Installed a Lux brand programmable (not “smart”) thermostat last year. Worked fine until I got home today and attempted to adjust the temperature. It refused to turn on the heat, so I checked the batteries and tried to reset it a couple of times. Then I checked the relevant circuit breaker and found it had tripped. Upon resetting it I heard a whump. Went back to the living room and found the unit charred black.
No further fire, so I made sure the breaker was off again and pulled it out of the wall. The wires don’t seem to have been damaged, but what should I do before replacing it with a new thermostat of some kind?
Also, what are some other decent programmable - but not “smart” - thermostats I could purchase?
OK, I still need more information.
Generally, thermostats are run off of 24v, from a transformer in the HVAC. The only ones that are controlling 120V that I know of are old radiant heating systems. Is this what you have? What is the make and model of the thermostat.
This is electric baseboard heating, not an HVAC system. I have a condo, and one of the regular household breakers controls the electricity going to the thermostat in the living room which in turn controls three baseboards (all in the same room). Two other rooms have their own thermostats and baseboards and were not affected.
The thermostat was a Lux ELV4. Looking it up, I found several bad reviews including photos of scorched walls very much like mine. I’ve sent a message to the company, for all the good that will do.
It would be interesting to take it apart and see what failed.
Generally, a breaker won’t trip instantly unless there is a dead short. I would guess that either a wire came loose, or a screw fell across the supply terminals.
But remember—the OP said this thermostat controlled a baseboard heater. Aren’t those often controlled by line-voltage thermostats? A short at line voltage would account for everything the OP described, wouldn’t it?
I hadn’t encountered line-voltage thermostats until I moved from WI to the Pacific Northwest a few years ago. I love many things about my new home, but mine-voltage thermostats are not among them.
I have a Lux thermostat controlling a pair of 240v baseboard heaters. It is not programmable but is certainly a line voltage unit. I can see incorrect voltage frying this unit, but given the proper voltage is 240v it seems unlikely.
I just wired up my old thermostat, the kind with a dial that would look at home in the 1950s. Reset the breaker, turned it on and it works. So I have heat again, but this is a temporary fix. Still not sure what caused the problem.
If it’s running on mains voltage, then there’s not really anything to odd about it. By that I mean, I don’t know why it happened to this specific device, but anything running on 120 or 240, right from the breaker has the ability to blow the breaker and/or heat up enough to scorch walls or start on fire.
A simple short, some arcing or a welded contact and all kinds of odd things can happen.
Just as an example if a light switch stopped working and you pulled it apart to find the guts have melted or scorched, it’s certainly not a good thing, but it’s not out of the ordinary for it to happen.
OP, it wouldn’t hurt to check the connections at the heater as well. A bad/loose connection there could cause it to pull more amps at the t-stat. The extra amps can cause plastic components to melt which results in things touching that shouldn’t be touching.