My previous furnace tour video @    • 1977 (Old) Lennox Gas Furnace Overvie...  

Here is my old 1970's Lennox natural gas furnace running a full heating cycle. This is a model # G8D2-82-3. I'm not an HVAC expert, however here are the steps I see happening:
1. Standby mode, the pilot light is burning and that's it
2. Thermostat calls for heat, triggers the gas valve to open and light the main burners. The main burners heat until the thermo switch above in the heat exchanger tell it that the exchanger is up to temperature
3. Once the thermo switch is hot enough it turns on the blower fan in the bottom of the furnace box
4. Heating continues as long as the thermostat says to run
5. Thermostat says stop heating at which point the gas valve is signalled to turn off the gas but keep the blower motor running to cool down the heat exchanger
6. Once the heat exchanger has reached it's lower temperature limit the fan is turned off and the unit sits idle until called upon again.

NOTE: I have removed the front panel so you can see the components, you should not run your furnace without the cover in place during normal operation.

#Lennox #Furnace #ASMR

Chapters:
00:00 standby mode, pilot light only
00:16 thermostat calls for heat, lights gas burners
01:45 blower fan turns on, heating cycle runs
04:19 thermostat tells furnace to stop, gas valve closes
06:54 blower fan turns off, heating cycle complete