Carrier 48TCA04---A12 Service And Maintenance Instructions

71EconomizerEconomizer ExistsThis point tells the controller if there is an economizerinstalled on the unit.Factory Default = NO if no economizerYES if there is an economizer installedEconomizer Minimum PositionThis defines the lowest economizer position when theindoor fan is running and the building is occupied.Factory Default = 20%Range = 0--100 %Economizer High OAT LockoutIf the outdoor air temperature rises above this value,economizer cooling will be disabled and dampers willreturn and stay at minimum position.Factory Default = 75_FRange = 55--80_FPower Exhaust SetptWhen the economizer damper position opens above thispoint the power exhaust operation will begin. When thedamper position falls 10% below the setpoint, the powerexhaust will shutdown.Factory Default = 50%Range = 20--90 %NOTE: This point is only used when Continuous OccExhaust = NOContinuous Occ ExhaustThis point tells the controller when to run the powerexhaust if equipped on the unit. If set to YES, the powerexhaust will be on all the time when in occupied modeand will be off when in unoccupied mode. If set to NO thepower exhaust will be controlled by the Power ExhaustSetpoint.Factory Default = NOIAQMax Differential CO 2 SetptIf the difference between indoor an outdoor air qualitybecomes greater then this value the damper position willstay at the IAQ Greatest Min Dmpr Pos. configurationpointFactory Default = 650 PPMRange = 300--950 PPMIAQ Greatest Min Dmpr Pos.This is the greatest minimum position the economizer willopen to while trying to control the indoor air quality, CO2differential.Factory Default = 50% openRange = 10--60% openClocksetThis submenu screen allows you to set the date and timemanually. The Daylight Savings Time (DST) can also bechanged here. The date and time is automatically set whenever software is downloaded. The clock is a 24 hour clockand not am/pm. The time should be verified (and maybechanged) according to unit location and time zone.Factory Default = Eastern Standard TimeUSERPWThis submenu screen allows you to change the userpassword to a four number password of choice. The Userpassword change screen is only accessible with theAdministrator Password (1111). The ADMIN passwordwill always override the user password.OPERATING SEQUENCESBase Unit ControlsCooling, Units Without EconomizerWhen thermostat calls for cooling, terminals G and Y1 areenergized. The indoor--fan contactor (IFC) andcompressor contactor are energized and indoor--fan motor,compressor, and outdoor fan starts. The outdoor fan motorruns continuously while unit is cooling.Heating, Units Without EconomizerWhen the thermostat calls for heating, terminal W1 isenergized. To prevent thermostat short--cycling, the unit islocked into the Heating mode for at least 1 minute whenW1 is energized. The induced--draft motor is energizedand the burner ignition sequence begins. The indoor(evaporator) fan motor (IFM) is energized 45 secondsafter a flame is ignited. On units equipped for two stagesof heat, when additional heat is needed, W2 is energizedand the high--fire solenoid on the main gas valve (MGV)is energized. When the thermostat is satisfied and W1 isdeenergized, the IFM stops after a 45--second time offdelay.Cooling, Unit With EconoMi$er IVFor Occupied mode operation of EconoMi$er IV, theremust be a 24--v signal at terminals TR and N (providedthrough PL6--3 from the unit’s IFC coil). Removing thesignal at N places the EconoMi$er IV control inUnoccupied mode.During Occupied mode operation, indoor fan operationwill be accompanied by economizer dampers moving toMinimum Position setpoint for ventilation. If indoor fan isoff, dampers will close. During Unoccupied modeoperation, dampers will remain closed unless a Cooling(by free cooling) or DCV demand is received.Integrated EconoMi$er IV operation on 48TC singlecompressor model requires a 2--stage thermostat (Y1 andY2 switches).When free cooling using outside air is not available, theunit cooling sequence will be controlled directly by thespace thermostat as described above as Cooling, WithoutEconomizer. Outside air damper position will be closed orMinimum Position as determined by occupancy mode andfan signal.When free cooling is available as determined by theappropriate changeover command (dry bulb, outdoorenthalpy, differential dry bulb or differential enthalpy), acall for cooling (Y1 closes at the thermostat) will causethe economizer control to modulate the dampers open andclosed to maintain the unit supply air temperature at 50 to55_F. Compressor will not run.48TC