Carrier 48TC 04 Series, Service And Maintenance Instructions

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TROUBLESHOOTING COOLING SYSTEM
Refer to Table 5 for Troubleshooting Cooling System topics.
Table 5 – Cooling System Troubleshooting
PROBLEM CAUSE REMEDY
Compressor and
Condenser Fan Will Not
Start.
Power failure. Call power company.
Fuse blown or circuit breaker tripped. Replace fuse or reset circuit breaker.
Defective thermostat, contactor, transformer, or
control relay.
Replace defective component.
Insufficient line voltage. Determine cause and correct.
Incorrect or faulty wiring. Check wiring diagram and rewire correctly.
Thermostat setting too high. Lower thermostat setting below room temperature.
Compressor Will Not Start
But Condenser Fan Runs.
Faulty wiring or loose connections in compressor
circuit.
Check wiring and repair or replace. Tighten loose
connections.
Compressor motor burned out, seized, or
internal overload open.
Determine cause. Replace compressor.
Defective run/start capacitor, overload, start relay. Determine cause and replace defective component.
One leg of three---phase power dead.
Replace fuse or reset circuit breaker. Determine
cause.
Compressor Cycles (other
than normally satisfying
thermostat).
Refrigerant overcharge or undercharge.
Recover refrigerant, evacuate system, and recharge
to to values on nameplate.
Defective compressor. Replace defective compressor.
Insufficient line voltage. Determine cause and correct.
Blocked condenser. Determine cause and correct.
Defective run/start capacitor, overload, or start
relay.
Determine cause and replace.
Defective thermostat. Replace thermostat.
Faulty condenser---fan motor or capacitor. Replace defective fan motor or capacitor.
Restriction in refrigerant system. Locate restriction and remove.
Compressor Operates
Continuously.
Dirty air filter. Replace air filter.
Unit undersized for load. Decrease load or replace with larger unit.
Thermostat set too low. Reset thermostat.
Low refrigerant charge. Locate leak; repair and recharge.
Leaking valves in compressor. Replace compressor.
Air in system. Recover refrigerant, evacuate system, and recharge.
Condenser coil dirty or restricted. Clean coil or remove restriction.
Excessive Head Pressure.
Dirty air filter. Replace air filter.
Dirty condenser coil. Clean condenser coil.
Refrigerant overcharged. Recover excess refrigerant.
Faulty TXV valve.
1. Check TXV bulb mounting and secure tightly to
suction line and insulate.
2. Replace TXV valve and filter drier if stuck open
or closed.
Condenser air restricted or air short---cycling. Determine cause and correct.
Head Pressure Too Low.
Low refrigerant charge. Check for leaks; repair and recharge.
Compressor valves leaking. Replace compressor.
Restriction in liquid tube. Remove restriction.
Excessive Suction
Pressure.
High head load. Check for source and eliminate.
Compressor valves leaking. Replace compressor.
Refrigerant overcharged. Recover excess refrigerant.
Suction Pressure Too Low.
Dirty air filter. Replace air filter.
Low refrigerant charge. Check for refrigerant leaks; repair and recharge.
Faulty TXV valve.
1. Check TXV bulb mounting and secure tightly to
suction line and insulate.
2. Replace TXV valve and filter drier if stuck open
or closed.
Insufficient evaporator airflow.
Increase air quantity. Check filter and replace if
necessary. Check belt tension on blower.
Temperature too low in conditioned area. Reset thermostat.
Outdoor ambient below 25° F. Install low---ambient kit.
Evaporator Fan Will Not
Shut Off.
Time off delay not finished. Wait for 30---second off delay.
Compressor Makes
Excessive Noise.
Compressor rotating in wrong direction. Reverse the 3---phase power leads.
48TC