Carrier 48GC04 Service And Maintenance Instructions

42ECONOMI$ER IV CONTROL MODESDetermine the EconoMi$er IV control mode before set up ofthe control. Some modes of operation may require differentsensors. The EconoMi$er IV is supplied from the factory witha supply-air temperature sensor and an outdoor-air temperaturesensor. This allows for operation of the EconoMi$er IV withoutdoor air dry bulb changeover control. Additional accesso-ries can be added to allow for different types of changeovercontrol and operation of the EconoMi$er IV and unit.Outdoor Dry Bulb ChangeoverThe standard controller is shipped from the factory configuredfor outdoor dry bulb changeover control. For this controlmode, the outdoor temperature is compared to a selectable setpoint on the OAT sensor. If the outdoor air temperature isabove the set point, the EconoMi$er IV will adjust the outdoorair dampers to minimum position. If the outdoor air tempera-ture is below the set point, the position of the outdoor airdampers will be controlled to provide free cooling using out-door air. When in this mode, the Free Cool LED next to theoutdoor enthalpy set point (ABCD) potentiometer will be on.The changeover temperature set point is controlled by the dipswitches on the sensor. See Fig. 69 for the switch positions cor-responding to the temperature changeover values. The ABCDpotentiometer on the controller should be turned fully clock-wise (CW) to the “D” position. See Fig. 70 for damper leakage.Fig. 69 — Outdoor Air TemperatureChangeover Set PointsOutdoor Enthalpy ChangeoverFor enthalpy control, accessory enthalpy sensor(P/N: HH57AC078) is required. Replace the standard outdoordry bulb temperature sensor with the accessory enthalpy sensorin the same mounting location. See Fig. 71. When the outdoorair enthalpy rises above the outdoor enthalpy changeover setpoint, the outdoor-air damper moves to its minimum position.The outdoor enthalpy changeover set point is set with the out-door enthalpy set point potentiometer on the EconoMi$er ® IVcontroller. The set points are A, B, C, and D. See Fig. 72 and73. The factory-installed 620-ohm jumper must be in placeacross terminals SR and SR+ on the EconoMi$er IV controller.Differential Enthalpy ControlFor differential enthalpy control, the EconoMi$er IV controlleruses two enthalpy sensors (HH57AC078 and CRENT-DIF004A00), one in the outside air and one in the return airduct. The EconoMi$er IV controller compares the outdoor airenthalpy to the return air enthalpy to determine EconoMi$er IVuse. The controller selects the lower enthalpy air (return or out-door) for cooling. For example, when the outdoor air has alower enthalpy than the return air, the EconoMi$er IV opens tobring in outdoor air for free cooling.Replace the standard outside air dry bulb temperature sensorwith the accessory enthalpy sensor in the same mounting loca-tion. See Fig. 62 on page 38. Mount the return air enthalpy sen-sor in the return air duct. See Fig. 71. Wiring is provided in theEconoMi$er IV wiring harness. See Fig. 66 on page 40. Theoutdoor enthalpy changeover set point is set with the outdoorenthalpy set point potentiometer on the EconoMi$er IV con-troller. When using this mode of changeover control, turn theenthalpy set point potentiometer fully clockwise to the Dsetting. See Fig. 72 and 73.Table 15 — Supply Air SensorTemperature/Resistance ValuesTEMPERATURE (F) RESISTANCE (ohms)-58 220,250-40 100,000-22 53,010-4 29,09114 16,50032 9,79550 5,97068 3,74777 3,00086 2,416104 1,597122 1,080140 746158 525176 376185 321194 274212 203230 153248 116257 102266 89284 70302 551 2 3ONOFF1 2 3ONOFF1 2 3ONOFF1 2 3ONOFF1 2 3ONOFF1 2 3ONOFF1 2 3ONOFF1 2 3ONOFF48°F53°F55°F58°F63°F68°F73°F78°FDIP SWITCHPOSITIONCHANGEOVERTEMPERATURE