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T-318
3
−
39
Table 3-7 Temperature Controller Pre-Trip Test Codes (Sheet 4 of 6)
P7 Tests - High Pressure Tests:
Unit is run at full capacity without condenser fan running to make sure that
the HPS opens and closes properly.
P7-0 High Pressure
Switch Closed
With the unit running, the condenser fan is de-energized, and a 15 minute timer
is started. The right display shows discharge pressure if the unit is equipped with
a discharge pressure transducer (DPT). If no DPT is installed, the condenser
pressure transducer (CPT) reading will be displayed.
T
est is skipped if:
Sensed ambient temperature is less than 7
°
C (45
°
F)
Return air temperature is less than -17.8
°
C (0
°
F)
The water pressure switch (WP) is open, indicating that the unit is operating
with a water-cooled condenser
Test is skipped if the unit does NOT have:
A compressor discharge sensor (CPDS)
A discharge pressure transducer (DPT)
A condenser pressure transducer (CPT)
Test passes if the HPS opens within 15 minutes.
Test immediately fails if the following inputs are sensed to be invalid:
Compressor discharge sensor (CPDS)
Discharge pressure transducer (DPT)
Condenser pressure transducer (CPT)
Return temperature sensor (RTS)
Ambient sensor (AMBS)
Test will also fail if:
HPS fails to open within 15 minutes
Discharge temperature exceeds 138
°
C (280
°
F)
Discharge temperature is less than or equal to ambient temperature plus
5
°
C (9
°
F)
CPT or DPT pressure exceeds 27.42kg/cm
2
(390psig)
P7-1
High Pressure
Switch Open
Test P7-0 must pass for P7-1 to execute.
The condenser fan is started and a 60 second timer is started.
Test passes if the high pressure switch (HPS) closes within the 60
−
second time
limit, otherwise, it fails.
P8 Tests - Perishable Mode Tests:
Pretrip tests P7-0 and P7-1 must have passed or have been skipped for
these tests to execute.
P8-0
Perishable Mode
Heat Test
If the container temperature is below 15.6
°
C (60
°
F), the set point is changed to
15.6
°
C, and a 60
−
minute timer is started. The left display will read “P8-0.” The
control will then heat the container until 15.6
°
C is reached.
If the container temperature is above 15.6
°
C at the start of the test, then the test
proceeds immediately to test P8-1 and the left display will change to “P8-1.”
The test fails if the 180
−
minute timer expires before the control temperature
reaches set point. The display will read “P8-0,” “FAIL.”