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650.75-N4U
vided. When reinstalling the filter(s) be sure it completely
covers the plenum opening.
To reinstall the filters, simply reverse this procedure.
Horizontal Applications
In most horizontal applications the filter is located in the
return air duct near the furnace or in a filter grille.
When replacing filters, DO NOT use a type with
excessively high pressure drop. Some high effi-
ciency filters available will cause the furnace to
operate improperly and could result in a safety
hazard.
Lubrication
Blower motors in these furnaces are permanently lubricated
and do not require periodic oiling.
Blower Care
Even with good filters properly in place, blower wheels and
motors will become dust laden after long months of opera-
tion. The entire blower assembly should be inspected annu-
ally. If the motor and wheel are heavily coated with dust, they
can be brushed and cleaned with a vacuum cleaner.
The procedure for removing the direct drive blower assembly
for cleaning is as follows:
1.
Disconnect the electrical supply to the furnace and
remove remove the access doors.
2.
On downflow/horizontal models only, remove the two
wires leading to the auxiliary limit mounted on the side
opposite the blower motor.
3.
On downflow/horizontal models only, remove four top
panel screws and lift the top panel enough to disengage
and remove the flue chase assembly.
4.
Remove blower assembly mounting screws and slide the
blower assembly out of the slots in the deck. If the two
shipping screws were not previously removed, also
remove and discard these two screws located on each
front corner of the blower assembly.
5.
On downflow models only, note the wire/terminal location
and then remove the blower wiring from the furnace con-
trol. Remove the protective boot and disconnect run
capacitor wires. Remove the screws securing the electri-
cal panel to the blower housing. Pull blower assembly
out of the unit. When cleaning or servicing the blower
assembly, DO NOT remove or change the balance clips
on the blower wheel.
36
6.
To reassemble, reverse the procedure, restore power to
the furnace and verify operation.
Burner Removal/Cleaning
The main burners should be checked periodically for dirt
accumulation.
If cleaning is required, follow this procedure:
1.
Turn off the electrical power to the unit.
2.
Turn off the gas supply at the external manual shutoff
valve and loosen the ground union joint.
3.
Remove the upper access panel and remove the burner
box cover.
4.
Remove the screws that hold the burner box assembly to
the vest panel and remove the assembly.
5.
Remove burners from the burner assembly.
6.
Burners may be cleaned by rinsing in hot water.
7.
Reassemble the burners in the reverse order.
Cleaning the Heat Exchanger
1.
Turn off the main manual gas valve external to the fur-
nace.
2.
Turn off electrical power to the furnace.
3.
Remove the upper access panel and remove the burner
box cover.
4.
Disconnect wires from flame sensor, rollout switch and
HSI igniter. Remove igniter carefully, as it is easily bro-
ken.
Label all wires prior to disconnection when servic-
ing controls. Wiring errors can cause improper and
dangerous operation. Verify proper operation after
servicing.
5.
Remove the screws that hold the burner box assembly to
the vestibule panel and remove the assembly. The upper
portion of the heat exchanger will now be exposed.
6.
Remove the upper cover plate at the top of the furnace.
Remove the internal baffle.
7.
The upper portion of the heat exchanger is now
exposed.
8.
With a long flexible wire brush, clean inside each tube at
both the top and bottom. The brush must pass around
the rear heat exchanger tubes. Vacuum loose scale and
dirt from each tube.
035-14370-000
Unitary Products Group
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