How do I know if my Aprilaire humidifier is working?

Friday, November 25, 2011 by Aprilaire Team
Consumer question:

I just purchased a house which has an Aprilaire Automatic Humidifier Model 600 installed. How do I know if it's working? The control panel has an OFF position and the different humidity levels, but there is no light indicating if it is ON or not.

Aprilaires' response:

Thank you for contacting us with regards to your model 600 Humidifier. When your heat is on and the humidistat (control panel) is set to a level higher than the current level of humidity in your home, the humidifier should be on. The easiest way to verify this is to look at the drain line of the humidifier. During normal operation, model 600 will have a small trickle of water draining from that line. If the humidifier is off, or if the furnace is off, there should be no water draining from that line. Depending on the age of your humidifier, you could have any of several humidistats installed. You can find the owner's manual for all of the 600s released since 2001 online at

We appreciate the opportunity to be of assistance.

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

Monday, November 12, 2012 by Chris:
How can I set the Aprilaire 110 so that it comes on when the furnace is running so I can confirm that the water is flowing and the unit is operating?
Thursday, February 14, 2013 by tracy:
have model 600 aprilaire humidifier when heat is on should water always be running through filter? if water is not always running what could be wrong? when put on test/reset the water runs, when turn the dial to a number setting, water stops house feels dry
Saturday, November 16, 2013 by SAB:
Aprilaire Humidifier (Model 600): When I turn the dial setting knob, the screen does not display the number I am turning to, it only shows the Hunidity %. [I have two units, and the other unit displays the number]. Is this a problem that I can correct, if not, is it an issue that needs correction. Thank You.
Wednesday, November 27, 2013 by brad:
Thank you for your inquiry regarding the operation of your Aprilaire humidifier control with your model 600 humidifier. Whenever the dial on the control is adjusted the display will initially show a number of 1-7 corresponding with the dial setting. This only lasts approximately 5-10 seconds(this is how it is designed to function) . Then the display will only show the relative humidity the control is currently measuring as a percentage. The control will operate your humidifier anytime the indoor humidity drops below the desired level. As the humidity level changes the humidifier control will show the current humidity level as a percentage. Based on the information you provided, it appears your controls are operating properly.

Thank you for giving us the opportunity to be of assistance.
Sunday, December 15, 2013 by Dan:
I have an Aprilaire 600A. The display backlight works, however no numbers show up on the display (shows a blank screen, even when adjusting the dial). The unit itself functions properly, turning on with the furnace, and a small trickle of water can be seen coming from the unit. All appears well except for the display. Is this a known issue?
Wednesday, December 25, 2013 by savitri khanna:
My Aprilaire has similar problem as mentioned in December 15 post.
The display backlight works, but no numbers show up on the display. It only shows % sign but no numbers are displayed.
Thursday, December 26, 2013 by Kevin:
Dan an Savitri,
The control may continue to work just fine but not show the level of humidity. The humidistat would need to replaced through the installing contractor or back through your point of purchase.

Thank you for giving us the opportunity to be of assistance.
Monday, January 6, 2014 by Robert:
Does not seem the Humidifier is getting water into it, how can I solve this problem.
Friday, February 7, 2014 by Andrea:
I have an Aprilaire 700 series. It was installed 2 years ago. We just changed the water panel last week because the control panel was blinking yellow. The control panel says that it is a model 60. The relative humidity in the house now is 25% and still very dry. We have the knob turned up to 7--all the way--and the humidity level is not changing. When the furnace runs we do hear that trickle of water down the sewer. Why does it seem like the system is not working. The humidity has been around 25% for most of the winter. We thought it was due to that yellow flashing light. Any ideas?
Tuesday, February 11, 2014 by Phyllis:
Thank you for contacting Aprilaire.

The way to know if your humidifier is on, is the fan inside the humidifier will be on and you will have water coming out of the bottom of the humidifier.

When the yellow light blinks, it is just reminding you to change the water panel. It needs to be changed every year.

This light, however, does not even know if you have a water panel in the unit. It is only a timer. When you do change the water panel, you should reset the timer.

The #60 control can be used as automatic or manual. If it is automatic, then it may have been doing what it was designed to do.

When in automatic mode, it is using an outdoor temperature sensor. It is keeping note of the outdoor temp for you, so you don’t need to worry about what the outdoor temp is. When it gets colder outside, you may want to turn down the level of humidity in your home. Being in automatic mode, this does the job for you.

Of course this winter has been much colder than normal across the county. Many, many people have noticed that RH levels have not been as high this year as they have been able to maintain in previous years.

The reason we set back the RH levels in colder temps is to avoid getting moisture on the windows. That would mean that there also is moisture building in your exterior walls. No one wants to get mold or rot there!

As long as it runs every time it can, then the levels will come up soon as the temps come up.

Please let us know if you have any further questions.
Sunday, March 9, 2014 by christi Conner:
I don't know what number to keep my dial set on my april air. don't you go by temp outside. I don't have my manual' I would like to know what number to set it on in regard to temp outside...thanku

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