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9.5
Pressure testing
•
It is recommended to use inert gas such as nitrogen for pressure testing.
•
The pressure differential between the high and low side of the compressor should not exceed 30 bar (435
psig).
•
Test pressures are : 19 bar (275 psig) on the Low Side
28 bar (405 psig) on the High Side
9.6
Leak detection
•
Make sure that all isolation valves throughout the system are fully open.
•
Perform a leak detection using compatible refrigerant and pressurize nitrogen, detected by leak detector for
the applied refrigerant.
•
Never use CFC or HCFC refrigerants for leak detection of HFC systems.
•
Leak detecting additives shall not be used as they may affect the lubricant properties.
9.7
Evacuation & Charging
Once pressure testing has been completed, the system can now be evacuated to remove air and any
moisture from the piping. This can be done as follows:
•
Ensure any nitrogen charge is safely released from the system.
•
Connect a gauge manifold to the connections on the service valves on the condensing unit.
•
Connect a vacuum pump and vacuum gauge to the system.
•
Ensure all gauge manifold and service valves are open as required.
•
Evacuate the system until vacuum is below 250 microns (0.33 mbar).
Note: A triple evacuation procedure is recommended for all new systems or where moisture is
suspected
Once the system is isolated and the vacuum pump is switched off, any rise in pressure indicates that
either there may be a leak in the system or moisture is still present. In this case, recheck the system for
leaks, repair as necessary, and then restart the evacuation procedure. Once completed satisfactorily, the
vacuum pump and vacuum gauge can be removed.
At this point, the refrigerant charge can be added to the system as required. Refrigerants must be
charged in the liquid phase.
Charging of liquid into the suction side of the system should ONLY be
done with a metering device.
Use calibrated weighing scales to record the amount of refrigerant added
to the system.
Important Note:
Moisture prevents proper functioning of the compressor and the refrigeration system. Ensure
that a good quality vacuum pump is used to pull a minimum vacuum of 250 microns (0.33
mbar).
