Question about Aprilaire 400 Humidifier

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Keep blowing 24V transformers

I believe I wired this correctly according to Aprilaire's "New and Improved Wiring Diagram" that came with the product. The humidifier cuts in properly when the furnace goes on calling for heat, but the solenoid did not open to let water flow and I blew out the 24V transformer. I got a new one and first wired it directly to the solenoid and the water flowed properly. The instructions for the unit says to wire the yellow wires from the solenoid along with the white wires from the float switches. When I first did that the float switches seemed to work in reverse of what they were supposed to do, i.e the solenoid did not open unless I lifted the floats. When they were in their normal down position the solenoid did not open. In addition, after a few minutes of running that way I blew out my second transformer. I had one wire from the transformer wired directly to one of the H terminals on the ADHC. The second wire went to one set of yellow and white wires from the solenoid and the float switches. The other set of white and yellow wires were wired to the second H terminal. That sure seems to be what their wiring diagram calls for. Why is this not working properly and why am I blowing transformers?

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Somewhere in the mess you have described there is a short that is compelling the transformer to put out more current than what it is designed for. It gets hot, really overheats, insulation melts, and the wires melt. Ergo blown transformer.Problem is with whatever that unit is plugged into/powering..

Posted on Mar 03, 2017

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Posted on Jan 02, 2017

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SOURCE: Humidifier control .

if humidifier was wired into thermostat circuit for power instead of seperate transformer , this can happen. you need to see if you voltage going to the solenoid valve. if you do , and it isn't opening, the valve is bad . this is assuming that it is using a # 50 relay to come on only when the fan runs . . make sure the water valve is open

Posted on Dec 28, 2007

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1 Answer

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Is Aprilaire 500M suppose to turn on when furnace motor turns on?


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Jan 13, 2013 | Aprilaire Humidifiers

1 Answer

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1 Answer

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robhvac47_20.jpgSail switch

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1 Answer

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Feb 07, 2009 | Aprilaire Humidifiers

1 Answer

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1 Answer

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