Carrier WeatherExpert 48N2 Controls, Start-Up, Operation, Service, And Troubleshooting page 105

PROBLEM
Subcooling Mode Will Not
Activate
Reheat Mode Will Not Activate
No Dehumidification Demand
3-Way Valve Malfunction
Unit Initiates a Humidi-MiZer
Reheat Mode, but Supply Air
Temperature is Overheating/
Overcooling the Space
Table 73 — Humidi-MiZer
CAUSE
Circuit B compressors unavailable
General Cooling Mode problem
Humidi-MiZer relative humidity sensor
not functioning - RARH, SPRH, or field-
installed RH sensor
Humidi-MiZer temperature sensors not
functioning - SAT, CCT
No Dehumidification demand
3-way valve malfunction
Unit control software is not configured
for Humidi-MiZer system
Circuit B compressors unavailable
Humidi-MiZer relative humidity sensor
not functioning - RARH, SPRH, or field-
installed RH sensor
No Dehumidification demand
3-way valve malfunction
Unit control software is not configured
for Humidi-MiZer system
Relative Humidity set point is too low -
discrete input (Humidistat,
Thermidistat, etc.)
Relative Humidity set point is too low -
RH sensor
Software configuration error for the type
of relative humidity sensor being used
No humidity signal
No 24V signal to input terminals
Solenoid coil burnout
Stuck valve
Humid-MiZer Vent Reheat Set Point is
too low
Evaporator discharge temperature
(CCT) or supply air temperature (SAT)
thermistor is reading incorrectly.
Valve controlling gas bypass around
the condenser is not functioning
properly
Valve controlling refrigerant flow to the
condenser is not functioning properly
Modulating valves are not calibrated
properly
Unit control software indicates a
Humidi-MiZer Reheat Mode, but the
3-way valve is not functioning properly
Unit is not sized to meet the load at the
current entering air and outdoor
conditions
Service Analysis
®
Check alarm history for general cooling mode operation problems. See
Table 72.
Check for Circuit B compressors locked out.
See Table 72.
Check that a relative humidity sensor is connected and that the
appropriate sensor is configured in the unit software,
 
(Configuration DEHU
Check for 24VDC from CEM (RARH, SPRH).
Check 4-20 mA signal from sensor.
See "Thermistor Troubleshooting," page 103.
See "No Dehumidification Demand," below.
See "3-Way Valve Malfunction," below.
Check that the unit is configured for Humidi-MiZer system
 
(Configuration DEHU
Check alarm history for general cooling mode operation problems. See
Table 72.
Check for Circuit B compressors locked out.
Check that a relative humidity sensor is connected and that the
appropriate sensor is configured in the unit software,
 
(Configuration DEHU
Check for 24 VDC from CEM (RARH, SPRH).
Check 4-20 mA signal from sensor.
See "No Dehumidification Demand," below.
See "3-Way Valve Malfunction" below.
Check that the unit is configured for Humidi-MiZer system

(Configuration DEHU
Check/reduce setting on discrete humidity input device.
Check the dehumidification relative humidity trip point
 
(Configuration
DEHU
Check that the unit software is configured for the correct relative
humidity sensor (Configuration
RARH, 2:SPRH, 3: Discrete Input. See page 89.
Check wiring and sensor.
Check using Service Test mode.
Check wiring.
Check transformer and circuit breakers.
Check RCB relay output.
Check continuous over-voltage is less than 10%.
Check continuous under-voltage is less than 15%.
Check for missing coil assembly parts.
Replace solenoid coil.
Replace valve. Replace filter drier.
Check the Vent Reheat Set Point Selection (Configuration
 
DEHU D.V.CF) and Vent Reheat Setpoint
 
(Configuration DEHU
RAT Offset also (Configuration
Humid-MiZer controls set-up.
See "Thermistor Troubleshooting," page 103.
Check if SAT thermistor is in a location that is measuring stratified air.
See "Modulating Valves Not Functioning Properly."
See "Modulating Valves Not Functioning Properly."
Run valve calibration through Service Test.
See "3-Way Valve Malfunction."
Check product data tables or ECAT for rated capacity at current
entering air and outdoor conditions.
105
REMEDY
D.SEN). See page 89.
D.SEL).
D.SEN). See page 89.

D.SEL).
D.RH.S).
 
DEHU D.SEN). D.SEN = 1:
D.V.HT). If used, check the Vent Reheat
 
D.V.RA). See page 90 for
DEHU