45
441 01 2121 01
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 R−W/W1 thermostat terminals are jumpered at the
time blower access door switch is closed, blower will run for
90 sec before beginning a heating cycle.
c. Perform component self−test as shown at the bot-
tom 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 or re-
connect any disconnected thermostat leads. Replace
blower access door.
18. 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.
19. Reinstall outer door.
20. Turn on gas supply and cycle furnace through one
complete heating and cooling cycle. Verify the furnace
temperature rise as shown in Adjustments Section. Ad-
just temperature rise as shown in Adjustments Section.
If outdoor temperature is below 70F, 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 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 (be careful when discon-
necting wires from switches because damage may oc-
cur):
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 collector box assembly
to the cell panel. Be careful not to damage the collector
box. Inducer assembly and elbow need not be re-
moved from collector box.
7. Disconnect gas line from gas manifold.
8. Remove the four screws that attach the burner as-
sembly to the cell panel. The gas valve and individual
burners need not be removed from support assembly.
Remove NOx baffles, if installed.
NOTE: Be very careful when removing burner assembly to
avoid breaking igniter. See Figure 52−Figure 53 for correct
igniter location.
9. Using field−provided 25−caliber rifle cleaning brush,
36−in. (914 mm) long, 1/4−in. (6 mm) diameter steel
spring cable, a variable speed reversible electric drill,
and vacuum cleaner, clean cells as follows:
Figure 52 − Igniter Position − Side View
A05025
Figure 53 − Igniter Position − Top View
A05026
a. Remove metal screw fitting from wire brush to allow
insertion into cable.
b. Insert the twisted wire end of brush into end of
spring cable, and crimp tight with crimping tool or
crimp by striking with ball−peen hammer. TIGHT-
NESS IS VERY IMPORTANT.
NOTE: The materials needed in item 9 can usually be
purchased at local hardware stores.
(1.) Attach variable−speed, reversible drill to the
end of spring cable (end opposite brush).
(2.) Insert brush end of cable into the outlet open-
ing of cell and slowly rotate with drill. DO NOT
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