I recently replaced my thermostat and upgraded from a mercury based
thermostat to an electric programmable model and am having some issues
with my furnace. Let me know what you think:
When I turn the furnace blower on "auto" and the heat to on and set a temp
above the room temperature, the heat turns on, the fan turns on, and the
house is brought up to temp. The furnace kicks off and the fan keeps
running. When I turn the thermostat to "off" from "heat", the fan still
runs. The only way to get the fan off (ironically) is to turn the fan
setting to "on" from "Auto" and the system shuts down.
When I installed the new thermostat, I don't think I diagrammed the old
wires (stupid, I know) but could incorrect wiring be causing this problem?
If not, do you think this is a fan/limit control issue? This is an older
furnace (an Imperial II from GE, at least 15 years old MODEL NUMBER
21LU130K28) and the thermostat is a honeywell RTH111/221.
Any advice here would be appreciated.