10. If a greasy residue is present on blower wheel, remove wheel
from the blower housing and wash it with an appropriate
degreaser. To remove wheel:
a. Mark blower wheel location on shaft before disassembly to
ensure proper reassembly.
b. Loosen setscrew holding blower wheel on motor shaft.
NOTE:
Mark blower mounting arms, motor, and blower housing
so motor and each arm is positioned at the same location during
reassembly.
c. Mark blower wheel orientation and cutoff plate location to
ensure proper reassembly.
d. Remove screws securing cutoff plate and remove cutoff
plate from housing.
e. Disconnect capacitor and ground wire attached to blower
housing before removing motor.
f. Remove bolts holding motor and motor mounts to blower
housing and slide motor and mounts out of housing. Motor
mount belly band need not be removed unless motor is to be
replaced.
g. Remove blower wheel from housing.
The blower wheel should not be dropped or bent as balance
will be affected.
11. Reassemble motor and blower by reversing items 9a through
9g. Be sure to reattach ground wire.
12. Reinstall blower assembly in furnace.
13. Reinstall control and transformer support assembly in furnace.
14. Reconnect blower leads to furnace control.
Refer to furnace wiring diagram, and connect thermostat leads
if previously disconnected. (See Fig. 7.)
NOTE:
Refer to Table 2 for motor speed lead relocation if leads
were not identified before disconnection.
Heating air speed selection MUST be adjusted to provide
proper air temperature rise as specified on the rating plate.
Failure to adjust the heating speed may shorten heat ex-
changer life. Recommended operation is at the midpoint of
rise range or above.
15. Downflow or horizontal furnaces with vent pipe through
furnace only: Reinstall internal vent pipe by reversing items 3a
and 3b.
16. Reinstall vent connector to furnace vent elbow. Securely
fasten vent connector to vent elbow with 2 field-supplied,
corrosion-resistant, sheet metal screws located 180° apart.
17. Turn on electrical supply. Manually close blower access door
switch. Use a piece of tape to hold switch closed. Check for
proper rotation and speed changes between heating and
cooling by jumpering R-to-W/W1 R-to-W/W1-and-W2, and
then R-to-Y on furnace control thermostat terminals.
Blower access door switch opens 115-v power to furnace
control. No component operation can occur. Caution must be
taken when manually closing this switch for service purposes.
Failure to follow this warning could result in electrical shock,
personal injury, or death.
NOTE:
If thermostat terminals are jumpered at the time blower
access door switch is closed, blower will run for 90 sec before
beginning a heating or cooling cycle.
18. If furnace is operating properly, REMOVE TAPE TO RE-
LEASE BLOWER ACCESS DOOR SWITCH, and then
replace blower access door.
Step 3—Cleaning Heat Exchanger
The following steps should be performed by a qualified service
technician:
NOTE:
If the heat exchangers get a heavy accumulation of soot
and carbon, they should be replaced rather than trying to clean
them thoroughly. A build-up of soot and carbon indicates that a
problem exists which needs to be corrected, such as improper
adjustment of manifold pressure, insufficient or poor quality
combustion air, incorrect size or damaged manifold orifice(s),
improper gas, or a restricted heat exchanger. Action must be taken
to correct the problem.
If it becomes necessary to clean the heat exchangers because of
dust or corrosion, proceed as follows:
1. Turn OFF gas and electrical power to furnace.
2. Remove outer access door.
3. Disconnect vent connector from furnace vent elbow.
4. For downflow or horizontal furnace having an internal vent
pipe, disconnect internal vent pipe within the casing.
5. Disconnect wires to the following components. Mark wires to
aid in reconnection of:
a. Draft safeguard switch.
b. Inducer motor.
c. Pressure switches.
d. Limit overtemperature switch.
e. Gas valve.
f. Hot surface igniter.
g. Flame-sensing electrode
h. Flame rollout switches.
6. Remove screws that fasten the inducer assembly with backing
plate to the cell panel. Be careful not to damage backing plate.
Inducer assembly and elbow need not be removed from
backing plate.
7. Remove burner, gas manifold and support assembly and NOx
devices if present. Individual burners need not be removed
from support assembly.
NOTE:
Be very careful when removing burner assembly to avoid
breaking igniter. See Fig. 4 for correct igniter location.
8. Using field-provided small wire brush, steel spring cable,
reversible electric drill, and vacuum cleaner, clean cells as
follows:
a. Assemble wire brush and steel spring cable.
TABLE 2—SPEED SELECTOR
COLOR
SPEED
FACTORY-
ATTACHED
TO
White
Common
BLW
Black
High
COOL
Yellow (When Present)
Medium High
SPARE
Orange†
Medium
SPARE
Blue
Medium Low
HI HEAT
Red
Low
LO HEAT
† Available on 5-speed blowers only.
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