HoneywellTH1100DV1000 Pro-Digital 2-Wire Heat Only

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.

Just replaced the thermostat in my RV travel trailer with this one. Works perfectly. I just needed it for heat no a/c. My a/c is controlled on the a/c itself so this was an easy install. Threw away the Dometic piece of junk.

These function well - and as advertised. They are for a simple, two-wire heat only system. Basically start/stop. Very accurate according to my recording thermometer. We got these for the ability to go as low as 35deg F, which you have to set via menu because the default is 40. We use in garage to keep things just above freezing. These housing case and cover are somewhat fragile plastic, so be a little careful with install and it’ll be fine.

I bought this to replace the 2-wire analog thermostat that came on my RV. Took about 10 minutes to install. It’s cheap and basic, which is all I needed. Build quality is okay, I wouldn’t trust it to hold up to someone bumping it hard with something, but it’s good enough for what it is.

A new gas heater was installed in my apartment that used a bi-metallic thermostat as the controller. It was a simple setup which used a thermopile heated by the pilot light to generate a voltage to operate the gas valve. This is a two wire system. The bi-metallic controller is adjusted by pushing gently with a finger to move a pointer over a temperature scale, its crude but it does work. I will admit I am spoiled in this digital age, and I much prefer a digital readout, but there is the problem that the reason a bi-metallic thermostat was installed to begin with, was because a thermopile only puts out millevolts. This is too low a voltage to operate a digital thermostat controller. I found this Honeywell thermostat on Amazon, it uses batteries to operate the digital readout. I bought it and am extremely pleased with it. It was easy to install and works perfectly. I now have a digital thermostat with a read out that I can set as I please, definitely a five star purchase.

Excellent product, easy installation, flawless functionality

Replaced our Suburban old-time thermostat with this unit. Easy swap, works great, far more control over the temperature now. Backlight is an additional plus!