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10 Inspect the furnace venting system to make sure it is in
place, structurally sound, and without holes, corrosion,
or blockage. Vent system must be free and clear of ob
structions and must slope upward away from the fur
nace
. Check flue pipe, chimney and all connections for
tightness and to make sure there is no blockage. Vent
system should be installed per the National Fuel Gas
Code
11 Inspect the furnace return air duct connection to ensure
the duct is sealed to the furnace. Check for air leaks on
supply and return ducts and seal where necessary
.
12 Check the condition of the furnace cabinet insulation
and repair if necessary.
13 Perform a complete combustion analysis during the fur
nace inspection to ensure proper combustion and oper
ation. Consult Service Literature for proper combustion
values.
14 Verify operation of CO detectors and replace batteries
as required.
Perform a general system test. Turn on the furnace to
check operating functions such as the start-up and shut-off
operation.
1 - Check the operation of the ignition system, inspect
and clean flame sensor. Check microamps before and
after. Check controls and safety devices (gas valve,
flame sensor, temperature limits). Consult Service
Manual for proper operating range. Thermal Limits
should be checked by restricting airflow and not dis
connecting the indoor blower. For additional details,
please see Service and Application Note H049.
2 - Verify that system total static pressure and airflow set
tings are within specific operating parameters.
3 - Clock gas meter to ensure that the unit is operating at
the specified firing rate. Check the supply pressure
and the manifold pressure. On two-stage gas furnaces
check the manifold pressure on high fire and low fire. If
manifold pressure adjustment is necessary, consult
the Service Literature for unit specific information on
adjusting gas pressure. Not all gas valves are ad
justable. Verify correct temperature rise.
Repair Parts List
The following repair parts are available through Lennox dealers. When ordering parts, include the complete furnace model
number listed on the CSA International nameplate -- Example: ML180UH045P36A. All service must be done by a li
censed professional installer (or equivalent), a service agency, or the gas supplier.
Cabinet Parts
Upper access panel
Blower access panel
Top Cap
Control Panel Parts
Transformer
Integrated control
Door interlock switch
Blower Parts
Blower wheel
Motor
Motor mounting frame
Motor capacitor
Blower housing cutoff plate
WARNING
The State of California has determined that this prod
uct may contain or produce a chemical or chemicals,
in very low doses, which may cause serious illness
or death. It may also cause cancer, birth defects or
reproductive harm.
Heating Parts
Flame Sensor
Heat exchanger assembly
Gas manifold
Combustion air inducer
Gas valve
Main burner cluster
Main burner orifices
Pressure switch
Ignitor
Primary limit control
Flame rollout switches
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