Carrier 50TC*17 Series Service And Maintenance Instructions page 16

PROBLEM
Subcooling Reheat Mode Will
Not Activate
Hot Gas Reheat Mode Will Not
Activate
No Dehumidification Demand
CRC Relay Operation
RLV, CLV or LDV Valve Operation
RDV Valve Operation
(NOTE: Normally Closed When
De-energized)
Low Latent Capacity in Subcool­
ing or Hot Gas Reheat Modes
Low Sensible Capacity in Normal
Cool or Subcooling Reheat
Modes
Low Suction Pressure and High
Superheat During Normal Cool
Mode
Low Suction Pressure and High
Discharge Pressure
RDV Valve Cycling On/Off
Circuit B Will Not Operate With
Circuit A Off
LEGEND
CRC — Cooling/Reheat Control
CLV — Cooling Liquid Valve
RLV — Reheat Liquid Valve
RH — Relative Humidity
RDV — Reheat Discharge Valve
Table 4 – Humidi−MiZerR Troubleshooting
CAUSE
General cooling mode problem
No dehumidification demand
CRC relay operation
Circuit RLV, CLV or LDV valve problem
General cooling mode problem
No dehumidification demand
CRC relay operation
Circuit RLV, CLV or LDV valve problem
Circuit RDV valve is not open
Outdoor temperature too low
Relative humidity setpoint too low — Humidistat
Relative humidity setpoint too low — RH sensor
Software configuration error for accessory
humidistat
Software configuration error for accessory
humidity sensor
No humidity signal
No 24V signal to input terminals
No power to output terminals
Relay outputs do not change state
No 24V signal to input terminals
Solenoid coil burnout
Stuck valve
No 24V signal to input terminals
Solenoid coil burnout
Stuck valve
CLV valve open or leaking
RDV valve open or leaking
General cooling mode problem
RDV valve open or leaking
General cooling mode problem
Both RLV and CLV valves closed
Hot Gas Reheat mode low suction pressure limit
Normal operation. Motormaster outdoor fan
control requires operation of circuit A.
See Cooling Service Troubleshooting (Table 4).
See No Dehumidification Demand, below.
See CRC Relay Operation, below.
See CLV, RLV or LDV Valve Operation, below.
See Cooling Service Troubleshooting (Table 4).
See No Dehumidification Demand, below.
See CRC Relay Operation, below.
See CLV, RLV or LDV Valve Operation, below.
See RDV Valve Operation, below.
Check Reheat 2 Circuit Limit Temperatures (Configuration → HMZR
→ RA.LO and RB.LO) using ComfortLink Scrolling Marquee.
Check/reduce setting on accessory humidistat.
Check Space RH Setpoints (Setpoints → RH.SP and RH.UN) and
occupancy using ComfortLink Scrolling Marquee.
Check Space Humidity Switch (Configuration UNIT RH.SW) using
ComfortLink Scrolling Marquee.
Check RH Sensor on OAQ Input (Configuration → UNIT → RH.S)
using ComfortLink Scrolling Marquee.
Check wiring. Check humidistat or humidity sensor.
Check using Cool→Reheat1 Valve Test (Service Test → HMZR →
CRC) using ComfortLink Scrolling Marquee.
Check MBB relay output.
Check wiring.
Check transformer and circuit breaker.
Check wiring.
Replace faulty relay.
Check 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.
Check 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.
Replace valve. Replace filter drier.
Check 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.
Check 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.
Replace valve. Replace filter drier.
See CLV Valve Operation, above.
See RDV Valve Operation, above.
See Cooling Service Troubleshooting (Table 4).
See RDV Valve Operation, above.
See Cooling Service Troubleshooting (Table 4).
See RLV and CLV Valve Operation, above.
Normal Operation During Mixed Circuit Subcooling and Hot Gas
Reheat Modes at Lower Outdoor Temperatures.
None
16
REMEDY