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21. Check for gas leaks.
22. Replace main furnace door.
Step 4 — Cleaning Heat Exchangers
The following items should be performed by a qualified service
technician.
PRIMARY HEAT EXCHANGERS
If the heat exchangers get an accumulation of light dirt or dust on
the inside, they may be cleaned by the following procedure:
NOTE: If heat exchangers get a heavy accumulation of soot and
carbon, both the primary and secondary heat exchangers should be
replaced rather than trying to clean them thoroughly due to their
intricate design. 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, improper vent termination, incorrect size or
damaged manifold orifices(s), improper gas, or a restricted heat
exchanger (primary or secondary). Action must be taken to correct
the problem.
1. Turn off gas and electrical supplies to furnace.
2. Remove main furnace door.
UNIT DAMAGE HAZARD
Failure to follow this caution may result in furnace component
damage.
Label all wires prior to disconnection when servicing controls.
Wiring errors can cause improper and hazardous operation.
CAUTION
!
3. Disconnect wires or connectors to flame rollout switch, gas
valve, igniter, and flame sensor.
4. Disconnect combustion-air intake pipe from intake housing.
5. Remove the pressure switch tube from intake housing.
6. Remove screws attaching intake housing to burner box, and
rotate intake housing away from burner box for removal.
7. Using backup wrench, disconnect gas supply pipe from fur-
nace gas control valve.
8. Disconnect pressure tubing from gas valve.
PRIMARY HX
INLET OPENINGS
A96305
Fig. 8 -- Cleaning Inlet Openings of Primary
Heat Exchangers
9. Remove 2 s crews attaching top filler panel and rotate up-
wards to gain access to s crews attaching burner box to cell
panel.
10. Remove screws attaching burner box to cell panel. (See Fig.
6).
NOTE: Burner box, cover, manifold, gas valve, and burner
assembly should be removed as one assembly.
11. Clean heat exchanger openings with a vacuum and a soft
brush. (See Fig. 8.)
NOTE: After cleaning, inspect the heat exchanger to ensure they
are free of all foreign objects that may restrict flow of combustion
products.
12. Reverse items 4 through 10 for reassembly.
UNIT MAY NOT OPERATE
Failure to attach this ground wire to an adequate casing
ground may cause the furnace control to lock out.
The ground wire from the gas valve MUST be attached to the
burner box attachment screw.
CAUTION
!
NOTE: Be sure burner box gasket is installed between burner box
and cell panel. (See Fig. 6.) If gasket is damaged, replace it.
NOTE: Inspect combustion-- air intake housing. If foamed gasket
was removed, check for any damage. If gasket is damaged in any
way, it must be repaired. To repair, remove damaged gasket
section, apply sealant releasing agent such as PAM cooking spray
or equivalent (must not contain corn nor canola oil, halogenated
hydrocarbons nor aromatic content, to prevent inadequate seal
from occurring) to burner box and apply a small bead of G.E. RTV
162, G.E. RTV 6702, or Dow -- Corning RTV 738 sealant to edge
of combustion-- air intake housing. (See Fig. 9.)
13. Refer to furnace wiring diagram and reconnect wires to
flame rollout switch, gas valve, igniter, and flame sensor.
14. Reconnect pressure switch tubes to gas valve and intake
housing. Refer to tube routing label on main furnace door
or Fig. 10 for proper tube location. Be sure tubes are not
kinked.
15. Turn on gas and electrical supplies to furnace.
16. Check furnace operation through 2 complete heat operating
cycles. Look through sight glass in burner enclosure to
check burners. Burner flames should be clear blue, almost
transparent. (See Fig. 11.)
FIRE OR EXPLOSION HAZARD
Failure to follow this safety warning could result in personal
injury, death, orproperty damage.
Never test for gas leaks with an open flame. Use a
commercially available soap solution made specifically for the
detection of leaks to check all connections.
!
WARNING
17. Check for gas leaks.
18. Replace main furnace door.
SECONDARY HEAT EXCHANGERS
NOTE: The condensing side (inside) of the secondary heat
exchangers CANNOT be serviced or inspected. A small number
of bottom outlet openings can be inspected by removing the
58MEC