OT House Thermostat--Help!

I have a stuck thermostat. Its been shut down to 55 since early afternoon but the electric baseboard heaters are still cooking and the temp is 76* in the room. There's mercury in a little glass bubble that moves as it should when you turn the dial. I've tried to beat on it and blow the dust out of it but I really have no idea what to do with it. If it doesn't shut down before I go to bed I'll have to kick out the breaker in the fuse panel.

Meant to say its set at 45* and any ideas what goes wrong with these things or what to fix????

The best thing to do would be to put in a new thermostat. I would turn the breaker off at night just to be on the safe side. I just put baseboard electric heat in my house and none of the thermostats are mecury. A matter of fact all of those style thermostats were not recomended for baseboard heat.All of mine are double pole thermostats.

The thermostat you show is not the type that is supposed to be used on electric baseboard heat unless it is operating a relay system. The safest way is to use a double pole thermostat.

The common way is for the current to go through the thermostat. So it would need to carry the total amp load.

The kind you have pictures is just usually for handling the low voltage load of a furnace system. That is usually only 32 volts and very low amperage.
New double pole thermostat

It may not be the thermostat; it may be a sensor in the furnace itself. Mine was acting up just last week---it would come on but wouldn't stay on long enough to raise the room temp to the thermostat setting. My furnace guy came and finally zeroed in a metal rod, about the size of a 16p nail, with a ceramic base. He said it had developed a film. He took it out and lightly sanded it, reinstalled it and the furnace has been working fine. Sorry, I can't remember what he called that little spike.

Disregard my post. I failed to notice you were talking about an electric system. Mine is gas.

Thatlittle thermostat cant control the baseboard unit / units directly. You must have a contactor(relay) somewhere that has contacts that are closed by a signal(mercury switch closes) from the thermostat. likely the thermostat wires are shorted together or the contactor contacts are welded together.

as others have said, it is most likely a stuck relay, and if you have no idea were they are located I would suggest you call an electrician before something bad happens

Looks like someone tied a central air unit in with baseboard heat. The relay & contactors for the heat will be in the ac air handler if that's what was done. What a nightmare.

First things first, disconnect the T-stat and see if heater shuts down. If it does then its the t-stat if not then the problem is with the unit itself.

Don"t ditch that thermostat; it"s one of the BEST made. I HAD a programmable thermostat that the points "welded" on and the temp in the house was over 95 degrees when I discovered it. The ones that say there"s a relay are right on the money. That relay has done what my non-mercury thermostat did--seized.

The electric resistance baseboard heaters shut down about 15 minutes after I posted last night. This morning the room is back down to 64. I turned the thermostat back up to 70 and I can hear the panels clicking as they warm up. So I take it I had a stuck relay somewhere? If the points were welded then it wouldn't have shut off? I believe there are no heavy wires going to the thermostat so the relay that stuck must be in the panel somewhere? Is this a part easily replaced or do I need a new panel?
I'm not sure what to think because all I did was tap on the thermostat some and never touched the panels themselves where the stuck relay is supposedly located.

That thermostat is not directly connected to the heaters. Somewhere in the system there is a electromagnetic relay that is controlled by that thermostat and the relay opens and closes the circuit to the heater. The relay contacts are probably stuck together. Find a new relay.
As far as programmable thermostats go, it sounds like a nice idea but the ones I have seen , you must program MTWTF with the same times and temps.
And you can program Sat and Sun different from weekdays, but sat and sun have to be same times and temps.

that is the best thermostat ever made
you had a contactor sticking in the power circuit to the heaters.
call an electrican or a heating tech to replace the bad contactor

Just a suggestion but if I was you I would get an electrician or heating and cooling man in and have it checked out. It could do it again and you might not be home when it does it again.

Leave to old stat there but disconnect the wires and connect to a new stat that only you know where it"s located.
Possibly a stuck/welded contact . That stat probably controls a relay/contactor somewhere?

My programmable thermostat you can program each day individually (honeywell). Depends on how much money you want to spend. Also the new "Nest" thermostat looks like the old honeywell"s (round) and supposedly self programs.

Have you got a model number for that thermostat so I could try to find one.

The thermostat in the picture is a Honeywell T-87F with standard "heating only" sub base. If it were connected to central air it would have the selector switches for "cool-off-heat" along with a fan "on/auto" switch and a Q539A sub-base. Regardless, this is a 24volt control and cannot be directly connected to your 240 volt base board.

IF this thermostat in fact controls the base board heater(s) in question there will be a junction box or control box in the circuit that houses a 110v to 24v transformer for the power supply of the circuit and also a contactor(s) to energize the high voltage circuit to the baseboard heater. A contactor is nothing more than a heavy duty relay, most of the time with exposed contacts that are visible, especially in the lower amperage range required for a small wattage heater.

When you find that control box look closely at the contact surfaces of the contactor(s) with a good light and you will probably notice extreme pitting (rough surfaces) and a lot of blackened discoloration. Once they pit and become rough they can occasionally get stuck together and the springs responsible for opening them when the circuit is satified are not able to disconnect the contacts.

Usually when a 24vac low voltage thermostat is used to control baseboard, the baseboard thermostat is either bypassed (non-existant) or is turned to the warmest setting, which will be clockwise. Either of these cases, then allows the standard room t-stat to control the room temp by use of the contactors described above.

IF in fact you have a contactor stuck closed AND still have the baseboard thermostat (live voltage) installed in the baseboard, USUALLY the one on the baseboard can still be adjusted to the mid-range or lower setting to control the temperature in the room.

There are a lot of variables here to look and to help more specifically, we may need additional information as to what you found.

Good luck and keep us posted please.

Try WW Grainger and ask for information on a Honeywell T7300...it will do just about anything you'd desire, but is quite pricy.

For a much cheaper alternate, try a White Rogers 1F97 1271 which will be a very good touch screen commercial style stat for around $120 or a White Rogers 1F85-277 which will be adequate for virtually all residential HVAC and a lot cheaper at around $80.00. They may be for multistage use, but all you have to do is use the first stage of heat and the first stage of cool, all which will be explained in the booklet. There'll be a 1-800 number to call for tech support (if necessary) on the Honeywell or W/R)

Hope that helps a bit....(but I'm not totally sure W/R is available through WWG.)