Question about Honeywell Electronic Programmable Heat/Cool Thermostat - CT3300A100 Heater

4 Answers

Electrical burning smell in house

We recently (about 4 months ago we had a digital thermometer installed to replace the old one. Twice this week there has been an 'electrical burning' smell when you go into the living room (where new thermostat is located). At first we thought is was a new cordless phone so we unplugged that and the nightlight in that outlet and it seemed to have gone away. Tonight it is back. It appears that it is near the thermostat (opening in the wall where it is connected).

The walls are not warm, there is no smoke and we've checked from the basement and didn't see anything. (not certain of the brand below but i know it works for both heat/cold)

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  • mhenn Feb 05, 2009

    We have gas heating (with radiators throughout the house). We do not have electrical heat strips. The furnace is located in the basement which is one floor below where we are smelling the smell. (note: the furnace is not directly below the smell). There is no smell anywhere else in the house and the heating system is still working.

  • mhenn Feb 05, 2009

    Sorry for the confusion (I'm new at this). It is a boiler. And this is not the first time that the boiler/heat have been used this season.

  • mhenn Feb 05, 2009

    No fires in the house. We've lived there almost 25 years. The house is probably 80 - 90 years old.

    Our neighbor (a plumbing/heating retiree) came over and looked today to make sure that the old line that was connected to the previous clock on the old thermostat (remember we replaced the old one about 4 months ago) was in fact disconnected (it was). We have not had the burning smell since last night.

  • mhenn Feb 06, 2009

    Yes, there is a fireplace in the same room but it has not been used in at least 8 years.

  • mhenn Feb 07, 2009

    Problem SOLVED! Thanks for all of your help. It turned out to be old/frayed wiring in a plug that was behind the couch (on the same wall as the thermostat). We, unfortunately, found out the hard way as there was a small fire behind the plug in the wall, BUT thankfully it was very small, and immediately put out b/c we were on top of it and were still investigating the problem.

    P.S. We have since had the fire dept. and an electrician to fix things so all is well. Thanks again for troubleshooting.

  • Mark Egan May 11, 2010

    Is there a fireplace in the house, and if so, how near to where this room is?

  • Mark Egan May 11, 2010

    Has there ever been a fire in the house that you now of?

    If so, how long ago?

    Did you live in the house when the fire occurred?

    How long have you lived in the house, and how old is the house?

  • Mark Egan May 11, 2010

    Does the "furnace" heat water for the radiators? Or is the furnace a secondary heat source for the space that is forced air?

    Is this the first time this season the forced air heat has run?

  • Mark Egan May 11, 2010

    If the heating system is still working, then I would be looking at the heating system. If the problem was in the thermostat, then it would have failed and the heating system would no longer be looking. Heaters themselves cause more fires than thermostats.

    You don't say what kind of heating system this is (gas, LP, or oil), nor where it's located with respect to the space where you smell the burning (or any other unit that may be nearby, but does not serve that area). Are they in the basement, in a closet, or in the attic.

    Replay back and I will try to help more.

  • Mark Egan May 11, 2010

    Glad you got identified it before serious damage occurred. Sometimes it's hard to see the bigger picture, and smelling the smells, through these teeny tiny wires.

  • Mark Egan May 11, 2010

    Downdrafts in fireplaces, and odors, are very hard to track. Even though the fireplace has not been used in 8 years, you can still get odor from it, with the right temperature/humidity conditions.

    I don't want to lead you away from investigation of the source, but my inclination is to say you probably don't have a fire condition, since it's been at least 30 hours since you originally posted. If you had a smoldering fire, it would have either turned into a full fledged fire by now, or it's has gone out on it's own. I think the stat replacement was just coincidental, and/or, your sensitivity to the odor was much higher when you smelled it (kind of the cigarette smoke issue. Some can handle it, others can't. And the degree to which some can handle it, and others can't, are hard to measure.

    Reply back if you have any further question or comment. I hate that there was not a specific solution, but, it's hard to identify the specific problem in cases like this.


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Wednesday night we could smell something burning in my back bedroom we had to call the fire dept to my house they were there for 2 or 3 hours turning to find out what the burning smell was coming from they couldn't find out what it is we had somebody to come and look at the plug in but there has been nothing plug in there we had to shut the power off in that room and it still smell like something is still burning in there what is going on?

Posted on Jan 17, 2010

  • k ayers
    k ayers Dec 11, 2014

    I would think it's something electronic from your description of selling something burning.


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Mhenn, It is my guess that the 'electrical burning' smell is from your heating system. Since there is no smoke and the walls are not warm.... then there is no real problem. The smell maybe just dust has collected in the duct work that is burning off the central heating systems electrical heat strips. If you have electrical heat strips then that may be the problem. If you have a central gas heat system, it may be the same type problem. Hope this helps you. Henry

Posted on Feb 05, 2009

  • Debbie Missroon Jan 08, 2013

    I have a similiar situation. Woke up to an electrical smell in bedroom and great room, it was quite strong but no smoke. I checked all the plugs for working lamps and everthing seemed ok. As the day progressed and got warmer the smell dissipated. Could it have been my heater?The smell is completely gone now.


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I've seen tstats catch fire they may smell mild at first sort of like a server room where tons of electronics are running. Normally all the resistors and caps start melting away sometimes you can see it other times you can't. The reason typically is a short to ground somewhere in the wiring. It's nothing to take lightly the furnace should only smell maybe the first two times it's fired electric or heat. I think your family's safety is well worth the costs of paying a qualified hvac pro to check things over.

Posted on Nov 22, 2014

The smell may be coming from the heater, or the area where yours is located. It is possible that your HVAC system is carrying the smell to other places in your home. That being said, I would suggest getting an electrician out to check everything and make sure it isn't electrical. Good luck and stay safe! The smell may be coming from the heater, or the area where yours is located. It is possible that your HVAC system is carrying the smell to other places in your home. That being said, I would suggest getting an electrician out to check everything and make sure it isn't electrical. Good luck and stay safe!

Posted on Sep 20, 2014

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