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compressor unloader

by Jeff S
(Illinois)

I have a homemade unit that won't allow the motor(3/4h.p.) to turn over the compressor when the receiver is pressurized which obviously blows fuses in my garage if I leave it energized over a few seconds. I have a 1/4 in. copper line piped from compressor head directly to the check valve, which by the way is working properly. Will a bigger motor solve my problem or do I need an unloading valve between compressor and check? I don't have a pressure switch on this unit to automate it somewhat, but I can't until this first problem is remedied. Any info you can give would be great!






Bill answers...

Hey Jeff:

It's the absence of the unloader valve that's an integral part of a standard pressure switch that's likely your problem.

Electric motors draw higher amperage when they start. An electric motor that's trying to start against a higher load (eg: moving a cylinder piston against a charge of compressed air)will draw more amperage than normal, and this higher draw is likely what's blowing your fuses.

If you've got the amperage in your lines to feed a higher HP motor, sure, that would help.

Be easier to integrate a pressure switch though.

Not having a pressure switch seems a bit puzzling to me. What turns your compressor off when it reaches your high pressure set point?

Cheers,

Bill

Comments for
compressor unloader

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Oct 21, 2008
absent pressure switch
by: Jeff S

Thanks Bill,
After posting my question, I searched the internet for pressure switches and discovered that the unloader valve was part of it. This homemade unit was left in the garage from the previous owner and it has a light switch on a nearby wall to turn off and on manually. Go figure! I have another question though. The 1/4 in. I.D. copper line supplying the receiver gets super hot. Should I be using a larger diam line to reduce the restriction on flow, thus reducing the heat produced?

Thanks , Jeff S.






Hi again, Jeff.

The processing of compressing air generates heat...and lots of it. That's why modern DIY home compressors have heat shields over the compressor pump. The head gets hot enough to burn.

The line leading into your tank is copper because the compressor head gets very hot. I don't think that enlarging the line will make any difference, as it's the heat being transmitted from the compressor head that heats it up.

If you are adventurous...go ahead and try it. I just don't think it will make any difference to the temperature of the line.

Cheers,

Bill

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