How is Furnace Energy Efficiency Measured?
Schedule a professional tune-up every fall (before you first turn on your heating system). They will be able to test your heat exchanger for cracks, clean your pilot light, inspect the ventilation system, and much more.
Thermostat and Gas Valve
Your furnace starts when it receives a signal from the thermostat that tells it to turn on. Depending on the temperature you set, when the thermostat detects the air temperature dropping below that number, it activates the furnace.