Thermostat changes setting on its own! (Honeywell CT3200)

[cn]

Alright,

This one is weird, sounds like a ghost movie.....

We have a 2-story house with 2 tstats, but only 1 tstat is acting weird.

* First floor and basement:
- Controlled by tstat #1: Honeywell CT3200 (installed 2005, so 7 year-old tstat)
- Furnace is Tempstar 80% eff. installed by HVAC Co. in 2009.
- AC is Tempstar from 1991, itself running fine.

* Second floor:
- Controlled by tstat #2: Honeywell CT3200 (installed 2005, so 7 year-old tstat)
- Furnace is Tempstar 80% eff. installed by HVAC Co. in 2009.
- AC is Tempstar from 1991, itself running fine.


Tstat #2 is acting weird.
- We have been using this particular Honeywell CT3200 tstat for 7 years, so we know how to use it.
- Outside is 100F+ these days, so we set it to 82F (I used the "HOLD Temp" button, not "RUN Program" button).
- A few hours later, noticed AC running all the time. Checked tstat, its setting is now 76F.
- Wondered if wife and kids played with it, all said no they did not play with it.
- This has happened a few times.
- Tonight, went to bed, set at 82F, 2 hours later woke up because AC runs all the time, setting went down to 76F again.
- I am home alone, so now I know for sure this happens on its own!!!

So, I google "tstat changes setting on its own" but could not see anything relevant.

Anyone here has anything like this happens to you?

PS: What is a good replacement tstat similar to CT3200 (programmable 5-2) now?

[dan sw fl]

Alright,

This one is weird, sounds like a ghost movie.....

We have a 2-story house with 2 tstats, but only 1 tstat is acting weird.

Tstat #2 is acting weird.
- We have been using this particular Honeywell CT3200 tstat for 7 years, so we know how to use it.
- Outside is 100F+ these days, so we set it to 82F (I used the "HOLD Temp" button, not "RUN Program" button).
- A few hours later, noticed AC running all the time. Checked tstat, its setting is now 76F.
- Wondered if wife and kids played with it, all said no they did not play with it.
- This has happened a few times.
- Tonight, went to bed, set at 82F, 2 hours later woke up because AC runs all the time, setting went down to 76F again.
- I am home alone, so now I know for sure this happens on its own!!!

So, I google "tstat changes setting on its own" but could not see anything relevant.

Anyone here has anything like this happens to you?

PS: What is a good replacement tstat similar to CT3200 (programmable 5-2) now?

Is the Battery LOW ?
or Replace with similar.*

http://www.lowes.com/Thermostats/Pro...tats_Pop_Cat-2

_ The Ghost is obviously Hot as Hell.
or it may be re-setting to the Factory default

_ I was Not able to verify which one of these t-stats actually has a GHOST Warranty.
_ WellHoney just contact the mfg

[mark beiser]

I used the "HOLD Temp" button, not "RUN Program" button

When you do this, does the word "HOLD" appear in place of the time on the LCD display?

[jtrammel]

Batteries

[cn]

Batteries

- Removed batteries, they are 1.37 Volts, is that low?
- Also the "Lo Battery" indicator never showed up on the display.
- I will replace the batteries to see if the symptoms return or not.

- Interestingly, even with batteries removed, the tstat LCD display still works, does that mean power supply come from the furnace transformer?

--------
mark beiser...When I press the HOLD button, the word HLD appears as usual. Nothing out of the ordinary.


PS: I am thinking about Honeywell RTH2300B just in case...

[jtrammel]

Yes you can hardwire the tstat, use batteries, or both. Most times when tstat acts funny it's due to old batteries that corrode and leak acid into the circuitry of the tstat

[cn]

Yes you can hardwire the tstat, use batteries, or both. Most times when tstat acts funny it's due to old batteries that corrode and leak acid into the circuitry of the tstat

Installed new batteries (I checked them before install, they were 1.60V, brand new).

Same issue happens...Set it at 84F, a few hours later it mysteriously changed setting to 76F.

I think I have a rare issue (maybe 1 in a million kind of thing). Something goofy inside the tstat just messed up.

PS: Looks like I will replace my existing tstat with Honeywell RTH2300B.

Thank you all for your advices.

[small change]

We had this problem once

Customer had issue with the very same thermostat/problem

granted this was probably 20 years or so ago.

Our customer's house was right next to a major freeway in Cleveland Ohio.

The factory rep and their engineers speculated that the overpowered CB Radios from the Truck driving on the interstate were causing confusion with the digital thermostat.

Also if you are near a airport or an interstate.... someplace that gets that type of radio traffic

That may be the answer.

Course we went to a mechanical clock thermostat back then and really didn't have an issue
or really had any further opportunity to test Honeywell's theory regarding this issue

[cn]

Problem solved....read on...

- So got new Honeywell RTH2300B, which has a smaller "footprint" (smaller size) than the existing thermostat CT3200 series.
- The smaller size of the new thermostat creates a new problem of paint matching.....now I have to patch the holes in the wall with drywall mud, sand it smooth and paint the wall to match existing color, what a pain!

- Put in new Honeywell RTH2300B, fresh new batteries.
- Guess what, roughly at 10PM, the tstat reset itself to 76F. Now I got mad.
Why always 76F but not 74F or 72F or 70F?
I was about to call a priest to chase this Ghost....

- Next morning, google about "thermostat reset itself" and find something about ground wires near the furnace that can get damaged and cause all kinds of problems. I was about to go to the basement and investigate the furnace area to see if any wires get loose.

- During breakfast, I was sitting next to my 11-year-old son and happened to ask him "did you mess around with the thermostat?".

My son: "I don't know what a thermostat is, but is that the 'thermometer' thingy that you adjust all the time?".
(obviously he does not the difference between thermostat and thermometer)...
Me: "Yes".
My son: "Oh, it was a bit hot last night so I adjusted it down to 76F".
Me: "why 76F but not 70F?"
My son: " I love math and I like number that ends in even number, and I happen to like number 6".
Me: "So you have been doing this adjustment all along?".
My son gave me a cute smile....

So guys, this is a happy ending...

Thank you all for your advices, I feel guilty for asking you guys a question that could have been solved by more persistent questioning of family members!

PS: Lesson learned...when talking to kids, don't use fancy word like "thermostat", better yet, bring them to the very device (in this case the thermostat) and ask them about it.

[Sleuth]

.


..

[jtrammel]

Priceless

[ar_hvac_man]

-
- Interestingly, even with batteries removed, the tstat LCD display still works, does that mean power supply come from the furnace transformer?

Most digitals will have a battery or capacitor that will keep keep the stat energized so you dont lose programming, set points, etc, while changing batteries, servicing, power outages

[Rodney28334]

Glad it worked out. I Cant blame him, at 82 I would be ghosting that tstat down too.