no call for heat, but furnace stays on

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Old 01-23-04, 04:22 PM
mikescott
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no call for heat, but furnace stays on

I can hear my digital thermostat click, but my furnace does not shut off. It is heat, not just the blower. I have to turn the heat off to shut the furnace off. The temp reads 80, the setting is 70, and the heat stays on. I'm assuming something is wrong at the furnace??
 
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Old 01-23-04, 05:02 PM
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With the info you have provided, all I can tell you is that the Red and White wires are the thermostat wires that need to be connected together to start the heat. I would suggest removing the thermostat from the wall and double checking that the wires are not touching. If they aren't, maybe you should find them down at the furnace and disconnect the white one and see if it shuts off. If it does, the problem is in the wiring coming to the furnace. If it does not shut off, the problem is in the furnace somewhere. The thermostat wires are small wires and only carry 24 volts and will not harm you.
 
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Old 01-24-04, 10:45 AM
wayww
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Is this digital thermostat new? If so, did the problem exist before it was installed? Is this a heating / cooling system or just heat? Has the system been worked on at all prior to this problem?
 
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Old 01-25-04, 06:12 AM
mikescott
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It is not a new thermostat, although I did try a new one and I still have a problem. I haven't had any work done on the furnace. It is a oil burning furnace and cooling unit as well. The thing I don't understand is what is the difference between me turning the heat completely off, or the heat on with the present temp above the setting onn the thermostat.
Either way, isn't the furnace receiving the same signal from the thermostat? What explains me being able to shut the furnace off by shutting the heat completely off, but the furnace does not shut off when the thrmostat stops calling for heat
Thanks

Mike
 
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Old 01-25-04, 07:44 AM
wayww
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First of all, all digital thermostats are not created equal. That said, here is what you need to do. First double check that your wiring is correct. The R or red wire which is 24 volt + should go to the R on the thermostat, the G or fan to G, the W or heat to W and the Y or cooling to Y. If all this is correct then you need to shut off the power, remove all the wires from the thermostat, ( mark them in case they are not color coded correctly) and do the following. Put the R&G together and restore power, you should get fan only operation. Next try R&W, this should give you heat. If this works, you have a digital incompatability. Nice word huh? If not, then you need to try the same procedure at the furnace, if this does it, you have a shorted cable.

One thing you have not mentioned. Do you have seperate 24 volt power supplies for heating and cooling? This is not uncommon especially with add on cooling systems. If you do, this could be the root of your problem. You are likely cross feeding between the two transformers.
 
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Old 01-25-04, 07:47 AM
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Tstat

Did you try like ken said just pull the R -red wire off the tstat does the burner stop then? If not pull the R red wire off on the stack or burner control box Or off the transformer . What happens then
ED
 
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Old 01-25-04, 08:36 AM
KSteele
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heat staying on

I have a similar problem except the heat does nto turn off even when I turn the system off on the thermostat. I even disconnected the thermostat and the heat seemed to stay on (I have baseboard water heat and the units stayed hot with hot air flowing out) I have two zones fo rmy heater and all seems to be fine with the other zone. Any ideas? Thanks
 
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Old 01-25-04, 08:56 AM
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Look and see how the boiler is wired. You can have the tstats turn the pump or zones on and the boiler turn on and off with a aquastat that is on the boiler so check it out ED
 
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Old 01-25-04, 09:31 AM
KSteele
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Unhappy heater that won't shut off

Based on the diagram I have, I cannot find the aquastat on my boiler. What I can find is an on/off light switch closely connected to the box with the main red and white wires, which then feeds to the two zone boxes, which have a series of red and black coated wires and a water valve shutoff. I of course also have the water and pressure gauge. I live in a remote are and no one can come until tomorrow. Can I shut off the main power switch to the boiler for a few hours at a time to regulate the heat? Any other fix I can do in the meantime before a professional can look at this?
Thanks
 
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Old 01-25-04, 10:16 AM
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Id say yes turn it off or as long as the boiler temp dont go over say 200o. Keep an eye on it all the time most of the time the boilers work from a 160o on and 180o off. So go for it till the tech can get there tomorrow. ED
 
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Old 01-25-04, 01:41 PM
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Ok oil, now were talking. The best way to check it out would be to find the safety control. It is the one with the red reset button it. It will have 2 small wires on it going to terminals marked T and T. Remove either one and the burner should stop. If it does not, the safety control is bad and should be replaced immediately. I have only ever seen that twice so it would be most unusual. More likely there is a short in the thermostat wires and the red and white are shorted.
 
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