www. refrigerationandaircon. co. za RACA Journal I November 2025 31
Project control logic have further cemented the role of rooftop units( RTU) by providing robust and smart digital control platforms to dynamically manage capacity and improve part load performance via staged and precise refrigerant electronic expansion valve( EEV) metering. This ensures accurate superheat control under variable ambient or return air conditions.
SINCLAIR AND SRF RTU RANGE OVERVIEW Sinclair is a European brand distributed by Beijer Ref AB in various countries across the globe, offering a key high-quality product for more than 20 years. Metraclark a division of Beijer Ref Africa( the largest air-conditioning and refrigeration wholesaler in southern Africa), gained exclusive distribution rights to Sinclair’ s collective portfolio since 2021.
Sinclair offers the SRI inverter range with a maximum cooling capacity on offer of 105kW. The Sinclair SRF range beyond 105kW is, however, only offered in a fixed-speed configuration, ideally offering cooling for large format commercial applications in the capacity range from 140kW – 370kW. The design offers both an integral and split configuration, with the latter offering flexibility for constrained rooftop spaces, supporting a piping distance of up to 40m between evaporator and condenser – should plantroom space serve as a key installation limitation.
Key features include a V-shaped condenser coil utilising internally threaded copper tubing with slotted fins, which enhances heat exchange efficiency while reducing the system’ s operational footprint. The coil is further treated with Golden Fin anti-corrosion treatment, tested to withstand up to 1 500 hours of salt spray exposure. Additionally, the unit ' s sandwich-structured paneling with PUR core insulation achieves a thermal conductivity of 0.024 W / m ° C and airtightness rated at EN 1886 Class TB1, delivering excellent thermal insulation and acoustic dampening.
Complimenting the core unit operations is the precise and rapid load matching response to changing load conditions is achieved via multi-stage compressor control regulations, via adjustments of EEV operations within 500 precision control step bandwidths.
SAFETY, CONTROL AND COMFORT FEATURES A major highlight of the Sinclair SRF280 is its robust safety and control system. Multiple layers of protection include high- and low-pressure switches, overcurrent and overload safeguards, phase failure detection, and dry contacts for fire system integration. Efficient comfort is enhanced using large diameter axial and centrifugal fans, which contribute to lower noise levels while maintaining high airflow efficiency. The embedded electronic expansion valve features 500-step control accuracy modulation, ensuring precise refrigerant regulation. Furthermore, the RTU supports Building Management Services( BMS) integration via BACNET protocol and features touchscreen interface for local operation, including real-time performance monitoring, fault alerts, and maintenance reminders.
Figure 2: Shoprite plantroom final installation( air-view).
SINCLAIR MODEL SRF TECHNOLOGICAL ADVANCES To further highlight engineering insights behind large-scale rooftop units such as the Sinclair Model SRF range, the following technologies reflect innovations designed towards enhancing thermal performance, energy efficiency, and indoor climate control:
• Uniform cross-flow and two-stage evaporation technology: At full load conditions, superior heat exchange performance is achieved and maintained by incorporating large-finned evaporators in a staggered, yet symmetrical alternating structure towards ensuring uniform performance. At part load conditions, the flow path is altered between evaporator supply paths as part of a rotation cycle. This temperature-based rotation of heat exchange enhances overall system heat transfer and enhances part load efficiencies. Sinclair Model SRF evaporators are engineered to maintain a face velocity between 2.5 – 3m / s, serving as a fundamental design criterion to be maintained in the application of latter two-stage evaporator coil technology, supporting lowtemperature air supply demands while enabling staged dehumidification performance.
• Three-variable co-ordination and precision control technology: Although fixed-speed in operation, the Sinclair Model SRF rooftop unit is engineered for responsive thermal regulation through co-ordinated control of airflow, refrigerant expansion and heat exchange. This three-variable interaction enhances cooling precision and
Figure 3: 1 / 4 Danfoss CH290A4BSA scroll compressors.
www. refrigerationandaircon. co. za RACA Journal I November 2025 31