Carrier 50TC*17 Series Service And Maintenance Instructions

16Table 4 – Humidi−MiZer TroubleshootingPROBLEM CAUSE REMEDYSubcooling Reheat Mode WillNot ActivateGeneral cooling mode problem See Cooling Service Troubleshooting (Table 4).No dehumidification demand See No Dehumidification Demand, below.CRC relay operation See CRC Relay Operation, below.Circuit RLV, CLV or LDV valve problem See CLV, RLV or LDV Valve Operation, below.Hot Gas Reheat Mode Will NotActivateGeneral cooling mode problem See Cooling Service Troubleshooting (Table 4).No dehumidification demand See No Dehumidification Demand, below.CRC relay operation See CRC Relay Operation, below.Circuit RLV, CLV or LDV valve problem See CLV, RLV or LDV Valve Operation, below.Circuit RDV valve is not open See RDV Valve Operation, below.Outdoor temperature too low Check Reheat 2 Circuit Limit Temperatures (Configuration → HMZR→ RA.LO and RB.LO) using ComfortLink Scrolling Marquee.No Dehumidification DemandRelative humidity setpoint too low — Humidistat Check/reduce setting on accessory humidistat.Relative humidity setpoint too low — RH sensor Check Space RH Setpoints (Setpoints → RH.SP and RH.UN) andoccupancy using ComfortLink Scrolling Marquee.Software configuration error for accessoryhumidistatCheck Space Humidity Switch (Configuration UNIT RH.SW) usingComfortLink Scrolling Marquee.Software configuration error for accessoryhumidity sensorCheck RH Sensor on OAQ Input (Configuration → UNIT → RH.S)using ComfortLink Scrolling Marquee.No humidity signal Check wiring. Check humidistat or humidity sensor.CRC Relay OperationNo 24V signal to input terminalsCheck using Cool→Reheat1 Valve Test (Service Test → HMZR →CRC) using ComfortLink Scrolling Marquee.Check MBB relay output.Check wiring.Check transformer and circuit breaker.No power to output terminals Check wiring.Relay outputs do not change state Replace faulty relay.RLV, CLV or LDV Valve OperationNo 24V signal to input terminalsCheck using Cool→Reheat1 Valve Test (Service Test → HMZR →CRC) using ComfortLink Scrolling Marquee.Check CRC Relay Operation.Check Wiring.Check transformer and circuit beaker or fuses.Solenoid coil burnoutCheck continuous over-voltage is less than 10%.Check under-voltage is less than 15%.Check for missing coil assembly parts.Check for damaged valve enclosing tube.Stuck valve Replace valve. Replace filter drier.RDV Valve Operation(NOTE: Normally Closed WhenDe-energized)No 24V signal to input terminalsCheck using Cool→Reheat1 Valve Test (Service Test → HMZR →RHV.A or RHV.B) using ComfortLink Scrolling Marquee.Check MBB relay output.Check wiring.Check transformer and circuit breaker or fuses.Solenoid coil burnoutCheck continuous over-voltage is less than 10%.Check under-voltage is less than 15%.Check for missing coil assembly parts.Check for damaged valve enclosing tube.Stuck valve Replace valve. Replace filter drier.Low Latent Capacity in Subcooling or Hot Gas Reheat Modes CLV valve open or leaking See CLV Valve Operation, above.Low Sensible Capacity in NormalCool or Subcooling ReheatModes RDV valve open or leaking See RDV Valve Operation, above.Low Suction Pressure and HighSuperheat During Normal CoolModeGeneral cooling mode problem See Cooling Service Troubleshooting (Table 4).RDV valve open or leaking See RDV Valve Operation, above.Low Suction Pressure and HighDischarge PressureGeneral cooling mode problem See Cooling Service Troubleshooting (Table 4).Both RLV and CLV valves closed See RLV and CLV Valve Operation, above.RDV Valve Cycling On/Off Hot Gas Reheat mode low suction pressure limit Normal Operation During Mixed Circuit Subcooling and Hot GasReheat Modes at Lower Outdoor Temperatures.Circuit B Will Not Operate WithCircuit A Off Normal operation. Motormaster outdoor fancontrol requires operation of circuit A. NoneLEGENDCRC — Cooling/Reheat ControlCLV — Cooling Liquid ValveRLV — Reheat Liquid ValveRH — Relative HumidityRDV — Reheat Discharge Valve