Secondary Heat Exchangers; Flushing Collector Box And Drainage System - Carrier 58MTA Service Manual

PRIMARY HX
INLET OPENINGS
Fig. 6—Cleaning Inlet Openings of Primary Heat
Exchangers
The ground wire from the gas valve MUST be attached to the
burner box attachment screw. Failure to attach this ground
wire to an adequate casing ground will cause the furnace
control to lock out.
NOTE: Be sure burner box gasket is installed between burner box
and cell panel. (See Fig. 5.) 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 or canola oil, aromatic or
halogenated hydrocarbons which can cause an inadequate seal to
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 Repair
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. 8 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 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
A96305
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.
4. Disconnect pressure switch tubes.
5. Disconnect vent pipe from inducer housing outlet by loosen-
ing coupling clamp on inducer outlet.
6. Disconnect drain tube from inducer housing. (See Fig. 8.)
7. Remove inducer housing assembly by removing 4 bolts
attaching assembly to cell panel.
8. Flush inside of collector box with water until discharge from
condensate trap is clean and runs freely.
NOTE: Ensure the drain tube disconnected from the inducer
housing is higher than the collector box opening or water will flow
out tube.
9. Inspect inside area of collector box for any pieces of foreign
materials and remove if present.
DO NOT use wire brush or other sharp object to inspect or
dislodge materials in secondary heat exchangers as failure of
the secondary heat exchanger will occur. Flush with water
only.
PAM
10. Reassemble inducer assembly by reversing items 5-7. Tighten
vent coupling clamp screw(s) to 15 in.-lb of torque.
NOTE: If seal between the inducer housing and the collector box
A93087
is damaged in any way, it must be repaired. To repair, apply
sealant releasing agent such as PAM cooking spray or equivalent
(must not contain corn or canola oil, aromatic or halogenated
hydrocarbons which can cause an inadequate seal to occur) to
inducer housing. (See Fig. 10.) Apply a small bead of G.E. RTV
162, G.E. RTV 6702, or Dow-Corning RTV 738 sealant to groove
in collector box. (See Fig. 10.)
11. Refer to furnace wiring diagram and reconnect wires to
inducer motor and pressure switches or connectors.
12. Reconnect pressure tubes to pressure switches. See diagram
on main furnace door for proper location of tubes. Be sure
tubes are not kinked. (See Fig. 8.)
13. Turn on gas and electrical supplies to furnace.
6