Tweet
I have central heating/air conditioning with a mercury thermostat. When I turn on the air, it turns on and off as it should relative to the temperature setting. When I turn on the heat, it fails to shut off even when I flip the switch to off, I have to turn the switch to AC then to off for the system to stop. I've turn the breaker off for about half an hour then turned it back on in hopes of resetting the system but the heat isn't shutting off once the temperature is reached.
-
-
the old round honeywell thermostat has a heat anticipator under the brass plastic cover. look for a copper colored pointer and a scale of numbers. match the pointer to the burner current rating or if it is gas, the gas valve current. usually printed on the valve. this will lessen the burner short cycling. -
It's not that old of a thermostat. It's GE and is rectangular shaped. The temperature setting on top with the reading on the right, and further to the right is the Heat/Off/Air, etc. Under the cover are two bars with mercury in them, one positioned atop the other.Comment
-
the mercury bulbs are just switches that have to be mechanically operated by some means - a bi-metallic coil for temperature, a taut plastic membrane and a linkage for humidity. electronic thermostats use a solid state switch called a triac. a magnetic reed switch is mechanical and can be actuated by a common magnet or a coil of wire wrapped around the switch. the reeds are vacuum sealed in a glass bullet.Comment
-
Central Heating not turning off
We need to see if the problem is in the furnace or thermostat. Turn the heat on, go to your furnace and disconnect the white coming from the thermostat.Originally posted by Almost Able View Post
If the heat stops then the problem is not in the furnace. Try this first.
Why are you using a two stage thermostat?
What color wires are on the stat and what post do they hook to? and what do they hook to in the furnace? PaulComment
Comment