Carrier NDK33BN0KB, Operation & Service Manual

Page: 128 / 270

62-61753-21 7-12
Alarm
NO.
Steps ALARM / CAUSE CORRECTIVE ACTION
18 LOW REFRIGERANT PRESSURE

TRIGGER-ON:
Suction Pressure has been less than -0.43 bar (-6.3 psig) for the Low Suction Pressure Configuration
time or 10 seconds (whichever is less).

UNIT CONTROL: Engine Operation: Engine and unit shutdown and alarm.
Standby operation: alarm only or (if configured for shutdown) refrigeration
system shutdown and alarm with PSCON still energized.

RESET CONDITION: Auto Reset when suction pressure rises above 0.0 (bar or psig). Alarm may be
manually reset via keypad or by turning the unit OFF, then ON again.
NOTE: Follow the steps below until a problem is found. Once a repair or correction has been made, the active
alarm should clear itself (refer to reset condition above). Operate the unit through the appropriate modes to see if
any active alarm occurs. Continue with the steps below as necessary.
1 Check For Low Refrigerant Charge
a. Check refrigerant level in the re-
ceiver.
Generally, level should be between upper & lower sight
glasses with a refrigerated compartment temperature
of 1.0°C (35°F) or lower. refer to Section 8.5.4
2 Check System Pressures
a. Install Manifold Test Set and check
and compare compressor dis-
charge & suction pressures with
those shown on the microproces-
sor.
Suction pressure must be above 0.0 (psig or bar)
Suction & Discharge Pressures must have the same
reading on gauges & on microprocessor display.
NOTE: Microprocessor suction (CSP) and evaporator
(EVOP) pressure readings have a maximum value of
7.5 bar (100 psig) The actual suction pressure must be
lower than 100 psig in order to perform this test.
3
Manually Defrost Unit
a. Defrost unit and terminate auto-
matically.
Typical defrost cycle time is 5-20 minutes.
Suction pressure should rise gradually during cycle.
4 Check Transducer Wiring
a. Inspect transducer & connector
pins & terminals. (See wiring
schematic Section 10.)
No physical damage to sensor.
No damaged or corroded pins in plug.
b. Energize sensor circuit.
c. Check for voltage at the transducer
plug between pins A (+) and B
(ground).
Refer to Note 2 Page 7-2.
Voltage should be approximately 12 VDC.
If OK, go to step e. If not, continue with this step.
d. Reconnect the transducer plug.
Check for voltage between 1MP-
29 and ground.
Voltage should be greater than 0.24 VDC and less
than 5 VDC.
5 Perform Pretrip Check
a. Clear Active Alarm list, then run
Pretrip & check for alarms.
Any active alarms must be corrected and cleared be-
fore proceeding.
6 Check Unloader Operation
a. Check Unloader Solenoid Valve Refer to Alarm 112
Additional steps on the next page.