Secondary Heat Exchangers; Flush Collector Box And Drainage System; Service Hot Surface Ignitor; Electrical Controls And Wiring - Carrier 58MCA Service And Maintenance Instructions

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. 10.)
17. Check for gas leaks.
Never use matches, candles, flame, or other sources of
ignition to check for gas leakage. Use a soap-and-water
solution. Failure to follow this warning could result in a fire,
personal injury, or death.
18. Replace 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 Step 5 — Flush Collector Box and Drainage System
for details on removing inducer assembly.
Step 5—Flush Collector Box and Drainage System
1. Turn off gas and electrical supplies to furnace.
2. Remove furnace door.
3. Disconnect inducer motor and pressure switch(es) wires or
connectors.
4. Disconnect pressure switch tubes.
5. Disconnect vent pipe from inducer housing outlet by loosen-
ing clamp.
6. Disconnect drain tube from inducer housing. (See Fig. 8 or 9.)
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.
10. Reassemble inducer assembly by reversing items 5. through 7.
NOTE: If seal between the inducer housing and the collector box
is damaged in any way, it must be repaired. To repair, apply
sealant releasing agent (PAM cooking spray or equivalent, must
not contain corn or canola oil, aromatic or halogenated hydrocar-
bons) to inducer housing. (See Fig. 11.) Apply a small bead of G.E.
RTV 162 or Dow-Corning RTV 738 sealant to groove in collector
box.
11. Refer to furnace wiring diagram and connect wires to inducer
motor and pressure switch(es) or connectors.
12. Reconnect pressure tubes to pressure switch(es). See diagram
on main furnace door for proper location of tubes. Be sure
tubes are not kinked. (See Fig. 8 or 9.)
13. Turn on gas and electrical supplies to furnace.
14. Check furnace operation through 2 complete heat operating
cycles. Check area below inducer housing, vent pipe, and
condensate trap to ensure no condensate leaks occur. If leaks
are found, correct the problem.
15. Check for gas leaks.
Never use matches, candles, flame, or other sources of
ignition to check for gas leakage. Use a soap-and-water
solution. Failure to follow this warning could result in a fire,
personal injury, or death.
16. Replace furnace door.
Step 6—Service Hot Surface Ignitor
The ignitor does NOT require annual inspection. Check ignitor
resistance before removal.
1. Turn off gas and electrical supplies to furnace.
2. Remove furnace door.
3. Disconnect ignitor wire connection.
4. Check ignitor resistance.
a. Using an ohm meter, check resistance across both ignitor
leads in connector.
b. Cold reading should be between 45 ohms and 90 ohms.
c. If ohm reading is higher than 110 ohms, ignitor is cracked
and must be replaced.
5. Remove ignitor.
a. While spreading ignitor bracket legs outward, use hand to
GENTLY guide ignitor out of burner box.
The ignitor is fragile. DO NOT allow it to hit the side of the
burner box opening while removing or replacing it.
b. Inspect ignitor for a white area indicating a crack may be
present. If found, replace ignitor.
NOTE: A small crack cannot be seen on a new ignitor. After a
period of operation, a white area will be visible around the crack.
6. After inspecting or replacing ignitor, install it into burner box
by gently pushing ignitor into bracket until bracket legs fully
secure ignitor. (See Fig 12.)
7. Connect ignitor wire connection.
8. Turn on gas and electrical supplies to furnace.
9. Check furnace operation through 2 heat operating cycles.
10. Replace furnace door.
Step 7—Electrical Controls and Wiring
There may be more than 1 electrical supply to the unit. Check
accessories and cooling unit for additional electrical supplies.
The electrical ground and polarity for 115-v wiring must be
maintained properly. Refer to Fig. 13 for field wiring information
and to Fig. 18 or 22 for unit wiring information.
NOTE: If the polarity is not correct, the STATUS LED on the
control center will flash rapidly and prevent the furnace from
operating. The control system also requires an earth ground for
proper operation of the control center and flame sensing.
The 24-v circuit contains an automotive-type, 3-amp fuse located
on the control center. (See Fig. 14 and 15.) Any direct shorts of the
24-v wiring during installation, service, or maintenance will cause
this fuse to blow. If fuse replacement is required, use ONLY a fuse
of identical size.
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