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106
Unit Initiates a Humidi-MiZer
Dehumidification Mode, but
Supply Air Temperature is
Overheating/Overcooling the
Space
Supply air set point for cooling is too
high/low
Check the unit supply air set point for cooling operation. This is the
temperature that the 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” on page 103.
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
conditions.
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 position less
than 100% open.
See “Modulating Valves Not Functioning Properly.”
General cooling mode problem
See Table 72.
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 terminals.
Resistance should measure 75 ohms ±10%. The meter should not
show an “open” or a “short” when a winding leg is measured. If either
occurs, replace the valve.
Valve is not calibrated properly.
Run valve calibration through Service Test.
Table 73 — Humidi-MiZer
®
Service Analysis (cont)
PROBLEM
CAUSE
REMEDY
Summary of Contents for WeatherExpert 48N2
Page 135: ...135 Fig 18 48 50N Typical Power Schematic Nominal 075 Ton Unit Shown ...
Page 136: ...136 Fig 19 48 50N Typical Power Schematic Nominal Ton 90 150 Units Shown ...
Page 137: ...137 Fig 20 48 50N Main Base Board Input Output Connections ...
Page 138: ...138 Fig 21 48 50N RXB EXB CEM Input Output Connections a48 9307 ...
Page 139: ...139 Fig 22 48 50N EXV SCB Input Output Connections a48 9308 ...
Page 140: ...140 Fig 23 48N Typical Modulating Gas Heat Unit Control Wiring ...
Page 141: ...141 Fig 24 50N Typical Electric Heat Unit Control Wiring ...
Page 144: ...144 Fig 27 48N Typical Gas Heat Section Wiring Nominal Ton 120 to 150 Units ...
Page 145: ...145 Fig 28 48 50N Typical Power Component Control Wiring 460 v ...
Page 146: ...146 Fig 29 48 50N Component Control Wiring 575 v Nominal Ton 075 to 150 Units ...
Page 147: ...147 Fig 30 48 50N Component Arrangement Power Box ...
Page 148: ...148 Fig 31 48 50N Component Arrangement Control Box ...
Page 240: ...240 APPENDIX D VFD INFORMATION CONT Fig G VFD Bypass Wiring Diagram WHEN USED ...