Carrier 48FC M20 Series Service And Maintenance Instructions page 39

MAIN BURNERS
To access burners, remove the control box access panel and
slide out burner partition panel. At the beginning of each heat-
ing season, inspect for deterioration or blockage due to corro-
sion or other causes. Observe the main burner flames and ad-
just, if necessary.
Orifice projection
Refer to Fig. 50 for maximum projection dimension for orifice
face to manifold tube.
1.00 in.
(25.4 mm)
Manifold
Pipe
Fig. 50 — Orifice Projection
REMOVAL AND REPLACEMENT OF GAS TRAIN
See Fig. 49, 51, 52, 53 and 54.
1. Shut off manual gas valve.
2. Shut off power to unit.
3. Remove the indoor blower access panel.
4. Remove the gas access panel.
Gas Limit Switch
Side Shot
Gas Limit Switch
Down Shot
Fig. 51 — Heat Exchanger Access - Gas Limit Switches and HX Rack Locations
Orifice
Supply Base Pan
39
5. Remove the screws at the base of the burner partition
panel (see Fig. 53) and slide out the panel.
6. Disconnect gas piping at unit gas valve.
7. Remove wires connected to gas valve. Mark each wire.
8. Remove igniter wires and sensor wires at the Integrated
Gas Unit Controller (IGC). (See Fig. 54.)
9. Remove the two screws attaching the burner rack to the
vestibule plate (see Fig. 49).
10. Slide the burner tray out of the unit. (See Fig. 52.)
11. Reverse the procedures outlined above to reinstall the
burner rack.
CLEANING AND ADJUSTMENT
1. Remove burner rack from unit as described in "Removal
and Replacement of Gas Train" section.
2. Inspect burners; if dirty, remove burners from rack. (Mark
each burner to identify its position before removing from
the rack.)
3. Use a soft brush to clean burners and cross-over port as
required.
4. Adjust spark gap. (See Fig. 55.)
5. If factory orifice has been removed, check that each orifice
is tight at its threads into the manifold pipe and that orifice
projection does not exceed maximum value. (See Fig. 50.)
6. Reinstall burners on rack in the same locations as factory-
installed. (The outside crossover flame regions of the out-
ermost burners are pinched off to prevent excessive gas
flow from the side of the burner assembly. If the pinched
crossovers are installed between two burners, the flame
will not ignite properly.)
7. Reinstall burner rack as described in "Removal and
Replacement of Gas Train" section.
Heater Tube Assembly
Heat Exchanger (HX) Rack
Outdoor Base Pan