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PostPosted: Sat Oct 11, 2014 8:02 am
I recently replaced my compressor pump. But I noticed that the new pump doesn't have compression release valve during motor startup. So the motor hast to overcome the full pressure of the tank to start up.

My upright (and the previous pump) has a valve that opens while the motor gets up to speed before it starts compressing.

I looked around on other replacement pumps, and I don't see this feature on them either.

It seems like there is too much resistance on the motor during startup. When the tank is empty, there's no problem starting up.

Just wondering if there's a way to add this feature.

-vetsen
Last edited by Vetsen on Sun Oct 12, 2014 10:14 am, edited 1 time in total.



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PostPosted: Sat Oct 11, 2014 10:18 am
Without knowing the pressure switch type and plumbing between the pump and tank,
It's difficult to troubleshoot your problem. You may try http://fix-my-compressor.com
and checkout the information on unloaders and check valves, and determine which components are either missing or not working with your pump configuration.
Sounds like your old pump had a centrifugal unloader, and the new pump does not.
Just a thought.



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PostPosted: Sat Oct 11, 2014 10:48 am
Higher end pumps have unloaders on the pump itself that unload once the cycle ends. The lower end or "weaker" pumps have built in unloaders that empty through the pump outlet and once the switch kicks off it empties the head through the check valve port to the pressure switch.

I think all pumps have unloaders some you can see on the outside and vent to the atmosphere, others are in the head and empty through the pump outlet.

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PostPosted: Sat Oct 11, 2014 3:39 pm
Also, did you go to a higher CFM pump and if you did are you sure the motor has enough power to drive it?



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PostPosted: Sun Oct 12, 2014 9:13 am
My compressor pump is
Image
from http://m.harborfreight.com/145-psi-3-hp-twin-cylinder-air-compressor-pump-67697.html. It's a bit low on the CFMl so I bought two. I was planning on having two motors, two pumps and one tank.

I have an old upright compressor that works good but does leak oil into my air supply, and has less CFM than one of these new pumps.


I checked out that fix my compressor site and found some good info. It looks like I need a tank check valve.
-Vetsen

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PostPosted: Fri Oct 31, 2014 7:29 am
That's the exact same compressor and motor I have. Mine has a Square D pressure switch which has an integral unloader valve. The unloader valve should be hooked up to the side port of your in-tank check valve.

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