St. Olav Hospital in Trondheim, Norway, retrofitted the numerous cold rooms for its laboratory, on-site hotel and canteen with a CO2 (R744) installation, complete with advanced controls and variable frequency drives (VFDs) to optimize energy efficiency and enhance system accuracy.
Sinop, a refrigeration manufacturing company in Czechia, designed and implemented the system. The installation included three refrigeration packs that were installed in June: a 20kW (5.7TR) medium-temperature (MT) pack plus two linked booster packs of 10kW (2.8TR) medium temperature and 5kW (1.4TR) low temperature. The project also features 12 evaporators.
Sinop incorporated Reftronix CO2 controllers for the refrigeration packs and cold rooms and Invertek’s Optidrive Eco VFDs for the compressors. (Reftronix and Invertek have been working together for several years, formally announcing a partnership in 2018.)
The combination of controllers and VFDs ensures the precise control of the complete refrigeration process as well as remote access to live data, alarms and settings, according to a statement by Invertek.
“To go with Reftronix and Invertek Drives was really a very easy decision,” said Kjell Robert Overlev, the Founder of Sinop Technoblock, said. “Their solutions and full integration with the inverters set them miles ahead of the alternatives.”
The Optidrive VFDs accurately control the speed of the compressors, depending on the temperature required and other conditions, said Invertek. This data is picked up by the controller, which communicates with each of the drives. “Optimizing the speed of each of the compressor motors makes them more energy efficient than the conventional start/stop used in HFC refrigerant systems,” added Invertek.
Graphical overview
The Reftronix controller is capable of measuring temperatures and pressure, calculating optimal performance, adjusting the speed of the compressor through the Optidrive VF and adjusting the opening of electronic valves and the speed of the fan, said Reftronix.
“The controller user interface is a web page, which makes it easy to commission and provides a good graphical overview of the run-time conditions,” said Overlev. “All the controllers are on the same ethernet network.”
This means you can link the controller webpages, making it possible to look at a pack and with the press of a button you can view the cold room controller, he explained. As a result, there is no need for a system manager or front end, which saves a lot of upfront costs. Any alarm or trip warnings are also highlighted via the webpage.
Henrik Christensen, General Manager at Reftronix, said the combination of their controller and the VFD ensured the refrigeration system was as accurate and efficient as it possibly could be. “The new refrigeration systems at St. Olav Hospital are a great demonstration of how CO2 HVAC&R systems are not only helping reduce energy use and creating greater efficiencies but are supporting the work in reducing harmful emissions and climate change,” he said.
“CO2 HVAC&R systems are becoming more widespread in cooling and heating systems,” said Invertek. “This is due to the push globally to phase out synthetic HFC systems, which are some of the world’s worst polluters. Large-scale refrigeration users, such as retailers, are already converting to CO2 refrigerant systems to reduce energy consumption and meet tighter emission regulations.”
“The new refrigeration systems at St. Olav Hospital are a great demonstration of how CO2 HVAC&R systems are not only helping reduce energy use and creating greater efficiencies but are supporting the work in reducing harmful emissions and climate change.”
Henrik Christensen, Reftronix
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