Installation Manual

28
DESCRIPTION OF COMPONENTS
The descriptions below are various functional components that affect the operation and shutting down of this furnace.
Some of these components and their locations are shown in Figure 23. If any component of the furnace must be
replaced, use only factory authorized replacement parts specified in the Replacement Parts List provided online.
Blower Limit Switch: Prevents operation when blower is not operational.
Flame Sensor: Verifies when a flame has carried over from the igniter to the opposite end burner. If no flame is
detected, the furnace will shut down within 4 seconds.
Flame Roll-Out Switch: Verifies that the burner flames are drawn into the heat exchanger tubes. If the burner
flames are not properly drawn into the heat exchanger, the flame roll-out switch will close the gas valve and initiate
the shutdown cycle.
Gas Valve: Controls the flow of gas to the burners. When the gas valve is energized it automatically opens and
regulates the gas pressure in the manifold.
Inducer Assembly: Vents products of combustion to the outside.
Pressure Switch: Verifies that the inducer is drawing the combustion gases through the heat exchanger. The
pressure switch prevents furnace operation with excessive flue/condensate blockage or improper inducer operation.
Main Air Limit Switch: Prevents the air temperature leaving the furnace from exceeding the maximum allowable
outlet air temperature.
Figure 23. Furnace Components
Blower Assembly
Inducer Assembly
Gas Valve
Gas Manifold &
Burner Assembly
ON/OFF Switch
Control Board
Limit Switch
Inline Drain
Assembly
Igniter
Flame Sensor
Roll-Out Switch
Combustion Air Pipe
Exhaust Vent Pipe
Main Air Limit Switch
24V Tr ansformer
Motor Choke