Help plumbing air compressor unloaders....

[jmilch]

Greetings guys, first post

Most of my internet related searches have brought me here, although I could not find an answer to one question...

I bought a new compressor pump, and it is a triple cylinder, single stage. As a added feature, it has individual head unloaders (on top of each head).

They are plumbed together, with the outlet being on the left hand cylinder head. Here is a picture (the copper lines between the heads are the connected to the unloaders):

The tank I am using was bought used, and had no pump or motor on it. Here is the pressure switch (came off a Quincy QE10)

And where it connects to the tank:

Can I plumb the head unloaders into the tee on my tank that runs to the unloader on the pressure switch?

Thanks for the help guys. I just have never used a compressor that had head unloaders.

 

[The Cobbler]

the unloader is on the pressure switch . looks to be a 3/8" copper line with compression nut at the switch

 

[G_P]

I think you can plumb your unloaders into that tee. When the pressure switch clicks off, it depresses that pin and vents the air out of the unloader line.

I would also replace that safety blowoff valve. Looks to be packed full of greasy crud. Not a part you want to fail when it is needed!

 

[jmilch]

Thanks guys. I removed the pressure switch and thoroughly cleaned it. I also removed the unloader line and cleaned it and the pin. I have a new blow off valve ordered. And I figured I could plumb the new unloaders into that "t". Thanks for the tips!

 

[safetyman665]

Not sure that I see it in any of your pictures, but you will also need a check valve to work with your unloader. The valve should be directional from the pump into the tank and the unloader should be piped in after the check valve to prevent the "unloaded" pressure from returning to the pump.

 

[EOC_Jason]

I would think / hope that main fitting on the tank is the check valve where the unloader line runs to.

 

[TapperMan]

I have a very similar pump, a Curtis ES-20, which has the same unloader design. I temporarily was running it with a gas engine, and used a pilot valve to send air to the unloaders (and a throttle control) when it reached max pressure. You could use a similar setup with an electric motor if you wished to use it in a continuous-run configuration.

The head unloaders aren't really needed if you have a pressure switch which unloads the discharge line, unless you want to avoid starting your electric motor too frequently.

Pilot valve:

Line to head unloaders:

 

[jmilch]

Not sure that I see it in any of your pictures, but you will also need a check valve to work with your unloader. The valve should be directional from the pump into the tank and the unloader should be piped in after the check valve to prevent the "unloaded" pressure from returning to the pump.

Yes it has one. The center stem of the tank (covered in tape) is a complete check valve assembly. The pump was damaged and removed, and the motor was removed and sold. But the tank, pressure switch, unloader line, fitting and check valve were left in place.

 

[jmilch]

I have a very similar pump, a Curtis ES-20, which has the same unloader design. I temporarily was running it with a gas engine, and used a pilot valve to send air to the unloaders (and a throttle control) when it reached max pressure. You could use a similar setup with an electric motor if you wished to use it in a continuous-run configuration.

The head unloaders aren't really needed if you have a pressure switch which unloads the discharge line, unless you want to avoid starting your electric motor too frequently.

Pilot valve:

Line to head unloaders:

Thanks for the pics. I was kind of thinking the same thing. I did not see the point on a non continuos running setup of having the top unloaders connected. It seems like the discharge line would already be discharged from the normal unloader setup.

Now the head currently has just bolts installed in the location of the top unloaders. The directions make no mention of not using the head unloaders. They also are not the best directions.

Would there be any harm in just not removing the bolts, and not installing the head unloaders and just using the standard discharge line unloaders?

The literature with the pump stated they could be used "continuous operation". I am guessing it is just a feature likely to be used with gas engines or other purposes where the compressor would be allowed to stay running after the fill pressure is reached.

 

[TapperMan]

Yes, you should leave the plugs in if you are using it with an electric motor and pressure switch.

If you want to see what's under those plugs, I made a thread about disassembling the valves when I was getting my used pump running... http://garagejournal.com/forum/showthread.php?t=207510.

 

[MacMcMacmac]

Those head unloaders are completely redundant in a start/stop application. To try to plumb them in in any manner in which they would be useful is a waste of time. You would need some way to send air to them at cut-out, then dump the air to them once the compressor was up and running. As this is a splash lube pump, you cannot use oil pressure to do this. You would need a separate air feed from the tank, hooked up to a solenoid valve which would open at cut out. Not impossible, and it would work well, but more elaborate than you need, and more stuff to go wrong. Without trying to sound like an ***, I'd say put the money into a new pressure switch. That one looks like it has had a lot of oil through it.