Carrier 69NT40-561-300, Operation And Service Manual

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5–9 T-365
3. TO RUN AN INDIVIDUAL TEST: Scroll through the selections by pressing the UP ARROW or DOWN
ARROW keys to display an individual test code. Pressing ENTER when the desired test code is displayed.
a. 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.
b. While the tests are being executed, the user may terminate the pre − trip diagnostics by pressing and
holding 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.
c. During Pre − trip testing, current limiting and pressure limiting are both active, except during P − 7 (High
Pressure Switch Testing) when pressure limiting is turned off.
4. Pre − Trip Test Results
At the end of the pre − trip test selection menu, the message “P,” “rSLts” (Pre − trip results) will be displayed.
Pressing the ENTER key will allow the user to see the results for all sub-tests (i.e., 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.
5.9 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 disagree-
ment 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). Normally,
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
invalidated. 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.