Carrier 48AJ Operating And Service Manual page 75

COMPRESSOR DOES NOT RUN
Active Alarm
Contactor Open
1. Power off.
2. Fuses blown in field power circuit.
3. No control power.
4. Compressor circuit breaker tripped.
5. Safety device lockout circuit active.
6. Low-pressure switch open.
7. High-pressure switch open.
8. Loose electrical connections.
9. Compressor stuck.
Contactor Closed
1. Compressor leads loose.
2. Motor windings open.
3. Single phasing.
COMPRESSOR STOPS ON HIGH PRESSURE
Outdoor Fan On
1. High-pressure switch faulty.
2. Airflow restricted.
3. Air recirculating.
4. Noncondensables in system.
5. Refrigerant overcharge.
6. Line voltage incorrect.
7. Refrigerant system restrictions.
Outdoor Fan Off
1. Fan slips on shaft.
2. Motor not running.
3. Motor bearings stuck.
4. Motor overload open.
5. Motor burned out.
COMPRESSOR CYCLES ON LOW PRESSURE
Indoor-Air Fan Running
1. Filter drier plugged.
2. Expansion valve power head defective.
3. Low refrigerant charge.
Airflow Restricted
1. Coil iced up.
2. Coil dirty.
3. Air filters dirty.
4. Dampers closed.
Indoor-Air Fan Stopped
1. Electrical connections loose.
2. Fan relay defective.
3. Motor overload open.
4. Motor defective.
5. Fan belt broken or slipping.
LEGEND
VFD — Variable Frequency Drive
Table 88 — Cooling Service Analysis
PROBLEM
Check active alarms using local display.
1. Restore power.
2. After finding cause and correcting, replace with correct size fuse.
3. Check secondary fuse(s); replace with correct type and size.
Replace transformer if primary windings receiving power.
4. Check for excessive compressor current draw. Reset breaker;
replace if defective.
5. Reset lockout circuit at circuit breaker.
6. Check for refrigerant undercharge, obstruction of indoor airflow, or
whether compressor suction shutoff valve is fully open. Make sure
liquid line solenoid valve(s) is open.
7. Check for refrigerant overcharge, obstruction of outdoor airflow, air
in system or whether compressor discharge valve is fully open. Be
sure outdoor fans are operating correctly.
8. Tighten all connections.
9. See compressor service literature.
1. Check connections.
2. See compressor service literature.
3. Check for blown fuse. Check for loose connection at compressor
terminal.
1. Replace switch.
2. Remove obstruction.
3. Clear airflow area.
4. Purge and recharge as required.
5. Purge as required.
6. Consult power company.
7. Check or replace filter drier, expansion valve, etc. Check that
compressor discharge valve is fully open.
1. Tighten fan hub setscrews.
2. Check power and capacitor.
3. Replace bearings.
4. Check overload rating. Check for fan blade obstruction.
5. Replace motor.
1. Replace filter drier.
2. Replace power head.
3. Add charge. Check low-pressure switch setting.
1. Check refrigerant charge.
2. Clean coil fins.
3. Clean or replace filters.
4. Check damper operation and position.
1. Tighten all connections.
2. Replace relay.
3. Power supply.
4. Replace motor.
5. Replace or tighten belt.
75
SOLUTION