Electric heat thermostat won't shut off

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Old 12-30-04, 04:09 AM
ScallopShell
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Electric heat thermostat won't shut off

I have electric heat in my home. Each room has it's own thermostat. Most of them have been fine, but I have replaced a certain one at least 5 times. It works fine for a while, then it just stays on and never shuts off. I have to shut off the circuit breaker to get it to turn off.
I also have one in my upstairs bedroom that all of a sudden stopped working altogether. Any ideas on how to fix it?
 
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Old 12-30-04, 08:13 AM
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Originally Posted by ScallopShell
I have electric heat in my home. Each room has it's own thermostat. Most of them have been fine, but I have replaced a certain one at least 5 times. It works fine for a while, then it just stays on and never shuts off. I have to shut off the circuit breaker to get it to turn off.
I also have one in my upstairs bedroom that all of a sudden stopped working altogether. Any ideas on how to fix it?
Are they baseboard heaters or forced air heaters? Fed with 120 volts or 240 volts?

These suggestions are based on 240 volt supplied heaters.

Thermostat nevers turns off - You'' ll need to take voltage readings at the heater. With the thermostat 'on,' 240 volts should be present across the 2 wires feeding the heater. Turn the thermostat to 'off' ( or it's lowest setting) and you should be reading 0 volts if the thermostat is a two-pole type (both power leads are connected to the stat). Or 120 volts if the thermostat is a single-pole type (one power lead connected to the stat).

Heater suddenly stopped heating - repeat the above process. If the operating voltage is present at the heater, then the heater is broke.
 
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Old 12-30-04, 09:45 AM
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My guess would be that the one you've replaced multiple times is running a higher load than the others. Bigger room with more baseboards? Sounds like the contacts are welding together over time. You could switch to a relay type of thermostat or look for a higher capacity line voltage thermostat. Find out how many watts the thermostat you have is and replace with one rated for more. To truly do this correctly, add up the wattage of all the baseboards the thermostat controls and get a new thermostat that is rated above the total.

As for the room that is no longer working, follow thinman's directions.

Doug M.
 
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Old 12-30-04, 10:02 AM
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I'm going to move this thread to one of the HVAC forums. In my experience, those guys know more about thermostats than electrician types.
 
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Old 12-30-04, 10:13 AM
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I'm assuming we're talking about line voltage thermostats

not low vlotage.
 
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Old 12-31-04, 06:51 AM
ScallopShell
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OK here's what I know about the system

1) Each thermostat has 2 wires connected to it. They are small wires (18 or 20 guage).
2) The heaters have 1 feed into them, so I assume it's 110 vac.
3) My guess of how the system works. Thermostat connects to a relay at the heater which has low voltage control and makes the 110 vac circuit. I suspect the problem is that the thermostat control and the relay need to be purchased in a pair. ?????????????
 
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Old 12-31-04, 10:02 AM
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Wow. I'm way off on this one. I wouldn't think the relay would have to be replaced with the thermostat, but there may be some adjustments on the thermostat that need to be made when installing it and after 5, it's probably smart to replace the whole set up and start new.

Doug M.
 
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