Cleaning Heat Exchanger - Carrier 120/C Series Installation, Start-Up, Operating And Service And Maintenance Instructions

To ensure long life and high efficiency, clean accumulated dirt and
grease from blower wheel and motor annually.
The inducer and blower motors are pre-lubricated and require no
additional lubrication. These motors can be identified by the
absence of oil ports on each end of the motor.
Clean blower motor and wheel as follows:
1. Turn off electrical supply to furnace.
2. Loosen the thumbscrew on outer door and remove outer door.
3. For downflow or horizontal furnaces having vent pipes within
the furnace that pass in front of the blower access door:
a. Disconnect vent connector from furnace vent elbow.
b. Disconnect and remove short piece of vent pipe from
within furnace.
4. Remove 2 screws from blower access door and remove blower
access door.
5. Disconnect blower leads from furnace control. Record wire
color and location for reassembly. All other factory wires can
be left connected, but field thermostat connections may need
to be disconnected depending on their length and routing.
6. Remove 2 screws holding control box to blower shelf.
7. Hang control box from front of furnace casing and away from
blower compartment.
8. Remove 2 screws holding blower assembly to blower deck
and slide blower assembly out of furnace.
9. Clean blower wheel and motor using a vacuum with soft brush
attachment. Blower wheel blades may be cleaned with a small
paint or flux brush. Do not remove or disturb balance weights
(clips) on blower wheel blades.
10. Vacuum any loose dust from blower housing, wheel and
motor.
11. 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:
NOTE: Before disassembly, mark blower motor, and blower
housing so motor and each arm is positioned at the same location
during reassembly.
a. Disconnect capacitor wires and ground wire attached to
blower housing.
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. Remove bolts holding motor to blower housing and slide
motor out of wheel (40+/-10 in.-lb. when reassembling).
e. Remove blower wheel from housing.
f. Clean wheel and housing.
12. Reassemble motor and blower by reversing steps 11f through
11a, finishing with 11a. Be sure to reattach ground wire to the
blower housing.
13. 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.
14. Spin the blower wheel by hand to verify that the wheel does
not rub on the housing.
15. Reinstall blower assembly in furnace.
16. Reinstall control box assembly in furnace.
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. Recom-
mended operation is at the midpoint of the rise range or
slightly above. Refer to "SET TEMPERATURE RISE" under
START-UP, ADJUSTMENT, and SAFETY CHECK.
NOTE: Refer to Table 9 for motor speed lead relocation if leads
were not identified before disconnection.
17. Reconnect blower leads to furnace control. Refer to furnace
wiring diagram, and connect thermostat leads if previously
disconnected.
18. 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.
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
19. If furnace is operating properly, RELEASE BLOWER AC-
CESS DOOR SWITCH. Remove any jumpers or reconnect
any disconnected thermostat leads. Replace blower access
door.
20. 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.
21. Reinstall casing door.
22. Turn on gas supply and 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, turn off circuit breaker to outdoor unit before
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
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