Carrier 48TC 17 Series Service And Maintenance Instructions page 45

5. Open the manual shutoff valve, then turn on the unit
main gas valve.
6. Set the room thermostat to call for heat. Verify high−
stage heat operation before attempting to adjust the
manifold pressure.
7. When the main burners ignite, check all fittings, man-
ifold, and orifices for leaks.
8. Adjust the high−stage pressure to the specified setting
by turning the plastic adjustment screw clockwise to
increase pressure, and counterclockwise to decrease
pressure.
9. Set the room thermostat to call for low−stage heat.
Adjust the low−stage pressure to the specified setting.
10. Replace the regulator cover screw(s) when finished.
11. With the burner access panel removed, observe the
unit heating operation in both high stage and low
stage operation. Observe the burner flames to see if
they are blue in appearance, and that the flames are
approximately the same for each burner.
12. Turn off the unit, remove the pressure manometer and
replace the 1/8 in. pipe fitting on the gas manifold.
See Fig. 54.
Burner Ignition
The unit is equipped with a direct spark ignition 100%
lockout system. An Integrated Gas Unit Controller (IGC)
is located in the control box. See Fig. 55. The IGC
contains a self−diagnostic LED (light−emitting diode). A
single LED (see Fig. 59) on the IGC provides a visual
display of operational or sequential problems when the
power supply is uninterrupted. When a break in power
occurs, the IGC will be reset, resulting in a loss of fault
history, and the indoor (evaporator) fan ON/OFF times
will be reset. The LED error code can be observed
through the viewport. During servicing, refer to the label
on the control box cover or Table 12 for an explanation of
LED error code descriptions.
IMORTANT: Refer to the Troubleshooting Tables 17 and
18 for additional information.
If lockout occurs, unit may be reset by interrupting power
supply to unit for at least 5 seconds.
LEGEND
LED - Light Emitting Diode
* A 3-second pause exists between LED error code flashes. If
Orifice Replacement
This unit uses orifice type LH32RFnnn (where nnn
indicates orifice reference size). When replacing unit
orifices, order the necessary parts through the Carrier
Replacement Components Division (RCD). See Table 13
for available orifice sizes. See Tables 15 and 16 for orifice
sizes for Natural Gas and LP fuel usage at various
elevations above sea level. Never drill or plug orifices for
operation.
Check that each replacement orifice is tight at its threads
into the manifold pipe and that orifice projection does not
exceed maximum value. See Fig. 52.
IGNITER AND SENSOR LOCATIONS
(BRACKET HEAT COVER NOT SHOWN FOR CLARIY
9 CELL
50HE400026
0.18" (4.60 mm)
NOTE: SPARK GAP MUST BE AT
Fig. 57 − Typical MRT Spark Adjustment
45
Table 12 – LED Error Code Description*
LED INDICATION
ON
OFF
2 Flashes
3 Flashes
4 Flashes 4 Consecutive Limit Switch Faults
5 Flashes
6 Flashes Induced-Draft Motor Fault
7 Flashes
8 Flashes
9 Flashes
.
more than one error code exists, all applicable codes will be
displayed in numerical sequence.
0.12 - 0.14"
(3.05 - 3.56 mm)
SPARK GAP
THE BOTTOM OF THE BURNER.
ERROR CODE
DESCRIPTION
Normal Operation
Hardware Failure
Limit Switch Fault
Flame Sense Fault
Ignition Lockout Fault
Rollout Switch Fault
Internal Control Fault
Software Lockout
C12546