101
Table 73 — Humidi-MiZer
®
Service Analysis
PROBLEM CAUSE REMEDY
Subcooling Mode Will Not
Activate
Circuit B compressors unavailable Check alarm history for general cooling mode operation problems.
See Table 72.
Check for Circuit B compressors locked out.
General Cooling Mode problem See Table 72.
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
IAQ
DEHU
D.SEN). See page 87.
Check for 24VDC from CEM (RARH, SPRH).
Check 4-20 mA signal from sensor.
Humidi-MiZer temperature sensors not
functioning - SAT, CCT
See "Thermistor Troubleshooting," see page 99.
No Dehumidification demand See “No Dehumidification Demand”, below.
3-way valve malfunction See “3-Way valve malfunction,” below.
Unit control software is not configured
for Humidi-MiZer system
Check that the unit is configured for Humidi-MiZer (Configura-
tion
IAQ
DEHU
D.SEL).
Reheat Mode Will Not Activate
Circuit B compressors unavailable Check alarm history for general cooling mode operation problems.
See Table 72.
Check for Circuit B 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
IAQ
DEHU
D.SEN). See page 87.
Check for 24 VDC from CEM (RARH, SPRH).
Check 4-20 mA signal 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
IAQ
DEHU
D.SEL).
No Dehumidification Demand
Relative Humidity set point is too low -
discrete input (Humidistat, Thermidi-
stat, etc.)
Check/reduce setting on discrete humidity input device.
Relative Humidity set point is too low -
RH sensor
Check the dehumidification relative humidity trip point (Configura-
tion
IAQ
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
IAQ
DEHU
D.SEN).
D.SEN = 1: RARH, 2:SPRH, 3: Discrete Input. See page 87.
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
Humid-MiZer Vent Reheat Set Point is
too low
Check the Vent Reheat Set Point Selection (Configuration
IAQ
DEHU
D.V.CF) and Vent Reheat Setpoint (Configura-
tion
IAQ
DEHU
D.V.HT). If used, check the Vent Reheat
RAT Offset also (Configuration
IAQ
DEHU
D.V.RA). See
page 87 for Humid-Mizer controls set-up.
Evaporator discharge temperature
(CCT) or supply air temperature (SAT)
thermistor is reading incorrectly.
See "Thermistor Troubleshooting,” page 99.
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
condenser 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
current 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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