Carrier WeatherExpert 48N2 Controls, Start-Up, Operation, Service, And Troubleshooting page 104

PROBLEM
Compressor and Fan Will Not Start
Compressor Cycles (Other Than
Normally Satisfying Thermostat)
Compressor Operates
Continuously
Excessive Head Pressures
Condenser Fans Not Operating
Excessive Suction Pressure
Suction Pressure Too Low
LEGEND
EXV — Expansion Valve Control Board
ST — Suction Temperature
Table 72 — Cooling Service Analysis
CAUSE
Power failure.
Fuse blown or circuit breaker tripped. Check fuses and
circuit breakers in power and control panels.
Disconnect off.
Compressor time guard to prevent short cycling.
Thermostat or occupancy schedule set point not
calling for Cooling.
Outdoor temperature too low.
Active alarm.
Insufficient line voltage.
Active alarm.
Unit undersized for load.
Thermostat or occupancy schedule set point too low.
Dirty air filters.
Low refrigerant charge.
Condenser coil dirty or restricted.
Loose condenser thermistors.
Dirty condenser coil.
Refrigerant overcharge.
Faulty EXV.
EXV board malfunction.
Condenser air restricted or air short cycling.
Restriction in liquid tube.
No power to contactors.
High heat load.
Faulty EXV.
EXV board malfunction.
Refrigerant overcharged.
Dirty air filters.
Low refrigerant charge.
Faulty EXV.
EXV board malfunction.
Insufficient evaporator airflow.
Temperature too low in conditioned area (low return-
air temperature).
Check power source. Call power company.
Replace fuse or reset circuit breaker.
Power disconnect.
Check using ComfortLink Navigator display.
Check using ComfortLink Navigator display.
Check Compressor Lockout Temperature (MC.LO)
using ComfortLink Navigator display.
Check active alarms using ComfortLink Navigator
display.
Determine cause and correct.
Check active alarms using ComfortLink Navigator
display.
Decrease load or increase of size of unit.
Reset thermostat or schedule set point.
Replace filters.
Check pressure, locate leak, repair evacuate, and
recharge.
Clean coil or remove restriction.
Tighten thermistors.
Clean coil.
Recover excess refrigerant.
1. Check ST thermistor mounting and secure tightly
to suction line and insulate.
2. Replace EXV (and filter drier) if stuck open or
closed.
3. Run EXV auto-component test.
Check alarm history for A169 (expansion valve control
board comm. failure).
Determine cause and correct.
Remove restriction.
Fuse blown or plug at motor loose.
Check for sources and eliminate
1. Check ST thermistor mounting and secure tightly
to suction line and insulate.
2. Replace EXV (and filter drier) if stuck open or
closed.
3. Run EXV auto-component test.
Check alarm history for A169 (expansion valve control
board comm. failure).
Recover excess refrigerant.
Replace air filters.
Check for leaks, repair, and recharge.
1. Check ST thermistor mounting and secure tightly
to suction line and insulate.
2. Replace EXV (and filter drier) if stuck open or
closed.
3. Run EXV auto-component test.
Check alarm history for A169 (expansion valve control
board comm. failure).
Check belt tension. Check for other restrictions.
Reset thermostat or occupancy schedule.
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REMEDY