarlosmor]

Thank you all of you for your advices.

I send the complete pressure switch unit for replacement and I got a new one. For this brand new one pressure switch, I blow hard with my mouth through the unloader valve and after a second or so I can feel the valve closed as expected, not letting me to blow more air through it, so this unloader valve is ok.

However, another issue arise trouble to me. This new unloader valve has inside a copper compression ring or fitting (cup or conical shape) with an inner diameter of only 6 mm! If I try to insert a common 1/4" copper pipe tubing (which is the size that goes to the check valve derivation), obviously it does not pass through this compression fitting.

Is 6 mm a common size for the unloader valve tubing (from check valve to unloader valve) ?

If I can't get 6mm copper pipe, could I use normal plastic hose tubing 6 mm OD (not pressurized) for this purpose of connect from the check valve to the unloader valve? I could figure that this connection does not imposes too much pressure since the pressurized air is way beyond after the check valve into the tank. However, I know of pump stalling from pressure issued in this connection also.

Could anyone share what is the diameter/material of their tubing from check valve to unloader valve?

Thank you very much for any help in advance.

Regards.

 

[GeneralDisorder]

I would go get some real hardware. That cheap form-x pressure switch sounds like trouble. First one leaks and second one will not accept 1/4" tubing. It is not uncommon to see metric tubing on cheap Chinese compressors. They usually use plastic tubing for the form-x which you can probably find in 6mm....

All that line does is relieve pressure between the tank check valve and the compressor so the pump can turn over without pressure from the tank working against it.

GD