round white honeywell thermostat

Hi,
I have a Keystoker 90 and the round white thermostat, I noticed when I unplugged the stat from the mounting base that there is a small button battery in it. What is the purpose of this battery and should I change it every few years? What happens if the battery weakens?

Is it digital? Not sure, most of the the standard round Honeywells, just ahve a switch in them. I updated mine to digital. Maintains well. But, I would think change it every year or so

No, it's not a digital. What type of digital thermostat would work with the keystoker? I don't have the coal-trol unit. Is there an advantage to the digital over the analog?

Any digital thermostat would work. It's basically an off/on switch. I have a cheap LUX from ValuHomeCenter with my keystoker.

Seems to maintain a bit better, then if you want a setback (1 or 2 degrees only), you could set it up or down at certain times.

Beware of some of the cheap digital setback thermostats. One model, (can't recall), when the battery went dead, the thermostat goes wide open. People have returned home from small vacations and found their house 90* and wallpaper peeling from the walls. A google search should find those interesting stories. Might be Hunter brand? I hate Google search anymore, they have totally sold out to advertisers and spammers.

WNY wrote:Any digital thermostat would work. It's basically an off/on switch. I have a cheap LUX from ValuHomeCenter with my keystoker.

Seems to maintain a bit better, then if you want a setback (1 or 2 degrees only), you could set it up or down at certain times.

So any digital therm for like an oil furnace? I have digital therms for my electric baseboard heat and I don't think those would work for coal stove as they get wired direct to power, there are no batteries. I'm thinking about going digital, especially if it maintains better. I imagine they are more precise and sensitive to temp fluctuations than analogs?

I am not familiar with digital thermostats but to work well a thermostat has to be more than an on off switch. It also has to contain heat anticipation which consists of a small heater that causes the thermostat to turn off before the room reaches set temperature. This is to prevent overheating the room which would happen without the heater because there would still be residual heat left when the heater shut off.

The thermostat has to be matched to the transformer that powers it and the heat anticipation should be adjustable. Otherwise you will get wide fluctuations in room temperature.

I think the electric baseboard thermostats are different. But, I would think any of the Standard/Digital ones that run off 24VAC should work.

I have been running a basic Hunter programmable since yr. 2 with my Keystoker. No problems whatsoever. It not an anticipation model but hold the temps very well. I very rarely get more than +/- 1' of set temp. On a VERY cold night I may see +/- 2' but that only happens once in a while. I can live with that. Actually I still have the old round thermo that I can use as a backup if needed but for now it's mounted about half way across the basement from the stove just so I can monitor the temps. down there.

Stay away from the Milli-volt t'stat...you would want any 24 volt type.

Ok, so I emailed Honeywell about the battery in the thermostat. They said it's not replaceable, and you have to buy a new thermostat if the battery dies. Oh well, I'm looking into a digital anyway. I saw Honeywell has a digital version of the little round white analog, but if that one has the same permanent battery maybe I'll stay away from that as well.

ytseman3 wrote:They said it's not replaceable, and you have to buy a new thermostat if the battery dies.

I think you got a tech that didn't understand everything he knew. I found it hard to believe Honeywell would make a device that a dead battery was call for replacement so I phoned them & pinned them down. A senior tech told me the battery is for the initial start up only. Once the thermostat is on line and has been set up the battery can die and it not only does not effect the thermostat, it does not need replacement. If you removed the thermostat after the battery died and let it sit for a month or two the capacitors might drain and you might run into a dead thermostat, but it's a very unlikely event.

The new "round" Honeywell t-stat that replaced the old mercury model is not very good. Stay away from any "power stealing " thermostat- this would be a digital style that does not have 2 to 4 aaa or aa batteries. They don't work right and they can also damage oil and gas controls on conventional heating units.

Wow, thanks Freddie for checking into this for me.. it is still working but it is 5 years old now and I was just curious as to how long this therm might last me since I saw it had a battery. Anyhow, if and when I do replace it with a digital I will be looking for one that uses replaceable batteries like Oilman recommends.

So what is the life expectancy of the little round white themostat? Anyone have any numbers to throw out on how long theirs lasted?

I am curious what the battery is for. I just put one of these in and nothing eludes to why it needs a battery. There must be some programmable chip in it for the anticipator or something. The anticipation is set via dip switches on the back of the thing. The setpoint is still a dial and pointer.

Another case for the enviromental whacko's. Can't have mecury around because somebody let their kid eat a thermostat or we got too many slobs out there that can't properly dispose of the old ones. Got to replace old reliable technology with safe failable new technology at a considerable increase to cost to "save the environment".