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b. Remove screws holding cutoff plate and remove cutoff
plate from housing.
c. Lift blower wheel from housing through opening.
14. Clean blower wheel and motor using a vacuum cleaner with
soft brush attachment. Do not remove or disturb balance
weights (clips) on blower wheel blades. The blower wheel
should not be dropped or bent as balance will be affected.
15. Reinstall blower wheel by reversing steps 13 a. through c.
Be sure wheel is positioned for proper rotation.
16. Reassemble motor and blower by reversing steps 5 through
11. If motor has ground wire, be sure it is connected as
before.
CAUTION: Be sure the motor is properly positioned in
the blower housing. The motor oil ports must be at a
minimum of 45° above the horizontal centerline of the
motor after the blower assembly has been reinstalled in
the furnace.
17. Reinstall blower assembly in furnace. Connect electrical
leads to blower speed selector. Please note that connections
are polarized for assembly. DO NOT FORCE.
18. Reinstall control box.
19. Reconnect wires to auxiliary limit switch on blower housing
(downflow furnaces only).
20. Reinstall vent pipe and enclosure (downflow furnaces
only).
21. Turn on electrical power and check for proper rotation and
speed changes between heating and cooling.
22. Replace blower access door and secure with 2 screws
(downflow furnace only).
C. Cleaning Heat Exchanger
The following steps should be performed by a qualified service
technician:
NOTE: Deposits of soot and carbon indicate the existence of a
problem which needs to be corrected. Take action to correct the
problem.
If it becomes necessary to clean the heat exchanger because of
carbon deposits, soot, etc., proceed as follows:
1. Turn off gas and electrical power to furnace.
2. Remove 2 screws from blower access door (downflow
furnace only). Remove control and blower access doors.
3. Remove vent pipe enclosure (downflow furnace only) and
disconnect vent pipe from relief box.
4. Remove 2 screws that secure relief box. (See Fig. 4 or 5.)
5. Disconnect wires to the following components:
a. Draft safeguard switch
b. Inducer motor
c. Pressure switch
d. Limit overtemperature switch
e. Gas valve
f. Edge connector leading to control box
6. Remove 8 screws that secure flue collector box to center
panel. Be careful not to damage sealant.
7. Remove complete inducer assembly from furnace, exposing
flue openings.
8. Clean cells using field-provided small wire brush, steel
spring cable, reversible electric drill, and vacuum cleaner.
a. Assemble wire brush and steel spring cable.
(1.) Use 48 in. of 1/4-in. diameter high-grade steel
spring cable (commonly known as drain clean-out
or Roto- Rooter cable).
(2.) Use 1/4-in. diameter wire brush (commonly known
as 25-caliber rifle cleaning brush).
NOTE: The items needed in steps (1.) and (2.) can usually be
purchased at local hardware stores.
(3.) Insert twisted wire end of brush into end of steel
spring cable, and crimp tight with crimping tool or
strike with ball-peen hammer. TIGHTNESS is very
important.
(4.) Remove metal screw fitting from wire brush to
allow insertion into cable.
b. Clean each heat exchanger cell.
(1.) Attach variable-speed, reversible drill to end of
steel spring cable (end opposite brush).
(2.) Insert brush end of cable into upper opening of cell
and slowly rotate with drill. DO NOT force cable.
Gradually insert at least 36 in. of cable into 2 upper
passes of cell. (See Fig. 6.)
(3.) Work cable in and out of cell 3 or 4 times to obtain
sufficient cleaning. DO NOT pull cable with great
force. Reverse drill and gradually work cable out.
(4.) Remove burner assembly and cell inlet plates.
(5.) Replace screws in center panel and cells before
cleaning.
(6.) Insert brush end of cable in lower opening of cell,
and proceed to clean 2 lower passes of cell in same
manner as 2 upper passes.
(7.) Repeat foregoing procedures until each cell in
furnace has been cleaned.
(8.) Remove residue from each cell using vacuum
cleaner.
(9.) Clean burner assembly using vacuum cleaner with
soft brush attachment.
(10.) Reinstall cell inlet plates and burner assembly.
Care must be exercised to center the burners in the
cell openings.
9. After cleaning flue openings, check sealant on flue collector
to ensure that it has not been damaged. If new sealant is
needed, contact your dealer or distributor.
10. Clean and replace flue collector assembly, making sure all
8 screws are secure.
11. Reinstall 2 screws in relief box.
Fig. 6—Cleaning Heat Exchanger Cell
A91252
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