g. Remove blower wheel from housing.
CAUTION:
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.
CAUTION:
Heating air speed selection MUST be ad-
justed to provide proper air temperature rise as specified
on the rating plate. Failure to adjust the heating speed
may shorten heat exchanger life. Recommended opera-
tion 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.
WARNING:
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 warn-
ing 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
RELEASE BLOWER ACCESS DOOR SWITCH, and then
replace blower access door.
III. 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.
(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 materials needed in items (1.) and (2.) can usually be
purchased at local hardware stores.
(3.) Insert twisted wire end of brush into end of 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
spring cable (end opposite brush).
(2.) Insert brush end of cable into the outlet 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. 5.)
(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.
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.
—4—
