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Why are solenoid valves directional?
- Thread starter Don B.
- Start date
MEP001
Well-known member
A solenoid is essentially a check valve with a coil that pulls the poppet open to let flow through the opposite way. When it's closed it uses the pressure behind the poppet to keep it closed. D/H systems used the solenoids in reverse so the cold water rinse can't back up through the solenoid and into the chemical tanks. In the case of soap and wax supplied to a pump, the spring pressure on the poppet is enough to keep the soap and wax from flowing when it's not called for. It only requires a few PSI for pressure to force the poppet open, so you can't run them in reverse to control pressure. There's D/H equipment out there over 50 years old with the solenoids plumbed in reverse, so I don't think it shortens their life. I started doing the same thing about 20 years ago when I was seeing a high failure rate of the low pressure check valves on the soap and wax lines. Free fix and removes something that could fail.
I see now. So you could really only run them in the reverse if there’s no pressure behind them, such as soap and wax. I could see where it would work good for soap and wax solenoids if it was gravity fed. Don’t think it would work on my pressurized soap and wax system. It would probably push the rest of them open.
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I must have missed that one on the test!
MEP001
Well-known member
It won't work with any pressure. It works well with gravity though. I've even tried starving the pump for water to see if the suction will pull pull the solenoid open, and it doesn't.
