HoneywellTH3110D1008 Pro Non-Programmable Digital Thermostat

I ordered this thermostat to replace an older Honeywell RTH1100B model that worked great for years but got damaged by corroded batteries and is now discontinued (why these thermostats do not have an option to run on the 24 VAC system power is beyond me). Since both the old and new thermostats were made by Honeywell, it was easy to install as the wiring hookup was identical.After installation, I noted that the temperature reported by the new thermostat seemed a bit low but I figured it was due to having been in the Amazon delivery van for several hours. I set the temperature to the desired room temperature and the heat immediately came on. I went on to do other things and forgot about it. About an hour or so later, I was feeling quite warm and noticed the heat was still on. I went to check the thermostat and it was still reading a low temperature! The heat was running continuously for over an hour. I immediately shut it off and checked the room temperature. A standalone digital thermometer said 68 while the thermostat said 57. Not good. I put the thermostat in standby and figured I would wait a few hours and see if anything changed. The next morning, the new thermostat now read 52 and the room temperature was 60. Something was definitely wrong. I initiated an exchange with Amazon and a replacement arrived two days later. I installed the new one and it immediately read the same temperature as the digital thermometer so I was happy. I have been using the replacement for four days now and it is working as expected. The backlight is very helpful in low light situations and having both the room temperature and set temperature displayed side-by-side is helpful too. And as luck would have it, the mounting hole locations were identical to the previous thermostat so it was a simple mounting job.As long as you get a properly functioning unit, it should work very well. If not, Amazon's exchange procedure is painless and I was able to get the issue rectified pretty quickly (it was possible to manually activate the heat on the defective unit so I was not freezing waiting for the replacement). I gave the thermostat five stars because the replacement is working very well. I figure the defective unit was a "one off" and not indicative of the overall quality.

This is for the TH3110D1008.It is a one heat stage, one cooling stage non-programmable thermostat. It has the capability of operating a heat pump, but if you have backup or emergency heat, it will not work properly for that. I have never seen a heat pump without backup/emergency heat, so I do not recommend this unit for heat pumps.I have installed this model on all my rental houses, most of them originally had programmable thermostats, and all of which have one stage cooling and one stage of electric heat as they are in SE Florida and as we only need to run the heat for a few days a year it makes no economic sense to install more elaborate heating equipment in this part of the country.It has completely cut out the problems and questions my tenants were having regarding programmable thermostats.I also like this model because it can be powered from the air handler instead of from batteries. I wire these with the C wire, which eliminates the need to use batteries. This also eliminates complaints from my tenants when the batteries die on the thermostat and they do not know what to do. Most people that rent are not handy and do not want to fool with any house problems, no matter how minor.If you have a one stage cooling system with electric or gas/oil forced air heat, here is what you need to wire:Red wire (24 VAC) from air handler to the R terminalBlue (usually, could be another color) wire (common) from air handler to the C terminalYellow wire (cooling) from air handler to the Y terminalGreen wire (fan control) from air handler to the G terminalWhite wire (heat) from air handler to the W terminalExcept for the common wire, the colors above are very common, although your colors may vary. The point is, to wire the R, C, Y, G, and W terminals on the thermostat to the corresponding functions on your air handler. All the thermostat does is connect 24 VAC from the R terminal to the Y terminal when it calls for cooling, 24 VAC to the G terminal when the thermostat is to operate the indoor fan, and 24 VAC to the W terminal when the thermostat calls for heating. It is really that simple.If you have electric heat, the thermostat will turn on the fan when it calls for heat. If you have gas or oil forced air heat, the furnace will very likely have a thermostat that will turn on the fan after the gas/oil flame has heated up the heat exchanger, and once the thermostat heat setting is satisfied, that furnace based thermostat will turn off the fan once the heat exchanger cools down.However, even when you have the thermostat set for gas/oil heat, the thermostat WILL CONTROL THE FAN when it is cooling mode if it is properly configured.A common problem with gas/oil furnaces is the failure of this thermostat, so if you have fan control problems with gas or oil forced air furnaces, you need to check the fan control thermostat in the furnace before blaming this thermostat.Also, depending on the type of heating system you have, besides the electric or gas/oil slide switch on the back of the thermostat, there are a few other settings that you should configure for optimal satisfactory operation. It is easy to do, and the included directions explain what you must do, and this is done by the raise/lower buttons on the front of the thermostat that are normally used to raise and lower the temperature.(Don't confuse this configuration programming with the functions of a programmable thermostat.)If you are replacing a thermostat that uses batteries, and want to power your new thermostat from the air handler, please note that it is possible (likely) that the blue wire (if you have one, and the common wire is usually blue but could be another color) is not hooked up to your present thermostat, and it is not hooked up at the air handler as well. If you want to avoid using batteries, in that event you will need to open up the air handler and connect the blue wire to the common connection in the air handler. The common connection is connected to the grounded metal frame of the cabinet in every air handler I have ever worked on.If you only have 4 wires from your air handler to where the thermostat is installed (because that is all that a battery operated (or older mechanical) thermostat needs to control heating, cooling, and fan), then you will need to run a new wire from the air handler or furnace to the thermostat, install an add-a-wire accessory to trick the system into thinking there is a 5th wire, or just resign yourself to use batteries. Here is a link to the add-a-wire accessory.https://www.amazon.com/Venstar-ACC0410-Wire-Accessory-Thermostats/dp/B01IF3QXMC/ref=sr_1_fkmr1_1?ie=UTF8&qid=1519606131&sr=8-1-fkmr1&keywords=diode+for+thermostat+5th+wire#customerReviewsThe point is to not even install the batteries, since when the power to the air handler is off, the thermostat is useless anyway; why bother with them.The thermostat functions very well. It maintains the temperature to 1 degree of your set point (assuming your heating and cooling equipment has the proper capacity to maintain the set temperature). It will remember the heat and cooling set points -- i.e. when you set the heat set point, and switch to cooling, when you switch back to heating it will remember the previously set heating set point, and it remembers the settings after a power outage.The display is back lit and simultaneously displays the set point and current temperature, and it seems to be well made. I have installed 11 of these with no failures and no problems.