Air compressor cannot restart when reaching low pressure setpoint

by Jacques Pagé
(Montreal QC Canada)

My Compressor (belt driven iron pump) starts OK when empty and runs until it reaches the set PSI value.

When I use the air and the pressure reaches the low point, it refuses to start again, tripping the breaker.

I thought it was the motor so I went to a shop to have it checked and they told me it was OK. Then I went to another place and they told me the pump is fine...What would be the problem?

Could it be some kind of back pressure in the pump, rendering the restart so hard as to overcome the motor's capacity on start up? If so, what causes it?

Thanks

__________________
Bill says...

Bonjour, Jacques!

Drain the tank, start the compressor, and monitor the unloader valve as the compressor tank pressure reaches the cut out level.

Make sure the unloader valve works. See the Unloader Valve page if you are not sure what that is.

If the unloader valve does not work, that is your problem. If it does, and does so two or three times, then post a comment here to let me know, and we will delve deeper.

Salut,

Bill




Comments for
Air compressor cannot restart when reaching low pressure setpoint

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Jan 19, 2008
 More on Compressor Restart
by: JimG

Jacques:

Thats it.

Your start switch is not venting properly.

If the pump piston on start up has full pressure on it, it can not turn over against the pressure.

Your pumps piston needs NO pressure to turn over and your pressure switch does this.

Sometimes you can hear a blast of air from a compressor when it shuts off and vents this air for the next start.
Dec 12, 2007
 Compressor Restart
by: Bill - Publisher

Jacques...nice hearing from you.

Though I am not a compressor mechanic, it seems to me that your problem is your pressure switch.

The pressure switch should have an unloader valve built in, that, when the pressure in the tank reaches high set point and the compressor stops, it unloads the air over the piston, allowing for easier restart.

Usually you can hear when the unloader valve dumps the air.

So, my thoughts are that either the unloader valve isn't working and the electric motor hasn't enough power to over come the load on start up, the motor stalls, and the breaker pops, or the pressure switch itself is defective. Either way you'll need a new switch.

I can't think of anything else...but again, I'm not a mechanic.

You can pick up a pressure switch by clicking here.

Anyone else have any thoughts on Jacque's problem?

Bill

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