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Support
EVACUATION We use the deep evacuation method to evacuate the system. The vacuum required is less than 500 micron using the same evacuation methodology as typical refrigeration systems( HCFCs, HFCs, HCs, etc).
CHARGING Charging refrigeration systems utilising R744 is similar to conventional systems, but there are additional insights needed, and some special tools for CO2( R744) are needed due to the high pressures involved.
Caution: as the pressure of the vacuum is below the triple point, dry ice formation is possible. It is therefore important to fill R744 into a system as a vapour to up to a minimum of 6 bars( 600kPa). Note: Some equipment manufacturers recommend 10 bar. Only then is it possible to fill liquid. Typically, a charging scale is used to add refrigerant in accordance with manufacturers’ specifications. Conduct a leak test using a suitable electronic leak detector.
COMMISSIONING The machine and the function of all safety elements and all electrical equipment has to be tested before operation. The testing process begins with a comparison of the unit specifications and the actual system. Assure whether the documentation is complete: operation manual, maintenance manual, diagrams and electrical drawings.
The next step is inspection of the system:
• The function of the safety relief valves should be tested with dry nitrogen before they are installed. The response value is the maximum allowed pressure PS of the section, for example, suction of intermediate pressure stage is 45 bar( 4 500kPa) or for the gas cooler 110 bar( 11 000kPa).
• The safety pressure switches are tested through a highpressure fault. The response value is equal to or less than 0.9 × PS.
The results must be documented in test reports. The following points are a checklist for testing a refrigeration system:
• Inspect all components for any damage
• Check the accordance with the specifications
• Inspect the safety equipment
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RACA Journal I November 2025 www. refrigerationandaircon. co. za