Thermostatic Expansion Valve (Txv) - Carrier WeatherMaster Puron 48HC D17 Service And Maintenance Instructions

PROBLEM
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 Subcooling 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
RDV — Reheat Discharge Valve
RH — Relative Humidity
RLV — Reheat Liquid Valve
Table 4 — Humidi-MiZer
CAUSE
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. Check wiring.
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.
®
Troubleshooting (cont)
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 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 5)
See RDV Valve Operation, above
See Cooling Service Troubleshooting (Table 5)
See RLV and CLV Valve Operation, above
Normal Operation During Mixed Circuit Subcooling and
Hot Gas Reheat Modes at Lower Outdoor Temperatures.
None

THERMOSTATIC EXPANSION VALVE (TXV)

All 48HC units have factory-installed nonadjustable thermo-
static expansion valves (TXV). The TXVs are bleed port ex-
pansion valves with an external equalizer. TXVs are specifical-
ly designed to operate with Puron
only factory authorized TXVs. See Fig. 19.
14
REMEDY
® or R-22 refrigerant. Use