Flue Gas Passageways; Combustion-Air Blower - Carrier 48FC 08-16 Series Service And Maintenance Instructions

SUPPLY PRESSURE SWITCH
The LP conversion kit includes a supply low pressure switch. The
switch contacts (from terminal C to terminal NO) will open the gas
valve power whenever the supply line pressure drops below the set
point. See Fig. 54 and 55. If the low pressure remains open for 15
minutes during a call for heat, the IGC circuit will initiate a Ignition
Fault (5 flashes) lockout. Reset of the low pressure switch is
automatic on rise in supply line pressure. Reset of the IGC requires
a recycle of unit power after the low pressure switch has closed.
Fig. 54 — LP Low Pressure Switch (Installed)
Fig. 55 — LP Supply Line Low Pressure Switch Wiring
This switch also prevents operation when the propane tank lev-
el is low, which can result in gas with a high concentration of
impurities, additives, and residues that have settled to the bot-
tom of the tank. Operation under these conditions can cause
harm to the heat exchanger system. Contact your fuel supplier
if this condition is suspected.

Flue Gas Passageways

To inspect the flue collector box and upper areas of the heat
exchanger:
1. Remove the combustion blower wheel and motor assembly
according to directions in Combustion-Air Blower section.
See Fig. 56.
2. Remove the vestibule plate to inspect the heat exchanger.
3. Clean all surfaces as required using a wire brush.

Combustion-Air Blower

Clean periodically to assure proper airflow and heating efficiency.
Inspect blower wheel every fall and periodically during heating
season. For the first heating season, inspect blower wheel every
two months to determine proper cleaning frequency.
To access burner section, slide the burner partition panel out of
the unit.
To inspect blower wheel, shine a flashlight into draft hood open-
ing. If cleaning is required, remove motor and wheel as follows:
1. Remove the screw at the base of the burner partition panel
(see Fig. 58) and slide out the panel.
2. Remove the seven screws attaching the induced-draft
motor housing to the vestibule plate. (See Fig. 56.)
3. The blower wheel can be cleaned at this point. If addi-
tional cleaning is required, continue with Steps 4 and 5.
4. Remove the blower from the motor shaft by removing two
setscrews.
5. Removing motor: remove the four screws holding the motor
to the mounting plate. Remove the motor cooling fan by
removing one setscrew. Remove nuts that hold the motor to
the mounting plate.
6. Reverse the procedure outlined above to reinstall the motor.
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