Water Wizard Cat 3535 Pump/Unloader Issue

[toddmullens]

I have about 14 of these units in operation and I am having an issue from two or three of them. These units are holding pressure after the pump turns off, which is causing the pump to start under a load at times. I have installed an “off delay relay” on the top spray boom solenoid to keep that solenoid open for a couple seconds after the high pressure pump turns off and that seems to have fixed the issue for the most part. Now it only does it after the undercarriage turns off. What’s strange is that it doesn’t do it on the rocker panel function, only the undercarriage and regular hp rinse function. I know the rocker pane uses a bigger solenoid and undercarriage, side spray, and top boom spray all use the same type of dema solenoid. I have replaced all the high pressure solenoids and unloader (I made sure the check valve was removed from unloader) and still had the same problem which is why I installed the off delay relay on the top boom spray solenoid just to relieve the pressure aa much as possible. I can’t understand why some of these units do this and others don’t. They are all plumbed identically. I just wonder if there is an off delay programmed on the solenoids within the programming that isn’t working on some units...I am at a loss. Anyone else experience this?

 

[Greg Pack]

Well, I was going to tell you to remove the parts from the unloader but you've done that. So I got nothing, except maybe check your unloader plumbing back to the pump. Let us know what you figure out!

 

[toddmullens]

I have been battling this for awhile. I doubt I ever figure it out. It’s like either the pump runs a split second too long or the solenoids are closing a split second too fast. It’s frustrating and baffling! I wouldn’t be concerned about it but I think this is what is causing the valve springs to randomly break. I spoke to cat service and they said excessive turbulence or cavitation usually is the cause of busted springs and I have doubled checked every joint to ensure there is no cavitation. My guess is the slight dead heading of the pump when it shuts off is causing the turbulence to break the springs. I just don’t understand why it does not do it on the rocker panel function and only the rinse and undercarriage. It seems like they would program in an off delay on the solenoids or program the medium pressure solenoid to activate for a split second after the pump turns off as a safe guard to protect the pump.

 

[MEP001]

Can you tell if the pump is plumbed to reduce turbulence? On self-serve pumps I always plumb incoming water and return from regulator/unloader to the same port. Forcing the water to suddenly change directions with flow changes causes a brief cavitation.

Could you add a normally open solenoid that's powered off the pump motor to dump the pressure back to the tank, or does it use a VF drive?

 

[Greg Pack]

Does anyone at Coleman know?

What if you installed a normally open solenoid and wired in back in the motor starter circuit. Tee it back into the medium pressure line. Would that solve the issue?

ETA, I guess I should have read what MEP wrote

 

[toddmullens]

Good idea...I will try this.

 

[toddmullens]

Does anyone at Coleman know?

What if you installed a normally open solenoid and wired in back in the motor starter circuit. Tee it back into the medium pressure line. Would that solve the issue?

ETA, I guess I should have read what MEP wrote

I will have to inquire with Al and see if he has any ideas.