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Table 86 — 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 (MC.LO) 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.
Compressors Operate Continuously
Unit undersized for load. Decrease load or increase of 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 Head 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.
Condenser Fan slips on shaft. Tighten fan hub setscrews.
Motor overload open. Check overload rating. Check for fan blade obstruction.
Motor burned out. Replace motor.
VFDs not functioning. Verify the VFDs; replace if needed.
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 for leaks, repair, 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
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