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How to control a 24VAC valve from two signal sources, switching relay???

How to control a 24VAC valve from two signal sources, switching relay???

Old 02-26-17, 10:04 AM
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How to control a 24VAC valve from two signal sources, switching relay???

Hello All,

I have a 24vac solenoid valve that is used to fill a water holding tank, the valve is controlled by a float switch in the tank. I would like to add a water detector to the circuit that would keep the valve closed if it detected a over fill situation. I could install a second valve that the water detector would close but I was wondering if there was a relay that would allow the water detectors signal to over ride the "valve open signal" from the float switch. The entire circuit is 24VAC.

Old 02-26-17, 10:20 AM
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Welcome to the forums.

Why not just add a second float in series with the valve that opens
when it senses an overfill and closes the valve ?
Old 02-27-17, 06:02 AM
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Agree with PJmax’s solution. The failure mode being discussed is the float sensor does not remove power when the float reaches the full level . Adding the redundant float increases the probability of controlling the valve solenoid when the tank is full. However, if one sensor fails in the not full position, you are back to relying on one sensor to remove power to the valve solenoid when the float reaches the full level. You need to periodically test that both sensors are working properly to have the advantage of the redundancy.
Old 02-27-17, 10:43 AM
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Plus, you might consider a second solenoid valve. Plumbed in series with the first, and wired in parallel. Many dishwashers use this scheme to prevent indoor flooding.

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