Carrier WeatherMaker 48A2020 Controls, Start-up, Operation, Service And Troubleshooting Instructions

110T414 (Damper Not Modulating)This alert occurs when the damper not modulating. The alert oc-curs when SAT does not change as expected when the damper ismoved. It is typically an indication that the damper has becomemechanically disconnected from the actuator. Investigate the ac-tuator and damper, and fix it. This alert resets automatically.T420 (R-W1 Jumper Must be Installed to Run Heat in Ser-vice Test)This alert occurs when a request for a heat output has occurredyet the W1 input is not high. A jumper must be installed be-tween R and W1 when trying to test heat in Service Test. Thealert will clear when Service Test is exited or if another ServiceTest mode is selected. Remove jumper when done using Ser-vice Test if the unit is operating with a thermostat. The jumpershould only be left in place if the unit is operating with a spacetemperature sensor.T421 (Thermostat Y2 Input On without Y1 On)This alert occurs in Thermostat Mode when Y2 is energizedand Y1 is not. Verify thermostat and thermostat wiring. WhenY2 turns on, the software will behave as if Y1 and Y2 are bothon. When Y2 turns off, the software will behave as if Y1 andY2 are both Off. This alert resets automatically when Y1 isturned on.T422 (Thermostat W2 Input On without W1 On)This alert occurs in Thermostat Mode when W2 is energizedand W1 is not. Verify thermostat and thermostat wiring. WhenW2 turns on, the software will behave as if W1 and W2 areboth on. When W2 turns off, the software will behave as if W1and W2 are both off. This alert resets automatically when W1is turned on.T423 (Thermostat Y and W Inputs On)This alert occurs in Thermostat Mode when Y1 or Y2 is ener-gized simultaneously with W1 or W2. Verify thermostat andthermostat wiring. The software will enter either the cooling orheating mode depending upon which input turned on first. Thisalert resets automatically when Y1 and Y2 are not on simulta-neously with W1 and W2.T424 (Thermostat G Input Off On a Cooling Call)This alert occurs in Thermostat Mode when the fan is not re-quested (G = ON) during cooling (Y1 or Y2 = ON). Verifythermostat and thermostat wiring.T500 (Current Sensor Board Failure – A1)T501 (Current Sensor Board Failure – A2)T502 (Current Sensor Board Failure – B1)T503 (Current Sensor Board Failure – B2)Alert codes 500, 501, 502, and 503 are for compressors A1,A2, B1, and B2 respectively. These alerts occur when the out-put of the current sensor (CS) is a constant high value. Thesealerts reset automatically. If the problem cannot be resolvedand the CS board must be replaced, the CS board can be tem-porarily disabled while securing a replaced board. A CS boardis disabled by setting Configuration  COOL  CS.A1,CS.A2, CS.B1 or CS.B2 to Disable.If the current sensor board malfunctions or is not properly con-nected to its assigned digital input, an alert will be generated. Ittakes 2 to 4 seconds to log the alert. If the alert is logged, itstays for a minimum of 15 seconds to provide the application areasonable time to catch the failure. Compressors will be notbe inhibited by this failure. Recovery is automatic. Reason forfailure may be a faulty current sensor board, incorrect wiring,or a damaged input on the MBB control board.A700 (Supply Air Temperature Sensor Failure)This alarm indicates a failure of the sensor supply air temperaturesensor or the leaving air temperature sensor (if using hydronicheat). This alarm occurs when the temperature sensor (Tempera-turesAIR.TSAT) is outside the range –40 to 240°F (–40 to116°C). This alarm resets automatically. The cause of the alarm isusually a faulty thermistor, a shorted or open thermistor caused bya wiring error, or a loose connection.T701 (Staged Gas 1 Thermistor Failure)T702 (Staged Gas 2 Thermistor Failure)T703 (Staged Gas 3 Thermistor Failure)If any of the staged gas thermistors (TemperaturesAIR.TS.G.L1-3) fails, an alert will be generated and the remainingthermistors will be averaged together (TemperaturesAIR.TS.G.LS) without the failed thermistor. Recovery is automat-ic. Reason for failure may be incorrect wiring, faulty thermis-tor, or a damaged input on the staged gas control board (SCB).A704 (Staged Gas Leaving Air Temperature Sum Total Failure)If all three staged gas thermistors (Temperatures  AIR.T S.G.L1-3) fail (the sensor is outside the range of –40°F to 240°F),staged gas will be shut down and this alarm will be generated. Re-covery is automatic. Reason for failure may be faulty wiring,faulty thermistors, or damaged inputs on the staged gas controlboard (SCB).T705 (Limit Switch Thermistor Failure)A failure (the sensor is outside the range of –40°F to 240°F) ofthis thermistor (TemperaturesAIR.TS.G.LM) will causean alert to occur and a disabling of the limit switch monitoringfunction for the staged gas control board (SCB). Recovery isautomatic. Reason for failure may be due to faulty wiring, afaulty thermistor, or a damaged input on the staged gas controlboard (SCB).A706 (Hydronic Evap Discharge Thermistor Failure)If the unit is configured for Humidi-MiZer, then the unit has athermistor (TemperaturesAIR.TCCT) installed betweenthe evaporator coil and the Humidi-MiZer coils that functions asthe evaporator discharge temperature thermistor for cooling. Ifthis thermistor fails, an alarm will be generated and the systemwill be shut down. Recovery is automatic. Reason for failuremay be due to faulty wiring, a faulty thermistor, or a damagedinput on the EXV control board.T707 (Digital Scroll Discharge Thermistor Failure)If the RXB control board is not receiving a signal from the dis-charge temperature thermistor, the alarm is generated. Thethermistor may be missing, disconnected, or a wire may bebroken. The alert will be generated and the digital scroll capac-ity will be locked at 50%. Reset is automatic.T800 (Cannot Enable MLV and Digital Scroll Simultaneously)MLV and Digital Scroll compressor cannot function together.When both options are enabled, an alert will occur.T802 (R22 Invalid for Design Series 4)For a unit with Design Series 4 model number, R-22 cannot bechosen as refrigerant type. When R-22 is configured in the re-frigerant type, an alert will occur warning the user to chooseR-410A as refrigerant.MAJOR SYSTEM COMPONENTSGeneralThe 48/50A Series package rooftop units with electric coolingand with gas heating (48A units) or electric cooling and elec-tric heating (50A units) contain the ComfortLink electroniccontrol system that monitors all operations of the rooftop. Thecontrol system is composed of several components as listed be-low. See Fig. 20-27 for typical control and power componentschematics. Figures 28 and 29 show the layout of the controlbox, unit, and thermistor and transducer locations.