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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.
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.
Table 14 – Cooling Service Analysis
PROBLEM CAUSE REMEDY
Compressor and Fan Will Not
Start.
Power failure. Call power company.
Fuse blown or circuit breaker tripped. Check CB1,
CB2, and CB3.
Replace fuse or reset circuit breaker.
Disconnect off. Power disconnect.
Compressor time guard to prevent short cycling. Check using ComfortLink Scrolling Marquee.
Thermostat or occupancy schedule set point not
calling for Cooling.
Check using ComfortLink Scrolling Marquee.
Outdoor temperature too low. Check Compressor Lockout Temperature using
ComfortLink Scrolling Marquee.
Active alarm. Check active alarms using ComfortLink Scrolling
Marquee.
Compressor Cycles (other than
normally satisfying thermostat).
Insufficient line voltage. Determine cause and correct.
Active alarm. Check active alarms using ComfortLink Scrolling
Marquee.
Compressor Operates
Continuously.
Unit undersized for load. Decrease load or increase size of unit.
Thermostat or occupancy schedule set point too low. Reset thermostat or schedule set point.
Dirty air filters. Replace filters.
Low refrigerant charge. Check pressure, locate leak, repair, evacuate, and
recharge.
Condenser coil dirty or restricted. Clean coil or remove restriction.
Excessive Condenser Pressures.
Loose condenser thermistors. Tighten thermistors.
Dirty condenser coil. Clean coil.
Refrigerant overcharge. Recover excess refrigerant.
Faulty TXV. 1. Check TXV bulb mounting and secure tightly to
suction line and insulate.
2. Replace TXV (and filter drier) if stuck open or
closed.
Condenser air restricted or air short cycling. Determine cause and correct.
Restriction in liquid tube. Remove restriction.
Condenser Fans Not Operating. No Power to contactors. Fuse blown or plug at motor loose.
Excessive Suction Pressure.
High heat load. Check for sources and eliminate
Faulty TXV. 1. Check TXV bulb mounting and secure tightly to
suction line and insulate.
2. Replace TXV (and filter drier) if stuck open or
closed.
Refrigerant overcharged. Recover excess refrigerant.
Suction Pressure Too Low.
Dirty air filters. Replace air filters.
Low refrigerant charge. Check pressure, locate leak, repair, evacuate, and
recharge.
Faulty TXV. 1. Check TXV bulb mounting and secure tightly to
suction line and insulate.
2. Replace TXV (and filter drier) if stuck open or
closed.
Insufficient evaporator airflow. Check belt tension. Check for other restrictions.
Temperature too low in conditioned area (low
return‐air temperature).
Reset thermostat or occupancy schedule.
LEGEND
CB - Circuit Breaker
TXV - Thermostatic Expansion Valve
48/50PG and PM