Carrier 48VT(N) - Manual (Page 35)

35
Table 11 – Troubleshooting Guide -- Cooling or Heat Pump Heating Mode
SYMPTOM CAUSE REMEDY
Compressor and Outdoor 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 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 Outdoor
fan runs.
Faulty wiring or loose connections in compressor circuit Check wiring and repair or replace.
Compressor motor burned out, seized, or internal over-
load open
Determine cause Replace compressor.
Defective run/start capacitor, overload, start relay Determine cause and replace.
One leg of 3---phase power dead
Replace fuse or reset circuit breaker. Determine
cause.
Three---phase scroll compressor makes
excessive noise, and there may
be a low pressure differential.
Scroll compressor is rotating in the wrong direction
Correct the direction of rotation by reversing the
3---phase power leads to the unit.
Compressor cycles (other than normally
satisfying thermostat).
Refrigerant overcharge or undercharge
Recover refrigerant, evacuate system, and recharge
to capacities shown on nameplate.
Defective compressor Replace and determine cause.
Insufficient line voltage Determine cause and correct.
Blocked Outdoor Determine cause and correct.
Defective run/start capacitor, overload or start relay Determine cause and replace.
Defective thermostat Replace thermostat.
Faulty Outdoor---fan motor or capacitor Replace.
Damaged reversing valve Determine cause and correct
Restriction in refrigerant system Locate restriction and remove.
Compressor operates continuously.
Dirty air filter Replace filter.
Unit undersized for load Decrease load or increase unit size.
Thermostat set too low Reset thermostat.
Low refrigerant charge Locate leak, repair, and recharge.
Mechanical damage in compressor. Replace compressor.
Air in system Recover refrigerant, evacuate system, and recharge.
Frosted coil with incorrect defrost operation
Check defrost time settings, Reset as necessary
Check defrost temperature switch, Replace as nec-
essary
Outdoor coil dirty or restricted Clean coil or remove restriction .
Excessive head pressure.
Dirty air filter Replace filter.
Dirty Indoor or Outdoor coil Clean coil.
Refrigerant overcharged Recover excess refrigerant.
Air in system Recover refrigerant, evacuate system, and recharge.
Indoor or Outdoor air restricted or air short---cycling Determine cause and correct.
Head pressure too low.
Low refrigerant charge Check for leaks, repair, and recharge.
Compressor IPR leaking Replace compressor.
Restriction in liquid tube Remove restriction.
Excessive suction pressure.
High heat load Check for source and eliminate.
Compressor IPR leaking Replace compressor.
Refrigerant overcharged Recover excess refrigerant.
Reversing valve hung up or leaking internally Replace valve
Suction pressure too low.
Dirty air filter Replace Filter.
Low refrigerant charge Check for leaks, repair, and recharge.
Metering device or low side restricted Remove source of restriction.
Insufficient Indoor airflow
Increase air quantity. Check filter — replace if neces-
sary.
Temperature too low in conditioned area Reset thermostat.
Outdoor ambient below 55°F (12.8°C) Install low---ambient kit.
Field---installed filter---drier restricted Replace.
(Heat) Outdoor coil frosted
Move timer on control board to 30 minutes between
defrost cycles
Compressor runs but outdoor fan does
not
NC (normally closed) contacts on defrost board open
Check condition of relay on board Replace if neces-
sary
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