Furnace Components
This component moves aire through the duct system.
Blower Motor
This switch shuts the furnace down if the furnace overheats.
Limit switch
This component is the first to start during the heating cycle in most modern furnaces.
Inducer motor
Is propane in a tank a liquid or a gas?
Liquid
This type of gas is the most commonly used one to fuel residential gas furnaces.
Natural gas
This device ignites the gas in most modern furnaces using electricity.
Hot surface igniter
This device confirms that the burners are lit.
Flame sensor
After the pressure switch closes, this component begins heating to ignite gas.
Igniter
What should the incoming pressure of natural gas be?
10-13 inwc
This pipe carries combustion gases out of the furnace.
Flue pipe
This safety device proves that the inducer motor is creating proper draft.
Pressure switch
This switch prevents the furnace from running if the blower door is removed.
A door safety switch
This is the next event after the gas valve opens.
Burner ignition
What should the incoming pressure of (LPG) liquid propane gas be?
11-14 inwc
This furnace type pulls combustion air from inside the building.
An 80% furnace
This component opens and closes to allow gas to flow to the burners.
Gas valve
This safety device shuts the furnace down if venting becomes blocked.
Rollout switch OR Pressure switch
This motor starts after the heat exchanger warms up.
Blower motor
What should be the correct manifold pressures for natural gas and liquid propane be?
Natural gas = 3.5 inwc
Liquid propane = 11 inwc
This furnace type uses PVC pipe for venting.
A 90% (high-efficiency) furnace
This furnace component transfers heat from combustion gases to the air.
Heat exchanger
This device detects improper draft in the flue system.
Pressure switch
This occurs after the thermostat is satisfied.
The burners shut off and the blower runs through the cool-down cycle.
What is the most important thing that should be checked when measuring gas pressures? (Hint: it is the last thing that you do)
Check for leaks
This dangerous gas can form if combustion is incomplete.
Carbon monoxide