"Rod Dahl" wrote in message
...
I have a 4 year old Lennox gas forced air furnace. When I get up in the
morning and turn the thermostat up from say 68 degrees to 72 degrees, the
furnace fires up and heats the house up to 70 degrees and shuts off.
The
digital thermostat still displays the icon calling for heat, but the
furnace
stays off for 5 or 10 minutes and then starts up again and finishes
heating
the house to 72. After that, it maintains the temperature perfectly.
It seems the thermostat is working properly because it shows that it's
calling for heat. Why would the furnace shut off prematurely like that?
Thanks


Does the furnace fan continue to blow or does is the burner still lit in the
furnace?

There are switches that turn the fan or the burner on and off if the
temperature in the plenum is too hot or cold.