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Project
Refrigeration plant room with adiabatic gas cooler on platform above.
A critical element was establishing seamless communication and control between the central refrigeration plant and the distributed AHUs. This was achieved through a collaborative partnership with CAREL, the control system provider. " Working closely with their team, we developed the specific programming and control logic, resulting in a bespoke system tailored to the facility ' s unique requirements." Throughout the design and implementation phases, the primary emphasis was placed on ensuring the safety and reliable operation of the integrated plant.
SYSTEM ARCHITECTURE Arnold detailed the integrated system ' s architecture: " The refrigeration system comprises two racks, with heat rejection to atmosphere managed by two adiabatic gas coolers. Stainless steel piping distributes CO₂ refrigerant to the blower coils and thereafter throughout the building to the refrigeration loads – including walk-in cold rooms, freezer rooms, perishable receiving and display cabinets on the sales floor – and also to the AHU. Conditioned air is then distributed via galvanised ducting and diffusers from these AHUs." A common liquid line network serves both refrigeration and air-conditioning components, and then a suction line to bring it back.
Sensors are positioned throughout the facility to monitor CO2 levels in the building and to detect leaks. A key energy efficiency measure is the utilisation of hot gas for heating. " Instead of directly rejecting heat to the atmosphere, it is first routed to the AHUs to provide heating for the store. Any residual heat not utilised by the AHUs is then rejected via the gas coolers on top of the plant. While hot gas defrost is a common refrigeration practice replacing electric heating, extending this principle to provide heating for the AHUs and the retail space, rather than direct atmospheric discharge, represents a significant energy recovery strategy."
A notable challenge during the project ' s initial phase was the absence of permanent power on-site. " This necessitated a phased commissioning approach, operating only a limited number of units at a time to ensure plant functionality." This constraint was
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RACA Journal I October 2025 www. refrigerationandaircon. co. za