Aprilaire Releases New 8400 Series Thermostat

Aprilaire’s new 8400 Thermostat is a great way to control your heating and cooling system.  It has a large easy to read screen, fan circulation mode for improved indoor air quality and because it’s programmable it will save you up to 30% off your energy bills!  Learn more here.

13 thoughts on “Aprilaire Releases New 8400 Series Thermostat

  1. Jean Pecotte

    PLEASE! I’m trying to register my Aprilaire electronic thermostat. I’ll admit I don’t know much about computers as I’m 87 years old, but I’m trying. I do love my new Aprilaire.

  2. sheri carrigan

    please help me ….i have an aprilaire 8400 thermostat…the message centre said it was time to change the filter and humidifery pad…ive done this but the message is still showing up…..

  3. brad

    Thank you for your comment regarding your model 8400 Aprilaire thermostat. When your model 8400 series thermostat is calling for heat the word heating will be displayed on the screen. This indicates the thermostat relay has closed to send the heat call to your HVAC system. Once the set point has been reached, the word heating will disappear from the display. If heating does not disappear after the set point temperature is reached, please contact your HVAC installer to obtain a replacement thermostat. If heating is not on the display once set point temperature is reached, the thermostat is no longer calling for heat and it would appear to be an issue with your HVAC system. We ask for you to please contact your HVAC installer to have them review the installation and operation of the thermostat and HVAC equipment.

    Thank you for giving us the opportunity to be of assistance.

  4. Gary

    I have the 8400 thermostat (1 in each zone). I hear a clicking noise every time the thermostat kicks on or off.. If this normal, is there anyway I can turn this off? This is so annoying as one of the thermostats is in my bedroom.. I can’t imagine this is a feature.

  5. christie

    I had a new Aprilaire thermostat installed this past winter and it worked fine. I turned on the AC a couple of days ago for the first time since the thermostat was installed and now there is a series of clicks each time the AC starts up and when it turns off. What is this noise? It is annoying because the thermostat is in the hall near my bedroom and I can hear this clicking at night when I trying to sleep. Thanks!

  6. Brad Uselmann

    Thank you for your inquiry regarding the operation of your Aprilaire 8400 series thermostat. Whenever there is a need to run the cooling or heating system in your home your Aprilaire thermostat closes a switch inside the thermostat. This allows the signal to be sent to your HVAC system to turn on the cooling or heating. The closing of the switch will make an audible sound but it typically isn’t very loud. Most thermostats use the same type of switch. There may be a sound resonating from the HVAC system when the cooling turns on as well. Your HVAC installer should be able to determine the origin of the sound. If it is your Aprilaire thermostat, your HVAC installer could re-locate it to another area where the sound wouldn’t be as noticeable.

    Thank you for giving us the opportunity to be of assistance.

  7. kurt

    I have NO display on my 8400. Changed the batteries, pushed the reset and still NO display. What do I do next?

  8. Will

    Thank you for your email regarding the Aprilaire model 8400; If the display is totally blank with new batteries the 8400 thermostat may have experienced electrical short or lightening surge, the 8400 will then need to be replaced.

    If you have any further questions regarding this or any of our products, please feel free to contact our customer service department at your earliest convenience.

  9. Neal Maher

    New Aprilaire 8400 Thermostat installed recently in connection with a new heating & cooling system. Is there a way to recalibrate the temperature displays, both inside and out. Inside reading is always 1 or 2 degrees higher than actual temperature as verified by several digital thermostats I have in the house, even when I place them right next to the thermostat. Of greater concern, the outside temperature display is always 5 or more degrees off, sometimes lower, sometimes higher. For example, this morning it was -8 degrees outside but the sensor was reading +13, a 21 degree variance. This is of real concern as an accurate outside temperature is required to activate the heat pump efficiently.

    1. aprilaireadmin

      Dear Neal,

      Thank you for contacting us about your Aprilaire model 8400. The indoor temperature displayed on the 8400 can be programmed to match another control when adjusting the offset in program screen 03. Please refer to page 13 of our installation instructions for adjusting the offset. 21°F difference then actual outside air temperature in the morning may indicate that the sensor is located in direct sunlight and then needs to be relocated per instructions on page 4.

      If you have any further questions regarding this or any of our products, please feel free to contact our customer service department at your earliest convenience, 1-800-334-6011.

      If you do not have the manual, one can be downloaded at http://www.aprilaire.com/owner-center/owner-center/owners-manuals


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