strange pump issue

[mac]

I have a customer with a prep gun that is kept at 2000 psi. It has a non weep gun, so that when the trigger is released all flow to the gun stops, and the unloader sends the water back to a tank. It's been working fine up to now. Now for some reason when the trigger is pulled, the amperage on the motor goes up 10 amps and the overload trips. When the trigger is released the amperage goes back down 10 amps. Any thoughts?

 

[Randy]

The first thing I’d do is replace the Unloader.

 

[mac]

That's kind of what I was thinking, only it seems odd that it works when the trigger is not pulled.

 

[MEP001]

An unloader literally unloads the pressure from the pump. The hose still has pressure trapped in it, but the pump/motor is just running the water around at no pressure so it doesn't generate heat and uses less energy. If the unloader fails to work properly, the pressure in the pump increases about 50% when the trigger is released. Since the motor is running near its peak output under normal conditions, it trips the breaker.