Honeywell Nonprogrammable Heat Only Thermostat, White, 1 Pack

Easy to install Bd works great. I use it for my gas fireplace

Easy to hook up and works flawlessly. Great buy if you need something just for heat.

This Honeywell TH1100DV1000 Pro Digital Heat only thermostat replaced a more than fifty year old General Controls brand model T-80 analog thermostat that wasn't reliably controlling an old natural gas "gravity" furnace. The old analog thermostat wasn't reliably turning the furnace on or off. It would often fail to turn off the furnace within a reasonable range of the set temperature. More often than not it would fail to turn the furnace on at all regardless of the set temperature. The natural gas furnace and the thermostat had been serviced and checked several times in the past by a HVAC technician who indicated that everything seemed to be working ok but for whatever reason my experience was that it was not reliably turning on. Before I removed the old analog thermostat I used a digital multi-meter to read the voltage and polarity of the heat only system and used red and white colored electrical tape to wrap and mark the two wires. I measured 450 millivolts DC and marked the positive side wire as red and the other wire as white. I removed the old vertical shaped metal cased thermostat and this new vertical digital thermostat back plate fit exactly over where the old thermostat had been so I did not have to paint, patch or cover any unsightly difference for the new thermostat wall plate. I was also able to re-use the older wall plate screws to mount the new wall plate. I did notice that the hole behind the thermostat wall plate was a few inches high and and inch wide. I had read that a large hole behind the wall plate can cause cold wall drafts that can negatively effect thermostat temperature readings. I used strips of thick extra sticky Gorilla (restricted trade mark) brand tape to cover that large opening and cut small holes for the two wires and wall plate screws. I connected the two wires to R for red and W for white (C was not used for my two wire millivolt system) onto the wall plate wire junction according to the simple instructions provided in the new thermostat booklet, placed the included AAA batteries into the new Honeywell thermostat (required for a millivolt heat only system) and I pushed it over the plastic wall plate. I left the new digital thermostat's advanced settings as default. I turned the simple switch to Heat On and set a temperature for testing. The final result is that this new Honeywell digital thermostat is working perfectly. The natural gas furnace turns on and off when it should. The furnace now cycles as needed to maintain the temperature within one degree of the set temperature. It doesn't overheat or under heat like the old analog thermostat used to do. I really like the minimalist non-programmable, single switch, heat only design. The only decision I had to make was what temperature to set on my new digital thermostat. In conclusion this is an excellent choice for anyone looking to replace newer or older two wire heat only analog thermostats. Notes: I purchased this thermostat from Filter Pro, Fulfilled by Amazon. Filter Pro was great.Their delivery was fast and on time. I ended up changing the cycle rate in the advanced settings mode (using the simple directions) from the default of "5" CPH to "4" CPH. The cycles per hour setting or CPH tries to adjust how many times the heating system is supposed to cycle on and off every hour. CPH is usually optimized for each type of heating system to improve the heating efficiency and energy usage. Even analog thermostats utilize a type of predictive CPH setting. For many basement gravity heating systems in larger homes the CPH recommendation can be as low as "1" or "2" because older gravity heat systems usually require a longer time for the entire system to heat up and for the heat to dissipate into the entire house. However it depends on the size of the home, size of the gravity heater system, how well the home is insulated, seasonal cold outdoor temperatures, etc.. For my smaller and poorly insulated one story home with a smaller gravity heat system a CPH of "3" or "4" seems to work best. You can refer to the included instruction booklet and test what setting works for your home (it's very easy to change it) or contact Honeywell or your local HVAC technician for recommendations on the CPH setting for your home and heating system.

Bought this for my Travel Trailer. It works great compared to the old mercury switch model. A few degrees off but that is not a big issue. Even though it is not designed for 12 volt system, it does a great job. This is second season for it and still going strong.

Exactly what I needed: I have an external-vent gas heater which generates a millivoltage using the pilot heat. This battery powered thermostat gives accurate temperatures and heating control. Works great. Price was right.