PROJECT
INCORPORATING COLD CHAIN
Custom built walk around chiller.
" 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
This facility features a unified system where the chilled water AHUs have been replaced with direct expansion( DX) AHUs.
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 benefits in terms of both energy efficiency and environmental impact. CO2 refrigerant has a Global Warming Potential( GWP) of one. Furthermore, from an energy efficiency perspective, we anticipate potential savings in the range of 20 – 25 % on operational electrical consumption." The total cooling capacity of the integrated plant is approximately 1 600 kilowatts( split between air conditioning and refrigeration).
The AHUs and refrigeration racks were built and supplied by Heating Centre( HC Group), a key manufacturer possessing the capability to produce CO2-compatible coils engineered for high-pressure applications, specifically cooling coils rated at a 60 bar design pressure and heating coils rated at 130 bar. To accommodate the high pressures associated with CO2 refrigerant, stainless steel piping was utilised throughout the system, with K65 copper specified in instances where copper was deemed necessary. The blower coils within the cold and freezer rooms were also sourced from HC. The control system is managed by CAREL, and the compressors are Danfoss Bok semi-hermetic models.
The implementation of this innovative integrated system presented notable complexities. " The process was certainly not straightforward, requiring significant effort in integration, particularly as a first-of-itskind application requiring complex control logic. Close collaboration between the refrigeration and air conditioning contractors was essential," Arnold elaborated.
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.
Refrigeration rack A within plant room.
24 www. coldlinkafrica. co. za COLD LINK AFRICA • November / December 2025