How do I know if my Model 700 humidifier is working?

Friday, December 17, 2010 by Aprilaire Team
Consumer question:

Right now the outdoor daytime temp is about 40 degrees, the indoor temp is 70 degrees and my indoor humidity guage is registering 20%. Last year when the outdoor temp was about 10-15 degrees and I had adjusted the humidity control for that temp, the humidity stayed about 10%. When I first turn on the humidfier in the fall and with my somewhat loss of hearing, I usually don't hear a click (per the manual)to set humidity. Am I adjusting wrong? Should the furnace fan always be on even when the furnace itself is not producing heat? Is humidity only created and dispersed when the furnace blower motor is on?

Aprilaires' response:

Thank you for contacting us. To test to see if the humidifier is working properly you would need to have the furnace running. We recommend turning the heat up about 5 degree to make the furnace run for a couple of minutes. You would then go to the humidistat and turn the dial to test/reset and the solenoid would open and water would flow into the unit. Test/reset can be either past 45% as far as it can go. If your humidifier is a tan 700 humidifier, the two brown wires are live with 24 volt 10VA coming from them. One way to test to see if the solenoid is working is by carefully touching the two brown wires together which would open the solenoid and allowing water to enter the unit. You should be able to see the water flowing out of the drain hose.

Depending on how the humidifier was installed on your furnace, would determine whether the furnace fan needs to be running to make the humidifier work whether the heat is on or not. Usually the humidifier runs when the furnace or furnace fan are running. You would want to follow the wires leading from the solenoid to determine where the humidifier is wired into.

You might want to have a local dealer to come and service your humidifier to make sure it is working if you any other major issues. We are available at 800-334-6011 to help you troubleshoot further with the unit.  If you do not know who your local dealer is you can find one by using the dealer locator on

Comments for How do I know if my Model 700 humidifier is working?

Friday, December 24, 2010 by Janet Crowther:
We have had our humidifier serviced about 5 times this year and each time they come out they find something else supposedly wrong with it and fix it. I have turned the humidistat up to maximum humidity and we never get water on the windows - which I figure is how I can really tell if it is working. Is this an adequate test or is there some other way that I can tell if it is working or not? Thanks!
Monday, March 31, 2014 by Henry:
I recently had the Aprilaire 700 with Humidistat 60 installed. The humidistat's Blower Activation Switch is set to ON and everything seems to be working. However, when the furnace is about to shutdown, the humidistat cycles the power and starts up with r1 and then back to normal RH setting. Is that normal for the humidistat to cycle power or is it a wiring issue? Should the humididstat always be on (showing the RH%)? Please let me know. Thanks!
Monday, March 31, 2014 by Brett Phillips:
Dear Henry,
Thank you for contacting us with regards to your model 700 Humidifier. Based on the information provided, it would seem that your control either has not been wired properly, or the power that’s provided to it temporarily shuts off. The r1 code will show up under two conditions. One is when the control knob is placed in the Test/Reset position for more than 1 minute. The other is when the control is first powered up. We would recommend that you contact your installer and have them verify the wiring and the power source in particular.
We appreciate the opportunity to be of assistance.

Leave a comment