Aprilaire 550 humidifier problem


Old 12-07-04, 12:42 PM
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Aprilaire 550 humidifier problem

My humidifier runs when the fan is on. This is good. But it still runs regardless of where the hhumidstat is set at. The humidistat , wall mounted, is working ok. I checked it with an ohmmeter. But when I check for power at the solinoid valve and the fan is on the valve is always open regardless of the stat setting.

Have 24vac at the stat which feeds the water valve via a 5 wire cable of which only 2 are used.

Last edited by sumnerm; 12-08-04 at 03:06 AM. Reason: additional info
Old 12-07-04, 07:26 PM
Jay11J's Avatar
Join Date: Sep 2001
Location: Rochester, Minnesota
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When you said you checked it with a meter, so it open when you turn it down, and closes when you turn it up?

You are getting 24v at the valve all times, no matter what the stat is set at?

Check to see if the wire some where is crossed or shorted out.

How is your set up done? (transformer, feeds stat, the goes to the valve, the back to the transformer?)
Old 12-08-04, 06:10 PM
Ed Imeduc's Avatar
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Location: Mountain Williams Missouri
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If you take a wire off the humidistat does the valve close??
Or is it wired right. The common from the transformer up to one side of the solenoid. The other wire from the transformer up to the humidistat and a wire from it down to the other leg of the solenoid??


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