Carrier 48LC Series Controls, Start-Up, Operation And Troubleshooting page 42

PROBLEM
Subcooling Reheat Mode
Will Not Activate
Hot Gas Reheat Mode
Will Not Activate
No Dehumidification Demand
IOB Operation
LDV (3-Way) Valve Operation
RDV Valve Operation.
(NOTE: Normally Closed
When De-energized)
Low Sensible Capacity in Normal Cool
or Subcooling Reheat Modes
Low Suction Pressure and High
Superheat During Normal Cool Mode
RDV Valve Cycling On/Off
LEGEND
IOB — Input-Output Board
LDV — Liquid Diverter Valve
RDV — Reheat Discharge Valve
RH — Relative Humidity
Table 19 — Humidi-MiZer System Service Analysis
CAUSE
General cooling mode problem.
No dehumidification demand.
IOB operation.
Circuit LDV valve problem.
General cooling mode problem.
No dehumidification demand.
IOB operation.
Circuit LDV valve problem.
Circuit RDV valve is not open.
Outdoor temperature too low.
Relative humidity setpoint is too low —
Humidistat
Relative humidity setpoint is too low — RH
sensor.
Software configuration error for accessory
humidistat.
Software configuration error for accessory
humidity sensor.
No humidity signal.
Communication loss to Input-Output Board.
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.
RDV valve open or leaking.
General cooling mode problem.
RDV valve open or leaking.
Hot Gas Reheat mode low suction pressure limit.
See Cooling Service Analysis (Table 18).
See No Dehumidification Demand, below.
See IOB Operation, below.
See LDV Valve Operation, below.
See Cooling Service Analysis (Table 18).
See No Dehumidification Demand, below.
See IOB Operation, below.
See LDV (3-Way) Valve Operation, below.
See RDV Valve Operation, below.
Check Reheat Circuit Limit Temperatures Unit
Configurations  Cooling Humz Lockout OAT
Check/reduce setting on accessory humidistat.
Check Space RH Setpoints (Setpoints SPRH)
Check Space Humidity Switch (SETTINGS UNIT
CONFIGURATIONS  SWITCH INPUTS CONFIGS
HUMSTAT CHANNEL)
Check RH Sensor (SETTINGS UNIT
CONFIGURATIONS ANALOG INPUTS CONFIGS
SPRH SENSOR CHANNEL)
Check wiring. Check humidistat or humidity sensor.
Check wiring connections. Alert A099 - COMM LOSS
WITH SIOB.
Check wiring.
Replace faulty IOB.
Check using Service LIQ DIVERT A TEST
Check IOB relay output.
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 Service RDV A TEST
Check IOB 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 RDV Valve Operation, above.
See Cooling Service Analysis (Table 18).
See RDV Valve Operation, above.
Normal Operation During Mixed Circuit Subcooling
and Hot Gas Reheat Modes at Lower Outdoor
Temperatures.
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REMEDY