Question about Aprilaire 700 Humidifier

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Water not getting to panel when furnace is on

I detected that while my furnace was running, there was no water delivery to the humidifier water panel - that is, the solenoid valve had not triggered. When I moved the humidistat dial to "test/reset", the solenoid activated and water began to flow and continued to flow during the heating cycle. The dial setting was returned to its normal position (35%) during this time as well. During the next heating cycle, however, the same scenario ensued - no water delivery to the panel. I sought some professional advice and was told that there was a high probability that the solenoid was either defective or clogged in some way. I replaced the solenoid valve with a new one (the old one was not clogged in any way and inlet and outlet tubes were both clean as well) and am still having the same issue. Evidently, the problem is not the solenoid but something else. I'm thinking perhaps that the humidistat panel itself may be defective in some way. Any ideas?

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Re: water not getting to panel when furnace is on

I had a problem quite similar to this. It was the power connector. This is the 4-pin white connector that engages when the cover is removed/replaced when accessing the water panel.

One of the pins was loose in the connector thereby supplying intermittent 24 volt power for the solenoid that is powered by the fan motor control board transformer in the humidifier cover next to the fan motor (not seen unless fan is dissembled).

If you are technical such as I am this is easy to fix by removing the connector, removing the loose pin, and often each retaining clip on the connector pin can be bent out slightly, then replace the pin, and then it should be fine. Also, it's best to check this out on a bench while running the entire unit. You also might need to replace the entire power connector. Sometimes it's easy to think the problem is a defective solenoid or fan motor/transformer board, etc. It's frustrating, because sometimes the humidifier works perfectly, and then sometimes there is no water flow. Since I did this mine has been 100% OK.


Posted on Feb 07, 2008

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Re: water not getting to panel when furnace is on

Assuming that your humidistat panel in on the cold air return, I would remove the panel and check that some lint or dust possibly is stuck to the sensor. Also check the operation of the solenoid easily when the furnace is running by turning the dial back and forth and you can hear the solenoid open and close.

Posted on Mar 07, 2007

Re: water not getting to panel when furnace is on

The humidistat detected that the RH in the area of the sensor was as required or exceeded the setting as an upper limit

Posted on Mar 06, 2007

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