we have a three zone baseboard hotwater furnace. a few months ago one zone would randomly stay on, we did change the thermostat we have not noticed the problem again, but in another zone we have the same problem, we changed the thermostat & it has not helped, the heat stays on no matter what temp we set it on, we have to shut the furnace off. please help.
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1You could have a mis-wired thermostat, or a bad zone valve. Have you tried it with the thermostat disconnected?– TomGCommented Jan 2, 2012 at 20:39
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yes, we took the thermostat off the wall & the heat was still on.– candyCommented Jan 3, 2012 at 23:05
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3 Answers
Try to replace the valve motor first. It is much cheaper and easier, and many times it's the motor that has gone bad, not the entire valve. To test, set the zone valve to auto (which is what is likely is in) and note if it won't turn on. Then turn it to manual open. If it turns on, your motor is likely bad.
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I had this issue and the valve motor was the problem. Unfortunately I hadn't seen your advice first! The HVAC guy knew the problem before he ever looked at the boiler. An expensive lesson!– MgSamCommented Apr 29, 2021 at 15:57
If you actually removed the thermostat from the wall, but the heat stayed on, more than likely the R wire is connected to the W wire somewhere in your system. Go to the furnace itself, and look at what is connected to the terminals on it. Try undoing terminals (one at a time!) until it stops, then continue troubleshooting from there.
That's not the problem. The zone valve is not working. Zone valves stick either in the open or closed positions when they go bad. In your case bc heat won't go off its stuck in the open position. Need to replace zone valve
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1That's assuming you have a valve system rather than a circulator-pump system.– keshlamCommented Dec 17, 2014 at 15:41