Carrier 69NT40-561-399 Operation And Service Manual page 93

P8 Tests - Perishable Mode Tests: Pretrip tests P7-0 and P7-1 must have passed or have been skipped for these
tests to execute.
CODE TITLE
P8-0 Perishable
Test
P8-1 Perishable
Pull Down Test /
eAutoFresh
Sensor Calibration
P8-2 Perishable
Maintain Tempera-
ture Test
P9 Test - DTT Close and Open Test: The DTT in this control is not a physical device, with actual metallic con-
tacts, it is a software function that acts similar to a thermostat. Using various temperature inputs, the DTT function
determines whether a thermostat mounted on the Evaporator Coil would have OPEN or CLOSED contacts. Pri-
marily, the DTT function operates based on the temperature reading from the Defrost Termination Sensor.
DESCRIPTION
Mode If the control temperature is below 15.6°C., the setpoint is changed to
15.6°C., and a 180 Minute timer is started. The control will then be placed in
the equivalent of normal heating. If the control temperature is above 15.6°C.
at the start of the test, then the test proceeds immediately to test 8-1. While
in test 8-0 the right display will show the value of the control temperature."
The test fails if the 18°0 Minute timer expires before the control temperature
reaches setpoint - 0.3°C. If the test fails, it will not auto-repeat. There is no
pass display for this test. Once the control temperature reaches setpoint, the
test proceeds to test 8-1.
Mode Control temperature must be at least 15.6°C (60°F).
The set point is changed to 0°C (32°F), and a 180-minute timer is started.
CO
The left display will read "P8-1," the right display will show the supply air tem-
2
perature. The unit will then start to pull down the temperature to the 0C set
point.
The test passes if the container temperature reaches set point before the
180-minute timer expires.
On units where the CO
ent, calibration of the CO
begins, calibration will be attempted when the supply temperature goes be-
low 5°C. If the CO
before the end of P8-1, the sensor will be calibrated by holding the CO
line low for 4 seconds. Once calibration is performed, the sensor voltage will
be verified to make sure it is in the 0.95 to 1.05 Vdc range. If the voltage is
not within this range, CO
Mode Test P8-1 must pass for P8-2 to execute.
A fifteen minute timer is started, and the system will attempt to minimize con-
trol temperature error (supply temperature minus setpoint) until the timer ex-
pires. The control temperature will be sampled each minute starting at the
beginning of P8-2.
During P8-2, the left display will read "P8-2," and the right display will show
the supply air temperature.
When the test is completed, the average control temperature error will be
compared to the pass/fail criteria.
Test passes if the average temperature error is within +/- 1.0°C.
Test fails if the average temperature error is greater than +/- 1.0°C, or if the
DataCORDER supply temperature probe is invalid. If the test fails, the control
probe temperature will be recorded as -50.0°C.
Sensor Status indicates that a CO
2
sensor will be attempted during P8-1. Once P8-1
2
sensor voltage reads within the 0.95 <>1.15Vdc range
2
sensor calibration fails.
2
4–59
sensor is pres-
2
zero
2
T-365