87
Table 79 — Humidi-MiZer
®
Service Analysis
PROBLEM CAUSE REMEDY
Subcooling Mode Will Not
Activate
Circuit A compressors unavailable for 020-
027 units. Circuit B compressors unavail-
able for 030-060 units
Check alarm history for general cooling mode operation problems.
See Table 78.
Check for compressors locked out.
General Cooling Mode problem See Table 78.
Humidi-MiZer relative humidity sensor not
functioning - RARH, SPRH, or field
installed RH sensor
Check that a relative humidity sensor is connected and that the
appropriate sensor is configured in the unit software, (Configura-
tion
DEHU
D.SEN). See Table 69.
Check for 24VDC from CEM (RARH, SPRH).
Check 4 to 20 mA signals from sensor.
Humidi-MiZer temperature sensors not
functioning - SAT, CCT
See Thermistor Troubleshooting section on page 84.
No Dehumidification demand See “No Dehumidification Demand,” below.
3-way valve malfunction See “3-Way Valve Malfunction.”
Unit control software is not configured for
Humidi-MiZer system
Check that the unit is configured for Humidi-MiZer (Configuration
DEHU
D.SEL).
Reheat Mode Will Not Activate
Circuit A compressors unavailable for 020-
027 units. Circuit B compressors unavail-
able for 030-060 units
Check alarm history for general cooling mode operation problems.
See Table 78.
Check for compressors locked out.
Humidi-MiZer relative humidity sensor not
functioning - RARH, SPRH, or field
installed RH sensor
Check that a relative humidity sensor is connected and that the
appropriate sensor is configured in the unit software, (Configura-
tion
DEHU
D.SEN). See Table 69.
Check for 24 VDC from CEM (RARH, SPRH).
Check 4 to 20 mA signals from sensor.
No Dehumidification demand See “No Dehumidification Demand,” below.
3-way valve malfunction See “3-Way Valve Malfunction.”
Unit control software is not configured for
Humidi-MiZer system
Check that the unit is configured for Humidi-MiZer (Configuration
DEHU
D.SEL).
No Dehumidification Demand
Relative Humidity setpoint is too low - dis-
crete input (Humidistat, Thermidistat, etc.)
Check/reduce setting on discrete humidity input device.
Relative Humidity setpoint is too low - RH
sensor
Check the dehumidification relative humidity setpoint (Configura-
tion
DEHU
D.RH.S)
Software configuration error for the type of
relative humidity sensor being used
Check that the unit software is configured for the correct relative
humidity sensor (Configuration
DEHU
D.SEN). D.SEN = 1:
Return Air 2: Discrete Input. See page 74.
No humidity signal Check wiring and sensor.
3-Way Valve Malfunction
No 24V signal to input terminals Check using Service Test mode.
Check wiring.
Check transformer and circuit breakers.
Check RCB relay output.
Solenoid coil burnout 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.
Stuck valve Replace valve. Replace filter drier.
Unit Initiates a Humidi-MiZer
Reheat Mode, but Supply Air
Temperature is Overheating/
Overcooling the Space
Humidi-MiZer Vent Reheat Setpoint is too
low
Check the Vent Reheat Setpoint Selection (Configuration
DEHU
D.V.CF) and Vent Reheat Setpoint (Configuration
DEHU
D.V.HT). If used, check the Vent Reheat RAT Offset also
(Configuration
DEHU
D.V.RA). See Table 69 for Humidi-MiZer
controls set-up.
Evaporator discharge temperature (CCT)
or supply air temperature (SAT) thermistor
is reading incorrectly.
See Thermistor Troubleshooting section on page 84.
Check if SAT thermistor is in a location that is measuring stratified
air.
Valve controlling gas bypass around the
condenser is not functioning properly
See " Modulating Valves Not Functioning Properly"
Valve controlling refrigerant flow to the con-
denser is not functioning properly
See " Modulating Valves Not Functioning Properly"
Modulating valves are not calibrated properly Run valve calibration through Service Test.
Unit control software indicates a Humidi-
MiZer Reheat Mode, but the 3-way valve is
not functioning properly
See " 3-Way Valve Malfunction"
Unit is not sized to meet the load at the cur-
rent entering air and outdoor conditions.
Check product data tables or ECAT for rated capacity at current
entering air and outdoor conditions.
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