Honeywell Home CT87K1004 The Round Heat Only Manual Thermostat,Large,White,Large

Had old 70 yr old type thermostate with mercury switch replaced it with this. It only had 2 wires a white and purple. According to instructions the white wire connected to r terminal and the purple to the w terminal. Been testing it out And seems to control the gas home furnace correct. To my surprize it went better and easier than expected.

Easy to use and easy to install.

POS!!!!! DO NOT BUY THIS!!!!! I bought one, followed the instructions and installed it. Seemed simple. Didn't work, ok, it faulty, returned it for another one. Didn't work. Went to the local hardware store, bought the same model, didn't work. Honeywell is not the same company of 50yrs ago and sells crap. Installed another brand and works perfectly. My system is gas, steam heat only. Two wires. The old unit is Honeywell from 50yrs ago, murcury system. Should be simple, do better Honeywell.

It works well. This is a nice improvement from the old mercury switch models.

See the review by John, 2-17-13 for an explanation of the (rare..) use of the 10+ year-life battery inside, as is there to 1) reset after a power failure and 2) initially after install: to charge up a capacitor which actually feeds the internal electronics and which is constantly replenished by the 24-28 V. AC power delivered usually by the furnace electrics when its own power is on (24/7.) Those 24~28 Volts A/C come via a small step-down transformer usually located within the furnace box. That said, recently I did have an -87K unit fail after some 4-5 years (I have no *reliable* info on the failure rates on the hundreds of thousands of these units in service, and individual guesstimates are useless/just gossip.) As I “do electronics” I naturally performed a necropsy on unit. The nominal 3 V battery in that was near-new at 3.22V on a Fluke prof. meter; it did not die via “battery failure”—see above, again—the few occasions where its small power input would actually be missed. I still wanted the natural simplicity of the glass-sealed mercury capsule, but I do realize that the mission of a thermostat/in 2018 is trivial to design and I Saw that the circuit board in my failed unit is comparable quality to that seen in prof. grade test equipment: so I was just unlucky in this early failure (most failures happen on initial turn-on, then ..during first days/weeks until: they go a long….time and then fail for complex reasons.) Four or so years IS … unexpected. Hence the 4-stars, pending.. I just bought another -87K unit from Amazon. It was a 3-second “drop it in and carefully press down till it latches” operation (no wiring had to be done.) I left it alone with temp turned all the way down for 5 min. or so: letting that capacitor charge up to its working voltage from the battery. While it’s only been a couple days, it is doing exactly what you want it to do: silently switch on the permission for furnace to take over. Note that: the manner/temperatures at which the furnace decides finally *to turn OFF* its blower motor is Not anything to do with the thermostat’s ON/OFF decisions: a variety of means are engineered within furnace controls to cover this so-called “hysteresis” time + temp process. Your thermostat is an ON/OFF switch ONLY. I’ll drop in and modify this report should this new unit fail shortly (unless, of course: many are already in caves, say? No reports then. No furnaces either.)

Easy to install work great very happy

AOK

Great

très pratique pour personnes âgée

It fit and worked correctly

We bought this in the spring for our shop but then it got nice out and we never installed it. Fast forward to fall, installed it….but then the furnace wasn’t working. Called a repair guy, he was thinking it was the valve on the furnace, tested, not the valve, tested the thermostat and its thermostat that doesn’t work. Yes our fault for not figuring it out sooner, but yeah wasted a lot of $$$$ both on the thermostat and on the plumber.

after having two digital thermostats only worked half the time I now get my but up an adjust the temp my self

Bought 2. One works fine, the other has been replaced twice.