Carrier 48TM016-028 Installation, Start-up And Service Instructions Manual

Also see for 48TM016: User's information manual

Contents

46Gas Valve AdjustmentNATURAL GAS — The gas valve opens and closes inresponse to the thermostat or limit control.When power is supplied to valve terminals D1 and C2, themain valve opens to its preset position.The regular factory setting is stamped on the valve body(3.3 in. wg).To adjust regulator:1. Set thermostat at setting for no call for heat.2. Turn main gas valve to OFF position.3. Remove 1/8-in. pipe plug from manifold or gas valvepressure tap connection. Install a suitable pressure-measuring device.4. 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. 55).7. Turn adjustment screw clockwise to increase pressure orcounterclockwise to decrease pressure.8. Once desired pressure is established, set thermostat set-ting for no call for heat, turn off main gas valve, removepressure-measuring device, and replace 1/8-in. pipe plugand screw cap.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 unit control box access panel, burner sectionaccess panel, and center post (Fig. 4-6).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 support plateflange to the vestibule plate.10. Lift burner 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. 56.5. Reinstall burners on rack.6. Reinstall burner rack as described above.Filter Drier — Replace whenever refrigerant system isexposed to atmosphere.Protective DevicesCOMPRESSOR PROTECTIONOvercurrent — Each compressor has internal line break motorprotection.Crankcase Heater — All units are equipped with a 70-wattcrankcase heater to prevent absorption of liquid refrigerant byoil in the crankcase when the compressor is idle. The crank-case heater is energized whenever there is a main power to theunit and the compressor is not energized.Compressor Lockout — If any of the safeties (high-pressure,low-pressure, freeze protection thermostat, compressor internalthermostat) trip, or if there is loss of power to the compressors,the cooling lockout (CLO) will lock the compressors off. Toreset, manually move the thermostat setting.EVAPORATOR-FAN MOTOR PROTECTION — A man-ual reset, calibrated trip, magnetic circuit breaker protectsagainst overcurrent. Do not bypass connections or increase thesize of the breaker to correct trouble. Determine the cause andcorrect it before resetting the breaker.CONDENSER-FAN MOTOR PROTECTION — Eachcondenser-fan motor is internally protected againstovertemperature.HIGH-PRESSURE AND LOW-PRESSURE SWITCHES —If either switch trips, or if the compressor overtemperatureswitch activates, that refrigerant circuit will be automaticallylocked out by the CLO. To reset, manually move the thermo-stat setting.FREEZE PROTECTION THERMOSTAT (FPT) — An FPTis located on the top and bottom of the evaporator coil. Theydetect frost build-up and turn off the compressor, allowing thecoil to clear. Once the frost has melted, the compressor can bereenergized by resetting the compressor lockout.Relief Devices — All units have relief devices to protectagainst damage from excessive pressures (i.e., fire). Thesedevices protect the high and low side.Control Circuit, 24-V — This control circuit is pro-tected against overcurrent by a 3.2 amp circuit breaker.Breaker can be reset. If it trips, determine cause of troublebefore resetting. See Fig. 57 and 58 for typical wiringdiagrams.Replacement Parts — A complete list of replacementparts may be obtained from any Carrier distributor uponrequest.IMPORTANT: After a prolonged shutdown or servicing,energize the crankcase heaters for 24 hours before start-ing the compressors.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. 55 — Gas Valve