Secondary Heat Exchangers; Flushing Collector Box And Drainage System - Carrier 58MXA Service And Maintenance Instructions

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ELECTRICAL SHOCK AND UNIT DAMAGE
HAZARD
Failure to follow this caution may result in minor personal
injury or furnace component damage.
Label all wires prior to disconnection when servicing con-
trols. Wiring errors can cause improper and dangerous
operation.
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 gas
valve.
8. Disconnect pressure tubing from gas valve.
9. Remove 2 screws attaching top filler panel and rotate upwards
to gain access to screws attaching burner box to cell panel.
10. Remove screws attaching burner box to cell panel. (See Fig.
5.)
NOTE: Burner box cover, manifold, gas valve, and burner
assembly should be removed as 1 assembly.
11. Clean heat exchanger openings with a vacuum and a soft
brush. (See Fig. 6.)
NOTE: After cleaning, inspect the heat exchangers to ensure they
are free of all foreign objects that may restrict flow of combustion
products.
12. Reverse items 4 through 10 for reassembly.
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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.
NOTE: Be sure burner box gasket is installed between burner box
and cell panel. (See Fig. 5.) If gasket is damaged, replace it.
PRIMARY HX
INLET OPENINGS
Fig. 6—Cleaning Inlet Openings of Primary Heat
Exchangers
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 or canola oil, aromatic or
halogenated hydrocarbons or inadequate seal may occur) 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. 7.)
RTV
Fig. 7—Combustion-Air Intake Housing Gasket
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 for
proper tube location. Be sure tubes are not kinked. (See Fig.
8.)
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 transpar-
ent. (See Fig. 9.)
FIRE OR EXPLOSION HAZARD
Failure to follow the safety warnings exactly could result in
serious injury, death, or property damage.
Never test for gas leaks with an open flame. Use a commer-
cially available soap solution made specifically for the
detection of leaks to check all connections. A fire or explo-
sion may result causing property damage, personal injury, or
loss of life.
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 inducer
assembly. See Flushing Collector Box and Drainage System
section for details on removing inducer assembly.
Step 5—Flushing Collector Box and Drainage System
1. Turn off gas and electrical supplies to furnace.
2. Remove main furnace door.
3. Disconnect inducer motor and pressure switch wires or
connectors.
A96305
4. Disconnect pressure switch tubes.
5. Disconnect vent pipe from inducer housing outlet by loosen-
ing coupling clamp on inducer outlet.
6
PAM
Repair
A93087