82
Table 80 —
Humidi-MiZer
®
Service Analysis
(cont)
PROBLEM
CAUSE
REMEDY
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 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 page 70 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 79.
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 condi-
tions.
Check product data tables or ECAT for rated capacity at current
entering air and outdoor conditions.
Unit Initiates a Humidi-MiZer
Dehumidification Mode, but
Supply Air Temperature is
Overheating/Overcooling the
Space
Supply air setpoint for cooling is too
high/low
Check the unit supply air setpoint for cooling operation. This is the
temperature that humidimizer valves will modulate to meet during a
dehumidification mode.
Evaporator discharge temperature (CCT)
or supply air temperature (SAT)
thermistor is reading incorrectly.
See Thermistor Troubleshooting section on page 79.
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
See " Modulating Valves Not Functioning Properly"
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 condi-
tions.
Check product data tables or ECAT for rated capacity at current
entering air and outdoor conditions.
Low Sensible Capacity in Normal
Cooling Mode
Valve controlling gas bypass around the
condenser is stuck in an open position
or leaking
See " Modulating Valves Not Functioning Properly"
Valve controlling refrigerant flow to the
condenser is stuck in a partial open
position
See " Modulating Valves Not Functioning Properly"
General cooling mode problem
See Table 79.
Modulating Valves Not
Functioning Properly
Faulty wire connections
Check that the valve wiring is properly connected from the valve,
entering the control box and at the EXV board
EXV board malfunction
Check alarm history for A169 (Expansion Valve Control Board
Comm Failure)
Valve is stuck open/closed
Use Service Test to manually manipulate the valve position and
confirm supply air temperature changes during operation.
Run valve calibration through Service Test
Check valve motor for open or short circuited windings. Shut down
power to the unit and connect ohmmeter probes across the black
and white terminals. Resistance should measure 75 Ohms ±10%.
Next, connect ohmmeter probes across the red and green termi-
nals. Resistance should measure 75 Ohms ±10%. The meter
should not show an " open" or a " short" when a winding leg is mea-
sured. If either occurs, replace the valve.
Valve is not calibrated properly
Run valve calibration through Service Test.
Summary of Contents for Carrier Weathermaker 48A2
Page 105: ...105 Fig 20 Typical Main Control Box Wiring Schematic 48 50A2 A3 A4 A5 Units...
Page 106: ...106 Fig 21 Typical Auxiliary Control Box Wiring Schematic...
Page 107: ...107 Fig 22 Typical 2 Stage Gas Heat Wiring Schematic Size 060 Units Shown a48 8357...
Page 108: ...108 TO NEXT PAGE Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown A48 7296...
Page 109: ...109 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown cont A48 8358...
Page 110: ...110 Fig 24 Typical Electric Heat Control Schematic 50 Series Size 060 Units Shown a50 8228...
Page 111: ...111 Fig 25 Typical Power Schematic 48 50A2 A3 A4 A5 060 Unit Shown...
Page 112: ...112 Fig 26 Typical Low Ambient Controls Option Wiring...
Page 113: ...113 Fig 27 Typical Small Chassis Component Location Size 020 035 Units...
Page 114: ...114 Fig 28 Typical Large Chassis Component Locations Size 040 060 Units...
Page 118: ...118 Fig 30 Economizer Control Board ECB1 and VAV Control Board ECB2 A48 7706...
Page 142: ...142 A48 3733 Fig 56 Main Burner Removal...
Page 176: ...176 APPENDIX C VFD INFORMATION cont Fig F Internal Enclosure Fan Replacement A48 7716...
