26
16. Attach a round wire brush to a length of high grade
stainless steel cable. Attach the other end of the
cable to a variable speed reversible drill. Slowly insert
and rotate the cable into the top portion of the heat
exchanger. Operate the drill alternating between
forward and reverse, working the cable in and out
several times to obtain suffi cient cleaning. Repeat
this sequence for each heat exchanger tube.
17. Remove all loosened debris from the heat exchanger
tubes using a vacuum cleaner.
18. Using a bright light, check the condition of the upper
and lower sections of the heat exchanger tubes.
19. Inspect the burners for accumulated dust or debris.
If burners must be cleaned, see Cleaning of Burners
20. Replace all the parts in reverse order that they were
removed.
21. Check gaskets for damage. Replace if needed.
22. Follow the lighting instructions found on the furnace
door to return the furnace to operation. Verify proper
operation after servicing.
Heat Exchanger & Burner Maintenance
The furnace should operate for many years without soot
buildup in the fl ue passageways, however, the fl ue, vent
system, and the burners should be inspected and cleaned
(if required) by a qualifi ed service technician annually to
ensure continued safe operation. Pay attention to any
deterioration from corrosion or other sources.
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.
Lubrication
The bearings in the blower motor and inducer blower used
in these furnaces are pre-lubricated and sealed by the
manufacturer. No further oiling of the bearings is required
for the life of the motor.
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 this furnace.
Some of these components and their locations are shown in
Figure 28 (page 41). 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:
Prevents operation when blower
is not operational.
Flame 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:
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:
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:
Vents products of combustion to
the outside.
Pressure Switch:
Verifi es that the inducer is drawing
the combustion gases through the heat exchanger. The
pressure switch prevents furnace operation with excessive
fl ue blockage or improper inducer operation.
Supply Air Limit Switch:
Prevents the air temperature
leaving the furnace from exceeding the maximum allowable
outlet air temperature.
