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Why won't my thermostat shut my heat off?
I installed a new Honeywell CT87K thermostat, and my heat will not shut off. I have hot-water baseboard heat. There are only two wires, and I have them in the right places (at least, I am pretty sure LOL!). There are two switches, and I believe I have them set correctly (only one option referred to hot water heat, so I selected this). My furnace is 40 years old, although I do not know why that would make a difference. I have two zones in the house, and the second one is operating properly on the other thermostat. I replaced the thermostat for this zone in November, and either it worked properly for a couple of months or it was so cold out that the furnace staying on kept the house at the correct temperature. Last week, it was apparent the heat was not shutting off and I replaced the almost new thermostat with a brand new one and the heat is still not shutting off... I can't believe that I have bought two faulty ones in a row! If this sounds like an installation error, what would be something I could change that could make it operate properly? All I think I can do is reverse the two wires and mess around with the switch settings... or, is there something else? I am TOO HOT and probably spending a gazillion dollars on gas! HELP!!!
4 Answers
- ?Lv 41 decade agoFavourite answer
I would get the thermostat and use an multimeter on it.
First remove both wires from the thermostat and figure out which one is hot from the heater. You should see the DC voltage coming from the heater on the one wire (think its 12 volts). When you change the temperature on the thermostat one of the terminals should be getting hot/cold as you go from 60 degrees to 90 degrees. Make sure the return wire is connected to that terminal.
if it still does not work sounds like the 2 wires are crosses somwhere, disconnect both ends (at thermostat and furnace) and put a contunity check on the wires to see if they are crossed.
- ?Lv 45 years ago
You have a couple things going on. First, you mentioned it is "really cold". When it is really cold, heat pumps do not work very well. When the outdoor temp drops below a point between 20° and 30° (this varies by installation) the heat pump can't put out enough heat to keep the house warm. There should be a temperature switch in the condensing unit that disables the compressor and forces the heat strips (emergency heat) in the air handler to run. This switch may not have been installed on your system or it may need to be adjusted. Next, the temperature variation in the house.... Due to the marginally warm air coming from the vents, any room that is better insulated and has less draft than the other rooms will be warmer. If the temperatures are always different in these rooms you may need to adjust the air flow from the registers. With warmer air coming from the vents this difference may not be so noticeable. Place a space heater in the cold room. Close vents in unused rooms. Use blankets when you can. If you must have the whole house warm, switch the emergency heat on as needed. It's cold out there! Expect to pay more to stay warm. The emergency heat will cost much more to operate.
- jusviciousLv 41 decade ago
Doesn't sound like your t-stat. Remove the good one from the other zone and install it where the other t-stat is and see if it works correctly or not. If it doesn't then you probably have a bad or sticking hot water valve for your heater. It will be located on the baseboard or by the boiler itself. You are correct in only having 2 wires R, W. Make sure you removed any jumper wires that are connected to any other letters on the t-stat too. Hope this helps if not you can e-mail me
Source(s): HvacTech - reddog_1965Lv 51 decade ago
Sounds like you got the wrong thermostat for your furnace. You need to make sure its rated for yours. You can take the Model of your furnace with you and tell the person this is what you have or go to a Digital one that will work with all kinds. Now another thing is to make sure you level it. If not it will not be at the right temp. I also like the programmable ones but they can be fun to set up.
