HoneywellYTH9421C1002 Visionpro IAQ Touch Screen 7-Day Programmable Thermostat, Version 2

I bought this thermostat to replace my mercury lever style on my heat pump system. NOTE you will need 3 wires to interface the thermostat with the relay box unit. I used 3 of the existing 5 wires on my setup and just taped up the other 2. The instructions that came with this thermostat aren't very good... it shows you what would go where but just looking at the relay box unit would tell you that much... Mine did not come with programming instructions either... I had to use Google to find out how to program the thermostat to work with my heat pump. All said and done I am happy with the performance.So why would one buy this? If you have a simple heating and cooling system you aren't going to recoup the cost. However if you require a smarter thermostat because you have a complex HVAC system this thermostat will do the job. You can interface many heat sources and program the thermostat to use them the most efficient way possible. You can hook up stages for cooling also. The thermostat has options to hook up humidifier, dehumidifier, vent fans, and remote temp sensors. I wish it came with the outdoor temp sensor... turns out it is almost necessary if you have an electric heat pump so you don't burn it up when it is below freezing outside.

I'm a technician and installed this thermostat in about a half-day installing additional wiring for the EIM. You have to do your homework first before installing to be certain you understand the proper wiring connections to the EIM compared with the old thermostat. You have to know your system, especially when you configure this thermostat.Unfortunately, there seems to be a bad contact in the EIM that causes the aux heat to intermittently turn on. When aux heat displays on my thermostat, I sometimes have to apply light pressure to the EIM box for example, to get the aux to turn on. This is a bad problem to have especially with the recent extreme cold weather where aux heat is necessary. All wiring connections tight. I will have to de-install this unit and exchange. Not happy.The box was not in new condition either. The EIM in the box was not wrapped like the thermostat - Hmmm.

Very nice product that controls all my air quality equipment & furnace: ERV air exchanger, humidifier, and of course the furnace itself. The unit can be programmed to run the furnace fan (air handler) in conjunction with the air exchanger and will also control the humidifier to turn on in several ways (only when furnace heat is on, any time regardless of furnace heat, with and without running the furnace fan). This unit will also circulate air throughout the house on a random timer basis to keep the air fresh when heat, humidity or air exchange isn't called for. Very nice unit. Fairly easy to program. Only complaint (the reason for 4 stars instead of 5) is that the LCD panel does not show when the individual air appliances are running (i.e., no indicators for air exchanger, humidifier, air circulation or even when it calls for heat from the furnace).

I bought this to use on my new York furnace and a/c. I have the thermostat on the upper level and I have a remote(wired) temp sensor downstairs in the nursery. After a couple of weeks I noticed that my house seemed a lot colder than it did with my old system and vintage Honeywell thermostat so I had the installer check the thermostat and remote temp sensor. He discovered that the remote sensor was accurate within .5 degrees, but the thermostat read 4 degrees warmer in heat mode and two degrees cooler in cool mode than either of his devices. While this is great if you want to save money on your bills, it's awful if you want to be comfortable. The thermostat has a temperature offset feature, but if you set it two degrees warmer the cool setting will be 4 degrees off and vice versa(sp?). I had this thermostat for 3 or 4 months before I had it installed, so I couldn't return it for "satisfaction" reasons and it the warranty doesn't seem to cover accuracy. I'll probably end up installing a remote sensor right next to the thermostat and use it as the temperature sensor.I do like some of the features of this thermostat, it has worked very well with my York Affinity modulating furnace. It has "learned" the ideal heating and cooling cycle lengths to maintain our house at the temp it does read and the "circulate" feature is absolute genius.I wouldn't recommend spending more on this thermostat if you're expecting it to be worth the money.

The EIM still worked but eventually this failed. If you buy the new one be warned. It reminds you to replace the face plate behind the thermostat. But it doest warn you to watch if the order of the wires had changed. Back of the new thermostat shows first is dats and second two are R and C. Originally it was R, C, Data on the one I previously has.. It just calls them 1,2,3 and isn't tricky unless you figured it was the same which it may not be.I hope the new one lasts longer. Has good humidity control including frost control if you have outside thermostat option.

Awesome! Tons of features and programing capabilities ... I had to put a humidifier in my new house and just put this same thermostat in my old house so I knew what I wanted. I found a HVAC guy who installed it all for me in a couple of hours and saved a bit of money since I bought the stuff .. only thing they couldn't cover it if it broke but I have a warranty anyways right? lol You will like it and can add more features later if you want to.

Good quality, not easy to wire tho. But if do a little homework online and read the instruction, you can pul it off

Works great. We had to replace the prior version as it stopped working. The screen is easy to read, the programming choices on screen are intuitive (I am a non-mechanically inclined woman) and it keeps the house warm when we want it and cool when we don't.