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.
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.