Carrier 69NT40-541-505 Operation And Service Manual page 75

Perishable Mode Pull
Down Test /
P8-1
eAutofresh CO
Sensor Calibration
Perishable Mode
P8-2 Maintain
Temperature 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
DTT Closed and
P9-0
Open Test
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Table 4–7 Controller Pre-Trip Test Codes
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. The left
display will read P81, the right display will show the supply air temperature. The
unit will then start to pull down the temperature to the 0C set point.
The test passes if the container temperature reaches set point before the 180-min-
ute timer expires.
On units where the CO
2
bration of the CO
tion will be attempted when the supply temperature goes below 5C. If the CO
sensor voltage reads within the 0.95 <>1.15Vdc range before the end of P8-1, the
sensor will be calibrated by holding the CO
bration 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
Test P81 must pass for P82 to execute.
A fifteen minute timer is started, and the system will attempt to minimize control
temperature error (supply temperature minus setpoint) until the timer expires. The
control temperature will be sampled each minute starting at the beginning of P82.
During P82, the left display will read P82, and the right display will show the supply
air temperature.
When the test is completed, the average control temperature error will be com-
pared 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 Data-
Corder supply temperature probe is invalid. If the test fails, the control probe tem-
perature will be recorded as -50.0C.
During P90 the defrost temperature sensor (DTS) reading will be displayed on the
left display. The right display will show the supply air temperature.
The unit will run FULL COOL for 30 minutes maximum until the DTT is considered
closed. Once the DTT is considered closed, the unit simulates defrost by running
the heaters for up to two hours, or until the DTT is considered open.
Test fails if:
The DTT is not considered closed after the 30 minutes of full cooling
HTT opens when DTT is considered closed or if return air temperature
rises above 248C (120F).
Test passes if the DTT is considered open within the 2 hour heat cycle time limit.
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Sensor Status indicates that a CO
2
sensor will be attempted during P8-1. Once P8-1 begins, calibra-
2
2
4–45
sensor is present, cali-
2
zero line low for 4 seconds. Once cali-
sensor calibration fails.
2
2
T-368