41
b. Remove screws securing cutoff plate and remove cutoff
plate from housing.
c. Loosen set screw holding blower wheel on motor shaft
(160+/-- 20 in.--lb. when reassembling).
d. Removeboltsholding motor to blower housing and slide
motor out of wheel(40+/--10 in.--lb. whenreassembling).
e. Remove blower wheel from housing.
f. Clean wheel and housing.
10. Reassemble motor and blower by reversing steps 9f
through 11a, finishing with 9a. Be sure to reattach ground
wire to the blower housing.
11. Verify that blower wheel is centered in blower housing
and set screw contacts the flat portion of the motor shaft.
Loosen set screw on blower wheel and reposition if neces-
sary .
12. Spin the blower wheel by hand to verify that the wheel
does not rub on the housing.
13. Reinstall blower assembly in furnace.
14. Reinstall two screws securing blower assembly to blower
deck.
UNIT DAMAGE HAZARD
Failure to follow this caution may result in shortened heat
exchanger life.
Heating fan speed(s) MUST be adjusted to provide proper
air temperature rise as specified on the rating plate.
Recommended operation is at the midpoint of the rise range
or slightly above. Refer to “SET TEMPERATURE RISE”
under START --UP, ADJUSTMENT, and SAFETY
CHECK.
CAUTION
!
NOTE: Refer to Table 5 for motor speed lead relocation if leads
were not identified before disconnection.
15. Refer to furnace wiring diagram, and connect thermostat
leads if previously disconnected.
16. To check blower for proper rotation:
a. Turn on electrical supply.
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal
injury, or death.
Blower access door switch opens 115--v power to
furnace control. No component operation can occur
unless switch is closed. Exercise caution to avoid
electrical shock from exposed electrical components
when manually closing this switch for service purposes.
!
WARNING
b. Manually close blower access door switch.
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.
c. Perform component self--test as shown at the bottom of
the SERVICE label, located on the front of blower access
door.
d. Verify blower is rotating in the correct direction.
17. If furnace is operating properly, RELEASE BLOWER
ACCESS DOOR SWITCH. Remove any jumpers o r re-
connect any disconnected thermostat leads. Replace blow-
er access door.
18. Downflow or horizontal furnaces with vent pipe through
furnace only:
a. Installand connect short piece of ventpipe inside furnace
to existing vent.
b. Connect vent connector to vent elbow.
19. Reinstall outer door.
20. Cycle furnace through one complete heating and cooling
cycle. Verify the furnace temperature rise as shown in
“Adjustments” Section. Adjust temperature rise as shown
in “Adjustments” Section. If outdoor temperature is below
70_F, (21_C) turn off circuit breaker to outdoor unit be-
fore running furnace in the cooling cycle. Turn outdoor
circuit breaker on after completing cooling cycle.
CLEANING HEAT
EXCHANGER
The following steps should be performed by a qualified
service agency:
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 heavy 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, remove internal vent pipe within the casing.
5. Disconnect wires to the following components. Mark
wires to aid in reconnection of (be careful when discon-
necting wires from switches because damage may occur):
a. Draft safeguard switch.
b. Inducer motor.
c. Pressure switch(es).
d. Limit over--temperature switch.
e. Gas valve.
f. Hot surface igniter.
g. Flame--sensing electrode.
h. Flame rollout switches.
6. Remove screws that fasten the collector box assembly to
the cell panel. Be careful not to damage the collector box.
Inducer assembly and elbow need not be removed from
collector box.
7. Disconnect gas line from gas manifold.
8. Remove the 5 screws that attach the burner assembly to
the cell panel. The gas valve and individual burners need
not be removed from support assembly. Remove NOx baf-
fles if installed.
NOTE: Be very careful when removing burner assembly to
avoid breaking igniter. See Fig. 45 and 46 for correct igniter
location.
9. Using field--provided 25--caliber rifle cleaning brush,
36--in. (914 mm) long, 1/4” (6 mm) diameter steel spring
cable, a variable speed, reversible electric drill, and vacu-
um cleaner, clean cells as follows:
a. Remove metal screw fitting from wire brush to allow in-
sertion into cable.
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