As of April 14, 2015 the manufacturer discontinued the Honeywell YTH9421C1010 thermostat. It was first introduced March 30, 2009 and quickly became a very popular thermostat. The YTH9421C1010 was what they call a communicating thermostat.
Communicating thermostats can operate with fewer wires and are proprietary, meaning that they are the only thermostat which can be used with the interface that connects to the furnace. I’ve never been a very big fan of proprietary products, especially things like thermostats.
Proprietary products leave you little option when you want something different or a failure occurs. If that failure occurs or I should say when it occurs you have little option other than purchasing the same part and usually at much higher prices. You cannot add a generic thermostat to a system that requires a proprietary thermostat.
Non-communicating thermostats contain switches that operated the different functions of a furnace, like the blower. or heat. Communicating thermostats connect digitally to a circuit board in the furnace and operate in more of a binary or computer like fashion.
Can I Replace My Honeywell
Also with non-communicating thermostats you have more options to install most any kind of stat you find interesting. My personal preference is the Honeywell 8000 Pro Touchscreen with WiFi. It’s not called a communicating thermostat but it communicates to the internet and gives you a readout of your local temperature and humidity.
If you are replacing a communicating thermostat like the YTH9421C1010 you may have to remove the device that the YTH9421 was communicating to and be sure your controls can be operated by a new thermostat that is a non-communicating stat.
The specific description and model number for this Wi-Fi stat is Honeywell TH8321WF1001 Touchscreen Thermostat Wi-Fi Vision Pro 8000.