Bryant 986TB Installation, Start-Up, Operating And Service And Maintenance Instructions page 82

3. All factory wires can be left connected, but field thermostat
and accessory wiring may need to be disconnected depend-
ing on their length and routing.
4. If the vent and combustion air pipe passes through the
blower compartment, it will be necessary to remove the
pipes from the blower compartment.
Disconnect the vent and combustion air pipe by:
a. Loosen the clamps on the vent couplings and combustion
air pipe external to the furnace.
b. Separate the pipes from the couplings and move them
aside.
c. Loosen the clamps on the vent couplings and combustion
air pipe located on the blower shelf.
d. Separate the pipes from the blower compartment and set
aside.
e. Remove the couplings from the pipe adapters and set aside.
f. After servicing the blower, reverse steps a through e.
g. Tighten all clamps 15 lb −in.
See Fig. 70 for Steps 5 through 14.
5. Remove screws securing blower assembly to blower shelf
and slide blower assembly out of furnace. Detach ground
wire and disconnect blower motor harness plugs from
blower motor.
NOTE: Blower wheel is fragile. Use care.
6. Clean blower wheel and motor by using a vacuum with soft
brush attachment. Be careful not to disturb balance weights
(clips) on blower wheel vanes. Do not bend wheel or blades
as balance will be affected.
7. If 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 and blower housing so each
arm is positioned at the same hole 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. Remove bolts holding motor mounts to blower housing
and slide motor and mounts out of housing.
f. Remove blower wheel from housing.
g. Clean wheel per instructions on degreaser cleaner. Do not
get degreaser in motor.
8. Reassemble motor and blower wheel by reversing items 7b
through 7f. Ensure wheel is positioned for proper rotation.
9. Torque motor mounting bolts to 40 +/− 10 lb−in. when reas-
sembling.
10. Torque blower wheel set screw to 160 +/− 20 lb−in. when
reassembling.
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 necessary.
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 2 screws securing blower assembly to blower
deck.
15. Reconnect blower leads to furnace control. Refer to furnace
wiring diagram, and connect thermostat leads if previously
disconnected.
NOTE: Be sure to attach ground wire and reconnect blower
harness plugs to blower motor.
WARNING
!
ELECTRICAL OPERATION HAZARD
Failure to follow this warning could result in personal injury
or death.
Blower door switch opens 115−v power to control. No
component operation can occur unless switch is closed.
Caution must be taken when manually closing this switch for
service purposes.
16. Downflow or horizontal furnaces with vent pipe through
furnace only:
a. Install and connect short piece of vent pipe inside furnace
to existing vent.
b. Connect vent connector to vent elbow.
17. Turn on electrical supply. Manually close blower 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 G and R to Y/Y2 on furnace
control thermostat terminals. If outdoor temperature is be-
low 70_F, turn off circuit breaker to outdoor unit before
running furnace in the cooling cycle. Turn outdoor circuit
breaker on after completing cooling cycle. See Fig. 38.
NOTE: If R−W/W1 thermostat terminals are jumpered at the time
blower door switch is closed, blower will run for 90 sec before
beginning a heating cycle.
a. Perform component self−test as shown at the bottom of the
SERVICE label, located on the control door.
b. Verify blower is rotating in the correct direction
18. If furnace is operating properly, RELEASE BLOWER
DOOR SWITCH. Remove any jumpers or reconnect any
disconnected thermostat leads. Replace blower door.
19. Turn on gas supply and cycle furnace through one complete
heating cycle. Verify the furnace temperature rise as shown
in Adjustments Section. Adjust temperature rise as shown in
Adjustments Section.
Cleaning Burners and Flame Sensor
The following items must be performed by a qualified service
technician. If the burners develop an accumulation of light dirt or
dust, they may be cleaned by using the following procedure:
NOTE: Use a back-up wrench on the gas valve to prevent the
valve from rotating on the manifold or damaging the mounting to
the burner assembly.
WARNING
!
ELECTRICAL SHOCK AND FIRE HAZARD
Failure to follow this warning could result in personal injury,
death, and/or property damage.
Turn off the gas and electrical supplies to the furnace and
install lockout tag before performing any maintenance or
service. Follow the operating instructions on the label
attached to the furnace.
Refer to Fig. 71.
1. Disconnect power at external disconnect, fuse or circuit
breaker.
2. Turn off gas at external shut-off or gas meter.
3. Remove control door and set aside.
4. Turn electric switch on gas valve to OFF.
5. Disconnect the gas pipe from gas valve and remove pipe
from the furnace casing.
6. Remove individual wires from terminals on gas valve.
7. Disconnect Hot Surface Igniter (HSI) wires from HSI.
8. Disconnect Flame Sensor wire from Flame Sensor.
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