How Does a Furnace Start

Your furnace starts when it receives a signal from the thermostat that tells it to turn on. … When the thermostat sends its signal to the furnace, the furnace gas valve opens and ignites the burner component beneath the combustion chamber.

What turns on first on a furnace?

Hot surface ignitor begins getting hot / direct spark ignitor begins to spark. Gas Valve opens. Furnace Lights. Flame Sensor senses flame.

How a furnace works step by step?

1. Natural gas or propane is ignited in the burner.
2. The flames heat up a metal heat exchanger and exhaust out of the flue.
3. The heat exchanger transfers its heat to the incoming air.