How Solenoids work??

[Waxman]

My water supply that feeds my low pressure boost pump is backfeeding into my high pressure rinse tank, causing an overflow situation and wasting water.

I have isolated it to the high pressure wax injector and 2 solenoids on the manifold on my pump stand.

From the manifold side, there is 1 solenoid then the wax injector then the other solenoid then the feed line for wax to be delivered to the h.p. pump.

Maybe 1 solenoid is normally open and 1 is normally closed???

Any ideas?

Must be one of these solenoids. Just can't figure out why water would get by both solenoids unless it's like I thought and 1 is norm. open and the other norm. closed???

 

[MEP001]

Solenoids won't stop a flow in the reverse direction from their operating flow, it doesn't matter whether is't normally poen or normally closed.

 

[Waxman]

Well I first thought it may be a check valve, but I took all those apart and thought it was not a check valve.

Then I pulled the hp wax line off below these 2 solenoids and water poured out the bottom one until I shut off the low pressure pump feed lines then the water flow from below the wax 1 solenoid stopped.

 

[pitzerwm]

Solenoids plumbed backwards can work as a check valve, but not for much pressure.

 

[madscientist]

I'm not entirely sure I understand your setup, but can I assume that the solenoid which has the leak associated with it is feeding the HP Wax through the HP pump and the other solenoid is for a separate LP wax cycle?

If so, the following may be the explanation:

If that solenoid (normally closed) is not sealing, then it is allowing LP solution to flow backwards through it and into your tank, while the other solenoid on the same line is in use (normally closed, but open while in use). Your LP pump pressure is strong enough to force the backwards flow through your pump and into your tank.

If I'm wrong about your setup, just ignore this.

 

[Waxman]

The problem was crud in the top solenoid out of 2 on the hp wax injector.

It goes manifold, solenoid, injector for hp wax, solenoid then plastic line to hp pump.

The problem was solved when the top solenoid was cleaned and reassembled.

Thanks everyone.

 

[MEP001]

Solenoids plumbed backwards can work as a check valve, but not for much pressure.

Depending on how you look at it, a solenoid is just a check valve that is made to open to allow flow in a reverse direction. I did plumb the soap and wax solenoids for the self-serve backwards to eliminate a check valve, and the spring pressure is all that stops the flow. The city pressure on rinse is stopped from getting to the soap/wax tanks by the normal operation of the solenoid. I wasn't thinking one time when I used a jumper wire to turn on the rinse solenoid and pump and had the switch in the soap position - it caused a customer to get no soap.