Carrier EverFRESH Operation, Service And Parts Manual page 20

Code Component Tested
P20-4 CO2 and O2 Sensor Calibration
Test Sequence: "CAL" will be displayed on the left display and a 10-minute countdown timer is displayed on the
right display. The unit will run High Speed Evaporator Fans.
Note: Calibration only run when AutCA selected. Skipped if P20 selected.
Pass Criteria: The CO2 sensor and O2 sensor will perform an auto calibration provided the sensor signal is valid
and values are consistent with ambient air.
Error messages when calibration fails:
The CO2 sensor will be validated and then needs to read between 0.9 and 1.15 VDC to ensure fresh air is
present in the sensor prior to calibration. If the level is not reached, "NoCAL" will be displayed.
If CO2 or O2 calibration fails, "O2 Fail" or "CO2 Fail" will be displayed and the test will stop.
The O2 sensor will be validated to verify it is within a specific range suitable for calibration. If voltage is out-
side of this range, "O2 Fail" is displayed.
During calibration, the stability of the sensor will be monitored and must be within 20mV over one minute to
ensure the sensing chamber is properly flushed with fresh air. If it's not stable, "NoCAL" will be displayed.
In the event of a "NoCAL", it indicates that fresh air is not going through the sensors. Verify there is no
cargo in the contained space, the sensor filter is not clogged and sensor hoses are properly connected.
Then re-run the Pre-trip "AutCA" test under the PRE-TRIP key menu.
P20-5 EverFRESH Nitrogen Valve (EN) Solenoid Test
Test Sequence: Test will start with EAC off. Energize EN and wait 5 seconds. Energize EAC. Test will run up to
an additional 300 seconds or until N2 reaches acceptable limit. Then the EAC and EN will be de-energized.
Pass Criteria: EN current is between 100 and 200mA. N2 concentration is at minimum acceptable level.
PTI Run in Units Configured for Optional CO2 Injection Kit
P20-6 CO2 Injection Valve Solenoid (CSV)
Test Sequence: Open the CSV and wait 5 seconds. Record CSV current.
Pass Criteria: CSV current is between 100 and 200 mA.
P20-7 CO2 Injection Pressure Transducer (IPT)
Test Sequence: Shut off all machinery outputs. Validate the transducer is present. Validate the transducer at 0.0
PSIG.
Pass Criteria: Validate that the IPT reads between -5 and 5 PSIG.
T-374
Table 3–1 Pre-Trip Test Codes (Continued)
3–4