Test Tightness (Pressure Test); Test For Noncondensables - Fieldpiece SMAN SM480V Operator's Manual

Test Tightness (Pressure Test)

After working on a refrigerant-side component
of an emptied system, it's a good idea to
pressurize the system with dry nitrogen and
check for pressure drops before evacuation
1. Pressurize the system with dry nitrogen. Pressure levels vary with
the equipment you're testing. Always check with the manufacturer.
2. Connect the low side (suction line) port to the system and wait for
the pressure to stabilize. You can connect the high side (liquid line)
as well to help monitor stability, but the pressure differential (P.diF)
calculation is only using the low side sensor.
3. Attach SLT clamp to the pipe you're going to pressurize.
This temperature is used to compensate for any temperature changes
between the start and end of the test.
To deactivate temperature compensation, unplug or unassign SLT
before starting the test; SLT will not be shown or used.
4. Press TEST TIGHTNESS to prepare test.
5. Press ENTER to start the test.
The stopwatch starts.
Real-time compensated pressure change is labeled P.diF.
Real-time temperature is labeled SLT.
Real-time temperature change is labeled ΔT.
6. Press ENTER to stop the test.
The stopwatch, P.diF, and ΔT freeze.
If P.diF is negative, there may be a leak in the system.
If P.diF is positive, SLT or nitrogen temperature may be unstable.
High and low side pressures and SLT continue to display, but they are
no longer being used.
7. Press ENTER to exit the test.
• To save battery life, the screen will turn off after 3 hours of testing,
but will continue to test. Press any button to turn the screen on.
20

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 efficiency, 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
1. Use ARROWS to select the system refrigerant.
2. Unpower the compressor, but allow the condenser fan to run.
3. Connect high side port to the system to view system pressure.
4. Clamp one thermocouple to the discharge line.
5. Clamp the other thermocouple to the liquid line.
6. Clip the ODDB thermocouple to measure the air entering the
condenser.
7. Monitor all three temperatures until they all stabilize and show the
same value.
8. 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.
21