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 terminal
Blue (usually, could be another color) wire (common) from air handler to the C terminal
Yellow wire (cooling) from air handler to the Y terminal
Green wire (fan control) from air handler to the G terminal
White wire (heat) from air handler to the W terminal

Except 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#customerReviews

The 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.

This is an outstanding product, perfect for an installation in a simple HVAC system where detailed programming is not required. It is extremely easy to install, even for an unsophisticated person. Only tools required are a small drill and a screwdriver. Optional is a level. On iPhone, there is a built in "level" on the Compass App. The only critical thing is to record the wiring with respect to the terminals on the original installation, and to reproduce those on this product's terminals. Important: Use the terminal designation, and NOT the wire color which may vary depending on the installation. If your original installation has a "C" wire, this thermostat will not require batteries, although they can be installed for backup in the event of a power outage which is really not important because if that occurs, there will be no line voltage to operate the fan motor of the furnace so that you do not want to ignite your furnace's burners. If your installation does not have a 24 volt line(C), you will need batteries.

The unit comes in two parts which click together. The back part, or the face plate is the one you install on your wall with the hardware provided, and onto which you affix the designated wiring. After this is completed, you just "click on" the front part of the unit which receives its power from juxtaposed contacts on the faceplate. It's that simple.

The display on the unit is easily viewable in large numbers, which consists of both the ambient temperature, and the preset temperature which is adjusted with two buttons(up and down) on the right side. The illumination is not permanently lit, mainly to conserve battery power, but can be turned on by merely pushing briefly on either the up or down buttons. It is an LCD display on a bright yellowish-green background and quite attractive.

I've had my unit for about 6 months and it has been very reliable, and accurately heats or cools exactly to preset temperature. If your usage pattern consists of adhoc, by hand, quick adjustment of temperature when in the house, day/night, and away, and don't need a more complicated, programmed method of usage, this is the unit for you. It is a waste of money to buy the more expensive versions that allow the more advanced usage patterns. Honeywell is a tried and true company in the field of HVAC thermostats, and this item will not disappoint.

No conflict of interest with this company!

BOTTOM LINE: UNQUALIFIED BUY for the appropriate user.

Works as expected. Hopefully this unit will outlast its predecessor, which was programmable. We purchased this because programming was not always executed as programmed. So we like the idea of manual operation. Biggest loss with this step-down is the lack of an automatic transition between heating and air conditioning, but I knew that going in.
8/28/17 Update: Very pleased but took back a star in my rating because the loss of automatic switching between heating and air conditioning seems it will be a fairly negative thing and to my way of thinking that could have been designed in easily and cheaply.

This was super easy to install...the only thing I didn't understand is the metal jumper piece that was in the RC and R slots. I had an RH connection in my old thermostat so figured the R would be the correct position in this thermostat. Well, it IS, except I had removed the metal jumper piece because my wire went to R. During my test, the heat turned on, but not the air conditioner. Turns out you have to keep the metal jumper in, along with your R wire in order to make the connection to the other unit. I figured I didn't need it because I didn't have a wire in the RC of the old thermostat. Worked like a charm once I got it back in. Love the simplicity. Feels solid too. I didn't like the slider bars under the unit I had---the buttons on the face of this one are much more substantial feeling when you slide them back and forth.

No frills and performs exactly two functions (heat on and off)...just what I wanted. The build quality is okay. Feels like cheap plastic and depending on how often you need to replace the unit's batteries, I can easily see the casing cracking (or breaking) at the hinges. Don't expect more for what you are paying here - sub $30 thermostat. The display is easy to read with a backlight screen. The information displayed includes the actual temperature (the larger number displayed) and the desired temperature (smaller number displayed in the upper right hand corner).

I'm not an electrician, but the unit was easy to install (thank you YouTube for the numerous tutorial videos).

For as many people who want the newest and greatest technology and functionality, there are still those who want nothing more than a simple on/off thermostat. This is that simple option. This item is a definite go.