Carrier WeatherMaster Puron 48HC D17, Service And Maintenance Instructions, Page: 14 / 100

14
LEGEND 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 ® or R-22 refrigerant. Use
only factory authorized TXVs. See Fig. 19.
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

RH.SP and
RH.UN) and occupancy using ComfortLink Scrolling
Marquee.
Software configuration error for accessory
humidistat.
Check Space Humidity Switch
(Configuration

UNIT

RH.SW) using ComfortLink
Scrolling Marquee.
Software configuration error for accessory
humidity sensor.
Check 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 Operation.
No 24V signal to input terminals.
Check using Cool

Reheat1 Valve Test (Service
Test

HMZR

CRC) using Comfort Link 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 Operation
No 24V signal to input terminals.
Check using Cool

Reheat1 Valve Test (Service
Test

HMZR

CRC) using Comfort Link Scrolling
Marquee.
Check CRC Relay Operation.
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 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 When
De-energized)
No 24V signal to input terminals.
Check using Cool

Reheat1 Valve Test (Service
Test

HMZR

RHV.A or RHV.B) using Comfort Link
Scrolling Marquee.
Check MBB 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 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 Normal
Cool or Subcooling Reheat Modes.
RDV valve open or leaking. See RDV Valve Operation, above
Low Suction Pressure and High
Superheat During Normal Cool Mode.
General cooling mode problem. See Cooling Service Troubleshooting (Table 5)
RDV valve open or leaking. See RDV Valve Operation, above
Low Suction Pressure and High
Discharge Pressure.
General cooling mode problem. See Cooling Service Troubleshooting (Table 5)
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 Gas Reheat Modes at Lower Outdoor Temperatures.
Circuit B Will Not Operate With
Circuit A Off.
Normal operation. Motormaster outdoor fan
control requires operation of circuit A.
None
Table 4 — Humidi-MiZer ® Troubleshooting (cont)
PROBLEM CAUSE REMEDY
CRC — Cooling/Reheat Control
CLV — Cooling Li q uid Valve
RDV — Reheat Discharge Valve
RH — Relative Humidity
RLV — Reheat Li q uid Valve