Burner Ignition; Orifice Replacement - Carrier 48GC04 Service And Maintenance Instructions

GAS VALVE
All three-phase models (except Low NOx) are equipped with 2-
stage gas valves. Single-phase models and all Low NOx models
are equipped with single-stage gas valves. See Fig. 56 for loca-
tions of adjustment screws and features on the gas valves.
To adjust gas valve pressure settings:
IMPORTANT: Leak check all gas connections including
the main service connection, gas valve, gas spuds, and
manifold pipe plug. All leaks must be repaired before firing
unit.
CHECK UNIT OPERATION AND MAKE NECESSARY
ADJUSTMENTS
NOTE: Gas supply pressure at gas valve inlet must be within
specified ranges for fuel type and unit size. See Tables 9 and 10.
1. Slide out burner partition panel.
2. Remove manifold pressure tap plug from manifold and
connect pressure gage or manometer. (See Fig. 53.)
3. Turn on electrical supply.
4. Turn on unit main gas valve.
5. Set room thermostat to call for heat. If unit has two-stage
gas valve, verify high-stage heat operation before attempt-
ing to adjust manifold pressure.
6. When main burners ignite, check all fittings, manifold,
and orifices for leaks.
7. Adjust high-stage pressure to specified setting by turning
the plastic adjustment screw clockwise to increase pres-
sure, counter-clockwise to decrease pressure.
8. For two-stage gas valves, set room thermostat to call for low-
stage heat. Adjust low-stage pressure to specified setting.
9. Replace regulator cover screw(s) when finished.
10. Observe unit heating operation in both high stage and low
stage operation if so equipped. Observe burner flames to
see if they are blue in appearance, and that the flames are
approximately the same for each burner.
11. Turn off unit, remove pressure manometer and replace the
manifold pressure tap plug. (See Fig. 51.)
LIMIT SWITCH
Remove blower access panel. Limit switch is located on the
fan deck. See Fig. 47.

Burner Ignition

Unit is equipped with a direct spark ignition 100% lockout sys-
tem. The Integrated Gas Unit Controller (IGC) is located in the
ON/OFF
SWITCH
NPT INLET
INLET
PRESSURE TAP
NPT OUTLET
SINGLE STAGE
control box (see Fig. 54). The IGC contains a self-diagnostic
LED (light-emitting diode). A single LED (see Fig. 57) on the
IGC provides a visual display of operational or sequential prob-
lems 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 Ta-
ble 11 for an explanation of LED error code descriptions.
If lockout occurs, unit may be reset by interrupting power sup-
ply to unit for at least 5 seconds.
LED — Light Emitting Diode
* A 3-second pause exists between LED error code flashes. If more
than one error code exists, all applicable codes will be displayed in
numerical sequence.
† Indicates a code that is not an error. The unit will continue to operate
when this code is displayed.

Orifice Replacement

This unit uses orifice type LH32RFnnn (where "nnn" indicates
orifice reference size). When replacing unit orifices, order the
necessary parts through RCD. See the High Altitude Gas Con-
version Kit Gas Heating/Electric Cooling 3 to 15 Ton Small
Rooftop Units Accessory LP (Liquid Propane) Installation In-
structions for details.
Ensure each replacement orifice is tight as its threads into the
manifold pipe and the orifice projection does not exceed maxi-
mum value. See Fig. 51.
REGULATOR
COVER SCREW
PLASTIC ADJUST
SCREW
REGULATOR SPRING NPT INLET
(PROPANE - WHITE
NATURAL - SILVER)
GAS PRESSURE PRESSURE TAP
REGULATOR
ADJUSTMENT
MANIFOLD
PRESSURE TAP
Fig. 56 — Typical Gas Valves
32
Table 11 — LED Error Code Descriptions*
LED INDICATION
ON
OFF
1 Flash† Evaporator Fan On/Off Delay Modified
2 Flashes
3 Flashes
4 Flashes 4 Consecutive Limit Switch Faults
5 Flashes
6 Flashes
7 Flashes
8 Flashes
9 Flashes
LEGEND
IMPORTANT: Refer to Tables 12 and 13 for additional trou-
bleshooting information.
ON/OFF
SWITCH
INLET
NPT OUTLET
2 STAGE
ERROR CODE DESCRIPTION
Normal Operation
Hardware Failure
Limit Switch Fault
Flame Sense Fault
Ignition Lockout Fault
Induced-Draft Motor Fault
Rollout Switch Fault
Internal Control Fault
Software Lockout
REGULATOR
COVER SCREW (2)
PLASTIC ADJUST
SCREW (2)
REGULATOR SPRING (2)
(PROPANE - WHITE
NATURAL - SILVER)
LOW STAGE
GAS PRESSURE
REGULATOR
ADJUSTMENT
MANIFOLD
PRESSURE TAP