T-364 4−4
CAUTION
When a failure occurs during automatic
testing, the unit will suspend operation
awaiting operator intervention.
When an automatic test fails, it will be repeated once. A
repeated test failure will cause “FAIL” to be shown on
the right display, with the corresponding test number to
the left.
The user may then press the DOWN ARROW to repeat
the test, the UP ARROW to skip to the next test, or the
PRE−TRIP key to terminate testing. The unit will wait in-
definitely or until the user manually enters a command.
CAUTION
When Pre−trip test Auto2 runs to comple-
tion without being interrupted, the unit will
terminate Pre−trip and display “Auto 2”
“end.” The unit will suspend operation until
the user depresses the ENTER key!
When an Auto 1 Pre−trip test runs to completion without
a failure, the unit will exit Pre−trip mode and return to
normal control operation. However, dehumidification
and bulb mode must be reactivated manually if required.
c. 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.
1. Individually selected tests, other than the
LED/Display test, will perform the operations
necessary to verify 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.
2. 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.
3. During Pre−trip testing, current limiting and pres-
sure limiting are both active, except during P−7
(High Pressure Switch Testing) when pressure lim-
iting is turned off.
d. Pre−Trip Test Results
At the end of the pre−trip test selection menu, the mes-
sage “P,” “rSLts” (Pre−trip results) will be displayed.
Pressing the ENTER key will allow the user to see the
results for all subtests (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 dis-
played.
Once all Pre-test activity is completed, dehumidification
and bulb mode must be reactivated manually if required.
4.8 PROBE DIAGNOSTICS
A complete temperature probe check is performed dur-
ing 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 nor-
mal operation. During normal operation, the controller
continuously monitors and compares adjacent temper-
ature probe readings.
The probe check procedure consists of running the
evaporator fans for up to eight minutes in order to com-
pare the readings from the adjacent temperature
probes. If a significant difference in temperature read-
ings is detected between probes, a defrost cycle, fol-
lowed 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 con-
trol.
In Perishable Mode, both pairs of supply and return
probes are monitored for probe disagreement. Probe
disagreement is considered a difference of 0.5C
(0.9F) or greater between the supply air sensors and/
or a difference of 2.0C (3.6F) 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 2.0C
(3.6F). 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 con-
trol.
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 1.2C (2.2F) dif-
ference 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 dis-
agree, 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 1.2C (2.2F) 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.
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