Hi,
For a Nortron electric furnace, I noticed recently that it seems like the furnace heater element is able to turn on independently of the blower fan. This seems like a safety hazard or at least a design flaw. I noticed this with an infrared thermometer as the furnace was about 20C above ambient, however the furnace fan was not on at any time.
I had heard some thermal expansion noises in the ducting on cold days, where the thermostat would trip, however I had the fan set to off expecting this would fully disable the furnace. After investigating the thermal expansion noises I noticed that the furnace was about 20C above the room temperature, however the furnace fan was not on at any time. I believe the furnace heating element is turning on when the 2 wire mercury thermostat circuit closes, and then it must overheat and a thermal trip cycles the heating element on and off.
The furnace has three easily user accessible labelled switches:
three way "fan control" switch: labelled switch positions: fan,off,on
two way "energy saver" switch: labelled switch positions: mild weather, cold weather
two way "summer switch" labelled switch positions: ventilation, heating
In the case described I have the switches set to these positions:
fan control: off energy saver: mild weather summer switch: heating
As mentioned the thermostat is a 2 wire mercury thermostat, I think I should rewire a 6 wire thermostat in that implements proper logic to control the furnace. But I'm curious if this is a design flaw or potential safety hazard (to overly rely on an internal thermal cutoff circuit)
The electric furnace is on a 240Volt 100Amp breaker.
cheers, Jamie