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Honeywell THM5421C1008 Automatic or Manual Changeover, 4H/2C

SKU: 376389

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About the Honeywell THM5421C1008

Honeywell THM5421C1008 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 # THM5421C1008
Weight 19.00 lbs.

Product Features

  • Advanced dual-fuel control.
  • 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.


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


The possible cause for this problem is that the Compressor minimum off timer is active. You can wait up to five minutes for the cooling or heating(heat pump) equipment to turn on. You can refer here for more information. Thank you for visiting our website!


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You can contact our customer service hotline at 435-868-4020 for more information about the Honeywell THM5421C1008 Automatic or Manual Changeover, 4H/2C. Thank you for visiting PlumbersStock!