Cleaning Heat Exchangers; Primary Heat Exchangers; Secondary Heat Exchangers - Carrier 58MCB Service And Maintenance Instructions

WARNING
!
FIRE, EXPLOSION, UNIT DAMAGE HAZARD
Failure to follow this warning could result in personal
injury, death, or property damage.
Gas valve switch MUST be facing forward or tilted
slightly.
19. Replace burner box cover.
20. Turn on gas and electrical supplies to furnace.
WARNING
!
FIRE OR EXPLOSION HAZARD
Failure to follow this warning could result in personal
injury, death or property 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.
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 the 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 orifice(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.
CAUTION
!
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.
3. Disconnect wires or connectors to flame rollout switch, gas
valve, igniter, and flame sensor.
4. Disconnect combustion- -air intake pipe from intake hous-
ing.
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.
9. Remove two screws attaching top filler panel and rotate up-
wards to gain access to screws 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 exchangers to ensure they
are free of all foreign objects that may restrict flow of combustion
products.
PRIMARY HX
INLET OPENINGS
Fig. 8 - - Cleaning Inlet Openings of Primary
Heat Exchangers
CAUTION
!
UNIT MAY NOT OPERATE
Failure to follow this caution may result in improper or
intermittent unit operation.
The ground wire from the gas valve MUST be attached to
the burner box attachment screw.
12. Reverse items 3 through 10 for reassembly.
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.)
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