Carrier 48LC 24 - Page 39

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Table 16 – Humidi--MiZer System Service Analysis
PROBLEM CAUSE REMEDY
Subcooling Reheat Mode
Will Not Activate.
General cooling mode problem. See Cooling Service Analysis (Table 15).
No dehumidification demand. See No Dehumidification Demand, below.
IOB operation. See IOB Operation, below.
Circuit LDV valve problem. SeeLDVValveOperation,below.
Hot Gas Reheat Mode
Will Not Activate.
General cooling mode problem. See Cooling Service Analysis (Table 15).
No dehumidification demand. See No Dehumidification Demand, below.
IOB operation. See IOB Operation, below.
Circuit LDV valve problem. SeeLDV(3---Way)ValveOperation,below.
Circuit RDV valve is not open. SeeRDVValveOperation,below.
Outdoor temperature too low.
Check Reheat Circuit Limit Temperatures
Unit ConfigurationsCoolingHumz Lockout OAT
No Dehumidification Demand.
Relative humidity setpoint is
too low — Humidistat
Check/reduce setting on accessory humidistat.
Relative humidity setpoint is
too low — RH sensor.
Check Space RH Setpoints (SetpointsSPRH)
Software configuratio n error
for accessory humidistat.
Check Space Humidity Switch (SETTINGS  UNIT CONFIGURATIONS
 SWITCH INPUTS CONFIGS  HUMSTAT CHANNEL)
Software configuratio n error
for accessory humidity sensor.
Check RH Sensor (SETTINGS  UNIT CONFIGURATIONS  ANALOG
INPUTS CONFIGS  SPRH SENSOR CHANNEL)
No humidity signal. Check wiring. Check humidistat or humidity sensor.
IOB Operation.
Communication loss to Input--- Output Board.
Check wiring connections. Alert A099 --- COMM LOSS WITH SIOB
No power to output terminals. Check wiring.
Relay outputs do not change state. Replace faulty IOB.
L D V ( 3 --- W a y ) V a l v e O p e r a t i o n .
No 24V signal to input terminals.
Check using ServiceLIQ DIVERT A TEST
Check IOB relay output.
Check Wiring.
Check transformer and circuit beaker or fuses.
Solenoid coil burnout.
Check continuous over-voltage is less than 10%.
Check under-voltage is less t han 15%.
Check for missing coil assembly parts.
Check for damaged valve enclosing t ube.
Stuck valve. Replace valve. Replace filter drier.
RDV Valve Operation.
(NOTE: Normally Closed
When De-energized)
No 24V signal to input terminals.
Check using ServiceRDV A TEST
Check IOB relay output.
Check wiring.
Check transformer and circuit breaker or fuses.
Solenoid coil burnout.
Check continuous over-voltage is less than 10%.
Check under-voltage is less t han 15%.
Check for missing coil assembly parts.
Check for damaged valve enclosing t ube.
Stuck valve. Replace valve. Replace filter drier.
Low Sensible Capacity in Normal Cool
or Subcooling Reheat Modes.
RDV valve open or leaking. SeeRDVValveOperation,above.
Low Suction Pressure and High
Superheat During Normal Cool Mode.
General cooling mode problem. See Cooling Service Analysis (Table 15).
RDV valve open or leaking. SeeRDVValveOperation,above.
RDV Valve Cycling On/Off.
Hot Gas Reheat mode low suction pressure limit.
Normal Operation During Mixed Circuit Subcooling and Hot Gas Reheat
Modes at Lower Outdoor Temperatures.
LEGEND
IOB --- I n p u t --- Ou t p u t B o a r d
LDV --- L i q u i d D iv e r t e r Va l v e
RDV --- Reheat Discharge Valve
RH --- Relative Humidity