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WARNING:
Holes in the vent pipe or heat exchanger can
cause combustion products to enter the home.
Replace the vent pipe or heat exchanger if leaks
are found. Failure to prevent the circulation
of combustion products into the living space
can create potentially hazardous conditions
including carbon monoxide poisoning that
could result in personal injury or death.
Vent System
Check the vent pipe and/or chimney to ensure that it is not
corroded or blocked by debris. Any corroded section of vent
pipe must be replaced, and any obstruction or blockage
must be removed prior to operating the furnace.
DESCRIPTION OF COMPONENTS
The descriptions below are various functional components
that affect the operation and shutting down of the furnace.
Some of these components and their locations are shown
in Figure 18 (page 27). Refer to the Operating Sequence
section (page 17) for additional component information.
If any component of the furnace must be replaced, use
only factory authorized replacement parts specifi ed in the
Replacement Parts List provided online.
Blower Limit Switch
Blower switches prevent operation when blower is not
operational.
Flame Sensor
The fl ame sensor verifi es when a fl ame has carried over
from the igniter to the opposite end burner. If no fl ame is
detected, the furnace will shut down within 4 seconds.
Flame Roll-Out Switch
The fl ame roll-out switch verifi es that the burner fl ames
are drawn into the heat exchanger tubes. If the burner
fl ames are not properly drawn into the heat exchanger, the
fl ame roll-out switch will close the gas valve and initiate
the shutdown cycle.
Gas Valve
The gas valve controls the fl ow of gas to the burners.
When the gas valve is energized it automatically opens
and regulates the gas pressure in the manifold.
Inducer Assembly
The inducer assembly vents products of combustion to
the outside.
Pressure Switch
The pressure switch verifi es that the inducer is drawing
the combustion gases through the heat exchanger. If
the fl ame is not properly drawn into the heat exchanger
tube, the rollout switch or the fl ame sensor will shut the
furnace down.
Supply Air Limit Switch
The supply air limit switch prevents the air temperature
leaving the furnace from exceeding the maximum
allowable outlet air temperature.
19
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