Carrier 50PG20-28 Controls, Start-Up, Operation, Service And Troubleshooting Instructions page 58

Table 44 -- Cooling Service Analysis
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
CAUSE
Power failure.
Fuse btown 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 calting for
Cooling
Outdoor temperature too tow.
REMEDY
Call power company
Replace fuse or reset circuit breaker.
Insufficient line voltage.
Active alarm.
Unit undersized for load
Thermostat or occupancy schedute set point too low.
Dirty air fitters.
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 fitters
Low refrigerant charge
Faulty TXV.
Insufficient evaporator airflow
Temperature too low in conditioned area (low return-air
temperature).
Power disconnect.
Check using ComfortLink
TM
Scrolling Marquee.
Check using ComfortLink ScroIling Marquee
Check Compressor Lockout Temperature using
ComfortLink ScroIling Marquee.
Active alarm. 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 coit or remove restriction.
Tighten thermistors.
CIean coil
Recover excess refrigerant
1 Check TXV bulb mounting and secure tightly to suction
tine 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
Iine and insulate.
2 Replace TXV (and filter drier) if stuck open or closed.
Recover excess refrigerant
Replace air fitters.
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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