HoneywellHome CT87K1004 The Round Heat Only Manual Thermostat

Work good. Just buy it, you need it.

Why did you pick this product vs others?:Works

This style was installed in my grandmother's house for twenty plus years. It seemed like the temperature was off after remodeling and the unit being off the wall for 2 years. I bought the same kind and was able to take the face of the new one and install it with the wiring and base of the old one. Very easy installation, keeps temp great now. Easy to use.

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.)

Works great

THIS HAS A SECRET NONREPLACEABLE BATTERY. It is NOT mechanical. It looks mechanical and feels mechanical, and you think it seems indestructible, but it has a digital board and a battery. That's right! They quietly swapped their trusty old mechanical model for a worse more expensive design. Enshittification? Even if it works out of the box, which two of mine did not, it will fail after 5 years because of the secret button cell battery. Testing with a continuity meter, my first was stuck on, and the second was stuck off, out of the box. I feel swindled. I was looking for a dead simple design for backup heat, but obviously this is far too unreliable for anything called "backup". If you're here, the one you probably want is the Emerson M30 Heat Only, here https://www.amazon.com/dp/B00874D4IG which is your classic bimetallic coil and literally can't fail.

This have to be the simplest thing ever? I never ever in my life change a thermostat and it literally took me 5 minutes the best product ever! Real talk

I like this manual thermostat. I have one that I have no idea how to program, and wind up doing it manually every day according to the temperature and humidity. I don't want an automatic thermostat, this is impractical in my house! So, I look forward to this one, simple and practical. And looks nice.