Carrier SINGLE PACKAGE ROOFTOP UNITS 48PG20-28 Installation And Service Instructions Manual

Also see for 48PG20---28: User's information manual User's information manual Controls, start-up, operation, service and troubleshooting instructions

Carrier SINGLE PACKAGE ROOFTOP UNITS 48PG20-28 Installation And Service Instructions Manual Manual pdf 51 page image

514. Set main gas valve to ON position.5. Set thermostat at setting to call for heat.6. Remove screw cap covering regulator adjustment screw(see Fig. 40).7. Turn adjustment screw clockwise to increase pressure orcounterclockwise to decrease pressure.8. Once desired pressure is established, set unit settingfor no call for heat, turn off main gas valve, removepressure-measuring device, and replace 1/8-in. pipeplug and screw cap.High Altitude — For high altitude applications greaterthan 2000 ft the heat input rate should be reduced. The higherthe altitude is above sea level, the less oxygen is in the air. SeeTable 32 for orifice sizing. A high altitude kit is available toconvert unit for altitudes up to 7,000 ft.Main Burners — For all applications, main burners arefactory set and should require no adjustment.MAIN BURNER REMOVAL1. Shut off (field-supplied) manual main gas valve.2. Shut off power to unit.3. Remove gas section access panel.4. Disconnect gas piping from gas valve inlet.5. Remove wires from gas valve.6. Remove wires from rollout switch.7. Remove sensor wire and ignitor cable from IGC board.8. Remove 2 screws securing manifold bracket to basepan.9. Remove 2 screws that hold the burner assembly to vesti-bule plate.10. Lift burner/manifold assembly out of unit.CLEANING AND ADJUSTMENT1. Remove burner rack from unit as described in MainBurner Removal section above.2. Inspect burners, and if dirty, remove burners from rack.3. Using a soft brush, clean burners and crossover port asrequired.4. Adjust spark gap. See Fig. 41.5. Reinstall burners on rack.6. Reinstall burner rack as described above.OFFON W-1W-2D-1 D-2C1C2PILOTADJ.INLET PRESSURE TAP(PLUGGED)1/8 - 27 N.P.T. THDS.2 LEADS, #18 WIRE 1/32 INSULATION,600V. MAX., 105°CREGULATORADJUSTMENT SCREW(REMOVE COVER)OUTLET PRESSURETAP (PLUGGED)1/8-27 N.P.T. THDS.PILOT CONNECTIONFOR 1/4” O.D. TUBING(PLUGGED)RECEPTACLE ANDTAB COMBINATIONTERMINALRECEPTACLE TERMINALFig. 40 — Gas ValveSEE DETAIL “C”Fig. 41 — Spark Gap Adjustment