Compressor short cycles after the cut out pres. has been reached

by Robert V Chowuette
(plainville conn.)

this compressor is used on a dry sprinkler system,when turned on it reaches the proper cut out pres. approx 15 plus minutes later it short cycles for about 90 sec. and shuts off. no visible leak is noticed in the surrounding piping, and no visible drop in pressure on the gauge, this is somewhat annoying to the customer and puzzling to me.





Bill says...

Hi Robert:

When you say it short cycles, you mean that the compressor turns on, runs for 90 seconds and then shuts off again?

During that 90 second run, are you seeing and pressure increase on the tank gauge?

When it short cycles, does it wait 15 minutes or so then short cycle again, or does it now stay off until the cut in pressure is reached?

I'm wondering two things. One, that you have a bit of a leak from the check valve going into the tank, and that air is bleeding our your unloader valve, though if that were the case in any volume, you should be able to hear it.

Two, the only thing that can turn your air compressor on is the pressure switch. If it's turning on the electric motor to begin compressing air, and the air pressure in the tank hasn't reached the cut in pressure, then it's got to be a pressure switch problem.

That, or the tank pressure is dropping to cut in pressure, and your tank gauge is frozen, showing a reading that isn't actual.

Good luck with this. Why not give us an update?

Thanks for writing in.

Bill




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Compressor short cycles after the cut out pres. has been reached

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Nov 17, 2009
 Air compressor short cycling.
by: robert v. choquette

bill,thanks for the reply and here is some clarification:

compressor runs from cut in to cut out pres, stops
approx. 15 min. later it turns on again for about 90 sec.

during this 90 sec. i find no increase in the system pressure and have never checked the tank gauge, good point.

the short cycling only occurs when it has reached the cut out pres.

since this is a customer we have recently acquired,no manual exists, where can i get such a manual?

very difficult to find model # of unit. it has the following.1.0h.p. motor 1725rpm,tank is approx 36" long, and 8:dia. floor mounted unit.
_________________
Robert:

I think it has to be something to do with the pressure switch / unloader valve combination.

You see, if the pressure in the system doesn't drop to the normal cut in pressure level, why would the compressor start before the pressure level drops to that setting? Since it's the pressure switch that turns the compressor on and off, and it's turning the compressor on at the wrong pressure level, then - by default - something is awry with your pressure switch.

As to a manual, without a brand name (and often even if you have a brand name) compressor manuals are few and far between. If you can identify your compressor, send in another ASK question about finding a manual for that brand, and I'll move it to the appropriate trouble shooting page that asks for help in finding compressor manuals.

Also, I'm curious as to whether it short cycles again after the first 90 seconds run? Or does it do it just once?

B.

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