Carrier Transicold 69NT40-561-001 Operation And Service Manual page 76

Alarm Code Cause
AL19 Discharge temperature
Discharge exceeds 135°C
Temperature (275°F) for 10 minutes
High within the last hour.
AL20
Control power fuse
Control (F3A or F3B) is open.
Contactor Fuse
(F3)
AL21
One of the 18 VAC
Control Circuit controller fuses (F1/F2)
Fuse (F1/F2) is open. Refer to Cd08.
AL22 Evaporator motor inter-
Evaporator IP nal protector (IP) is
open.
AL23 Controller fails to de-
Loss of Phase B tect current draw.
AL24 Compressor internal
Compressor IP protector (IP) is open.
T-340
Table 4–6 Controller Alarm Indications
Components
Restrictions in the
refrigeration sys-
tem.
Non-condens-
ables in the refrig-
eration system.
Additional Alarms
such as AL16,
AL24.
Check F3A, if the
fuse is open:
Check F3B, if the
fuse is open:
Check Voltage at
QC1:
System Sensors
Wiring
Controller
Evaporator Motor Shut down unit, discon-
Incoming Power
Compressor
4–40
Troubleshooting
Ensure the Discharge
Service Valve is fully
open.
Check the unit for air
flow restrictions.
With the unit off allow
system to stabilize to
ambient temperature.
Check system pressure
against PT Chart for
Table 7–5.
134a, refer to
Check compressor
operation.
Check PA, PB, CH coils
for short to ground, if
short is found:
Check ESV coil resis-
tance at TP7 to TP9, if
short to ground, or if re-
sistance is less than 4
ohms, coil is defective.
Check CF, ES, EF, HR
coils for short to ground,
if short is found, coil is
defective.
If voltage is present, it in-
dicates a defective mi-
croprocessor.
Check system sensors
for short to ground.
Check wiring for short to
ground.
Controller may have an
internal short.
nect power, & check
Evaporator Motor IP at
plug connection pins 4 &
6.
Check incoming power
source.
Shut down unit discon-
nect power, & check re-
sistance of compressor
windings at contactor
T1-T2, T2-T3.
Corrective Actions
Open the Discharge Ser-
vice Valve as needed.
Clean or remove any de-
bris from coils.
Correct as required, re-
fer to Refrigerant Charge
Section 7.7.1.
If the alarm persists, it
may indicate a failing
compressor, replace the
compressor, refer to
COMPRESSOR Ser-
vice Section 7.8.
Replace the defective
coil.
Replace the fuse.
Replace the defective
coil.
Replace the fuse.
Refer to Controller Ser-
vice Section 7.23.
Replace defective sen-
sor(s).
Repair as needed.
Replace controller, refer
to Controller Service
Section 7.23.
Replace defective evap-
orator fan motor, refer to
EVAPORATOR FAN
Sec-
MOTOR Service
tion 7.15.
Correct power source as
required.
Monitor unit, if alarm re-
mains active or is repeti-
tive replace the
compressor at the next
available opportunity, re-
fer to COMPRESSOR
Service Section 7.8.