g43 service manual - Heating and Air Parts

I−High AltitudeNOTE − In Canada, certification for installations at elevationsover 4500 feet (1372 m) is the jurisdiction of local authorities.The manifold pressure may require adjustment to ensureproper operation at higher altitudes. Refer to table 19 forproper manifold pressure settings at varying altitudes.Table 20 lists required pressure switch changes and conversionkits at varying altitudes.The combustion air pressure switches are factory−set andrequire no adjustment.ModelInputSizeGasFuelNat.GasNat.GasTABLE 19Manifold Pressure (Outlet) inches w.c.ModelAltitude (feet)InputSizes0−45004501−55005501−65006501−75007501−10,000045,070,090,3.5 3.5 3.5 3.5 3.5*110135 3.5 3.3 3.2 3.1 3.5*135−4andlater3.5 3.5 3.5 3.5 3.5*All10.0** 10.0** 10.0** 10.0** 10.0**L.P.Gas sizes* Conversion kit required for applications at altitudes above7501 ft. above sea level.** Conversion kit required for all applications at all altitudes.TABLE 20Conversion Kit and Pressure Switch Requirements at Varying AltitudesAltitude0 − 4500 ft.(0 − 1372 m)Required PressureConversion Kit Switch4,501 − 7500 ft.(1373 − 2286 m)Required PressureConversion Kit Switch7501−10,000 ft.(2287 − 3048 m)Required PressureConversion Kit SwitchRequired Pressure Required Pressure Required Pressure−045 Nat. N/A No Change N/A No Change 59M16 56M06−070 LPG 83M74 No Change 83M74 No Change 83M75 56M06−045−7 and later Nat. N/A No Change N/A No Change N/A 95M22LPG 83M74 No Change 83M74 No Change 83M75 56M06−070−7 7 and later Nat. N/A No Change N/A 56M05 N/A 56M06LPG 83M74 No Change 83M74 No Change 83M75 56M06−090 Nat. N/A No Change N/A 75M20 59M16 56M07−110 LPG 83M74 No Change 83M74 75M20 83M75 56M07−135−1, −2, −3Nat. N/A No Change N/A 56M04 47M82 60M35LPG 83M74 No Change 83M74 56M04 83M75 60M35−135−4 Nat. N/A No Change N/A 56M04 59M16 60M35and later LPG 83M74 No Change 83M74 56M04 83M75 60M35Pressure switch is factory set. No adjustment necessary. All models use the factory installed pressure switch from 0−4500 feet (0−1370 m).V−TYPICAL OPERATING CHARACTERISTICSA−Blower Operation and AdjustmentNOTE− The following is a generalized procedure anddoes not apply to all thermostat controls.1 − Blower operation is dependent on thermostat controlsystem.2 − Generally, blower operation is set at thermostat subbasefan switch. With fan switch in ON position, bloweroperates continuously. With fan switch in AUTO position,blower cycles with demand or runs continuously whileheating or cooling circuit cycles.3 − In all cases, blower and entire unit will be off when thesystem switch is in OFF position.B−Temperature RiseTemperature rise for G43UF units depends on unit input,blower speed, blower horsepower, filter resistance andinstalled duct system resistance. The blower speed mustbe set for unit operation within the range of TEMPERA-TURE RISE °F" listed on the unit rating plate.To Measure Temperature Rise:1− Place plenum thermometers in the supply and return airplenums. Locate supply air thermometer in the first horizontalrun of the plenum where it will not pick up radiantheat from the heat exchanger.2 − Set thermostat to highest setting.3 − After plenum thermometers have reached their highestand steadiest readings, subtract the two readings.The difference should be in the range listed on the unitrating plate. If the temperature is too low, decreaseblower speed. If temperature is too high, first check thefiring rate. Provided the firing rate is acceptable, increaseblower speed to reduce temperature. Tochange blower speed taps see the Blower Speed Tapssection in this manual.Page 36