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Honeywell YTH9421C1010 Automatic or Manual Changeover, 4H/2C

SKU: 380645
Save 57% · Retail: $601.68

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About the Honeywell YTH9421C1010

Honeywell YTH9421C1010 Automatic or Manual Changeover, 4H/2C. This VisionPRO IAQ touch screen universal programmable thermostat offers electronic control of 24 Vac heating and cooling systems. in addition to humidification, dehumidification and ventilation all with just 3 wires to the thermostat. VisionPRO IAQ Total Home Comfort System.

Product Details

Manufacturer: Honeywell
Mpn # YTH9421C1010
Weight 2.00 lbs.

Product Features

  • Advanced heat pump control featuring balance point
  • Large, clear display with backlight shows the current and set temperature and timeeven in the dark.
  • Three wires to the living space allows for easy equipment upgrade without having to run additional thermostat wire.
  • Thermostat connects with Equipment Interface Module or EnviraZONE panel to control temperature, humidification, dehumidification and ventilation from a single point in the home.
  • Automatically raises humidity levels throughout all rooms in the home, moisturizing air to prevent symptoms of dryness and to protect hardwood flooring and woodwork.
  • Removes air pollutants by exchanging the stale air in a house with fresh, filtered air better than having an open window.
  • Vent on demand and automatically using patented advanced ventilation control
  • Controls ventilation with other HRV, ERV, or Freshair damper.
  • Controls dehumidification using air conditioner with high or low speed fan or a whole house dehumidifier.
  • Controls humidification to increase homeowner comfort while protecting woodwork and furnishings
  • Various Hold options allow you to override the program schedule, as desired.
  • Change/check reminders let you know when to service or replace filters.
  • Real-time clock keeps time during power failures and automatically updates to daylight savings
  • Touchscreen interaction


4.5 out of 5 rating is our rating for, we got that rating because we have lots of experience and great people with expertise in plumbing. BUT WE WANT YOUR HELP. This product doesn't have any reviews yet, and we don't want to write our own reviews. It is more valuable to us that the customers get to share their experience with our products. Please, if you have any experience with this product, take a moment to share and help someone else who is trying to make a decision. Thank you!

Questions & Answers


Thank you for visiting We appreciate you asking for help on our Honeywell YTH9421C1010 Total Home Comfort System. Here are the steps to unlock the screen: 1.Press and release the System Key. 2.Press and hold the two blank keys on either side of the center blank key for around five seconds until the screen changes. 3.Release the two blank keys when the screen on the thermostat changes. 4.You should then be able to change the settings as desired. If you wish to see how the keys and the screen should look like, please check the Installer Setup Section. on page 12. Thank you for shopping with – the perfect place to find high-quality products at low, low prices!