![background image](http://html1.mh-extra.com/html/carrier/transicold-69nt40-561-001/transicold-69nt40-561-001_operation-and-service-manual_2563859102.webp)
T-340
5–10
• Individually selected tests, other than the LED / Display test, will perform the operations necessary to ver
-
ify the operation of the component. At the conclusion, “PASS” or “FAIL” will be displayed. This message
will remain displayed for up to three minutes, during which time a user may select another test. If the
three minute time period expires, the unit will terminate pre-trip and return to control mode operation.
• While the tests are being executed, the user may terminate the pre-trip diagnostics by pressing and hold
-
ing the PRE-TRIP key. The unit will then resume normal operation. If the user decides to terminate a test
but remain at the test selection menu, the user may press the Up Arrow key. When this is done, all test
outputs will be de-energized and the test selection menu will be displayed.
• Throughout the duration of any Pre-trip test (except during P-7 high pressure switch tests) the current
limiting and pressure limiting are both active. The current limiting process is only active for P-7.
5.9.3
Displaying Pre-Trip Test Results
1. Press the PRE-TRIP key to access the Pre-trip test selection menu. “SELCt Prtrp” will be displayed.
2. Press the Arrow keys until the message “P,” “rSLts” (Pre-trip results) is displayed.
3. Press the ENTER key. The results for all Pre-trip sub tests are available from this menu (1-0, 1-1, etc).
The results will be displayed as “PASS” or “FAIL” for all the tests run to completion since power up. If a
test has not been run since power up, “- - - - -” will be displayed.
Once all Pre-test activity is completed, dehumidification and bulb mode must be reactivated manually if
required.
5.10 Probe Diagnostics
A complete temperature probe check is performed during the P5 Pre-trip test. A probe check is also run at the end
of a defrost cycle; the defrost light will remain on during this period. If supply probes are within limits and return
probes are within limits, the unit will return to normal operation. During normal operation, the controller continu
-
ously monitors and compares adjacent temperature probe readings.
The probe check procedure consists of running the evaporator fans for up to eight minutes in order to compare the
readings from the adjacent temperature probes. If a significant difference in temperature readings is detected
between probes, a defrost cycle, followed by another probe check may be initiated. Any continued disagreement
between probes will prompt the controller to invalidate the failed temperature probe, and the backup probe will be
used for temperature control.
In Perishable Mode, both pairs of supply and return probes are monitored for probe disagreement. Probe disagreement
is considered a difference of 0.5°C (0.9°F) or greater between the supply air sensors and/ or a difference of 2.0°C
(3.6°F) between the return air sensors. Probe disagreement found in either pair can trigger a defrost probe check.
In Frozen Mode, only the controlling probes are considered. Disagreement of the controlling probes can trigger a
defrost probe check, which will occur when the difference between the sensors is greater than 2.0°C (3.6°F). Nor
-
mally, the controlling probes are the return probes but if both return probes are invalidated, the supply probes are
used for control purposes. Probe disagreement of the non- controlling probe pair will not trigger a defrost probe
check.
If after the defrost probe check the supply probes agree and return probes agree, all supply and return sensors are
considered valid and the unit returns to normal control.
In the Case of Probe Disagreement:
If the supply probes disagree and the return probes agree, the controller will invalidate the worst supply probe. If the
probe check is run as part of Pre-trip P-5, an alarm will be triggered for the invalidated probe. If it is a run time defrost
probe check, the invalidated probe will be passed over and no alarm will be triggered. However, if the best supply
probe is greater than 1.2°C (2.2°F) difference with respect to its return probes, the best supply probe is also invali
-
dated. If unit is in Perishable Mode, a probe alarm will be triggered for both supply probes.
If the supply probes agree and the return probes disagree, invalidate the worst return probe. If the probe check is
being run as part of Pre-trip P-5, an alarm will be triggered for the invalidated probe. If it is a run time defrost probe
check, the invalidated probe will be passed over and no alarm will be necessary. If the best return probe is greater
than 1.2°C (2.2°F) difference with respect to its supply probes, then the best return probe is also invalidated. If the
unit is in perishable mode, a probe alarm will be triggered for both return probes.