Cooling Troubleshooting - Carrier 48/50PG Series Controls, Start-Up, Operation, Service And Troubleshooting Instructions

Cooling Troubleshooting

Use the Scrolling Marquee display or a CCN device to view the
cooling status display and the cooling diagnostic display (see
Appendix A) for information on the cooling operation. Check the
current alarms and alarm history for any cooling alarm codes and
correct any causes. (See Table 12.) Verify any unique control
configurations per installed site requirements or accessories.
PROBLEM
Compressor and Fan Will Not
Start.
Compressor Cycles (other than
normally satisfying thermostat).
Compressor Operates
Continuously.
Excessive Condenser Pressures.
Condenser Fans Not Operating.
Excessive Suction Pressure.
Suction Pressure Too Low.
LEGEND
CB --- Circuit Breaker
TXV --- Thermostatic Expansion Valve
Table 14 – Cooling Service Analysis
CAUSE
Power failure.
Fuse blown or circuit breaker tripped. Check CB1,
CB2, and CB3.
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 TXV.
Condenser air restricted or air short cycling.
Restriction in liquid tube.
No Power to contactors.
High heat load.
Faulty TXV.
Refrigerant overcharged.
Dirty air filters.
Low refrigerant charge.
Faulty TXV.
Insufficient evaporator airflow.
Temperature too low in conditioned area (low
return-air temperature).
If alarms conditions are corrected and cleared, operation of the
compressors and fans may be verified by using the Service Test
mode. (See Table 4.) See Table 14 for general cooling service
analysis.
Call power company.
Replace fuse or reset circuit breaker.
Power disconnect.
Check using ComfortLink™ Scrolling Marquee.
Check using ComfortLink Scrolling Marquee.
Check Compressor Lockout Temperature using
ComfortLink Scrolling Marquee.
Check active alarms using ComfortLink Scrolling
Marquee.
Determine cause and correct.
Check active alarms using ComfortLink Scrolling
Marquee.
Decrease load or increase 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 TXV bulb mounting and secure tightly to
suction line and insulate.
2. Replace TXV (and filter drier) if stuck open or
closed.
Determine cause and correct.
Remove restriction.
Fuse blown or plug at motor loose.
Check for sources and eliminate
1. Check TXV bulb mounting and secure tightly to
suction line and insulate.
2. Replace TXV (and filter drier) if stuck open or
closed.
Recover excess refrigerant.
Replace air filters.
Check pressure, locate leak, repair, evacuate, and
recharge.
1. Check TXV bulb mounting and secure tightly to
suction line and insulate.
2. Replace TXV (and filter drier) if stuck open or
closed.
Check belt tension. Check for other restrictions.
Reset thermostat or occupancy schedule.
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REMEDY