Cooling Troubleshooting - Carrier 48HC 04-28 Controls, Start-Up, Operation And Troubleshooting

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 14.) Verify any
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.
Compressor not running but ComfortLink
Status show it is on.
LEGEND
TXV — Thermostatic Expansion Valve
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 6.) See Table 16 for general cooling service
analysis.
Table 16 — Cooling Service Analysis
CAUSE
Power failure.
Fuse blown or circuit breaker tripped.
Disconnect off.
Compressor time guard to prevent short cycling. Check using ComfortLink scrolling marquee.
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).
Condensate overflow switch, High pressure, or
Freeze protection thermostat has tripped.
50
REMEDY
Call power company.
Replace fuse or reset circuit breaker.
Power disconnect.
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.
Check Alarms. (T051 or T055), check switches
and conditions that can cause their trips.