Home Thermostat

[IT Guy]

Hi,

I have a Honeywell Chronotherm IV model T8600 thermostat in my house that is starting to give me problems. It is the master for a 3 zone system. The other two are a smaller model and have no issues.

For the last couple of weeks it has been resetting itself to 1:00 pm , the time doesn't move from there and the display keeps blinking. When it does this it ignores the "sleep" and "wake" settings but kicks the heat on at the normal "wake" setting. This happens about every other day now.

Now it has also started a new trick in addition to the first. The display goes completely blank, no buttons work and the heat comes on and never shuts off. The only way to make it stop is to disconnect the thermostat completely from the wall base, plug it back in and reprogram. It has done this twice in the last week.

I see no loose wires at the thermostat or the control panel in the basement or anything else - it is hardwired so no batteries.

Any ideas before I drop $100+ on a new thermostat?

Thanks

[Jim Almquist]

You said you have 3 zones so is one of the other zones the same type of thermostat so you could do a swap just to insure that the problem is not related to a power supply or wiring ?

[IT Guy]

Nope - This is the master thermostat that is having the issues. The other 2 are different, not programable and will not fit the wall plate connections.

[JohnMickish]

How is this thermostat powered? Battery or does it use 24V?

[pikechaser]

Dont do much residential work anymore..but as I recall the older 8600's...big square ones..did have batteries..and the newer ones t8600D's did not...should say low battery if it has them and they are weak...I have a feeling if it had them you would know as you would see them when you take it off the wall. Does sound like stat is junk..if you have a volt meter it wouldnt hurt to check for 24v to terminal strip on thermostat subbase for giggles. "R" terminal is power coming in...may have RH & RC terminals..probly jumped together..checking anywhere there would be ok..

[JohnMickish]

That is where I was headed with that. Sounds to me like it either loses power at times and loses memory. If it is the 24V style, I would check the terminations at both the stat and the transformer. It's possible that the transformer might be bad but I'd be willing to put more money on a bad termination or broken wire.

[IT Guy]

I will give that a shot - thanks.

[furnace man]

Replace the thermostat I am to assume it is a set back. The stat is starting to fail if you wait to much longer you will come home to a cold house. You can check the 24 v but unless it fails at the time of when you are checking it you will not know if it is failing.

[propster]

My first thought was low battery but this is hardwired. My question is "to what"? What is the power source for this type of thermostat, or are we talking a plug in to the wall?

[propster]

Never mind, if i had only read your original post more thoroughly I would have seen that indeed you plug it in. Good luck with your fix - programmable heat is awfully nice to have.