21
Test for Noncondensables
If head pressure seems high even after cleaning
coils, optimizing airflow, and other routine
maintenance, you may have noncondensables
trapped in the system. Noncondensables can
reduce eciency, performance, and put extra
stress on system components. Noncondensables
can enter the system in many ways, and your initial
system service may be following years of poor
service that introduced the noncondensables.
20. Use ARROWS to select the system refrigerant.
21. Unpower the compressor, but allow the condenser fan to run.
22. Connect high side port to the system to view system pressure.
23. Clamp one thermocouple to the discharge line.
24. Clamp the other thermocouple to the liquid line.
25. Clip the ODDB thermocouple to measure the air entering the
condenser.
26. Monitor all three temperatures until they all stabilize and show the
same value.
27. View the subcooling (SC) calculation on the display.
The closer SC is to 0.0°, the fewer noncondensables are trapped.
Depending on the system, a negative SC may suggest a need to
recover, evacuate, and charge with virgin refrigerant.
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