Danfoss has tested the Sinop Triple Aqua CO2 heating and cooling system at its Application Development Center in Nordborg, Denmark, under calibrated heat pump test conditions. The report states that the unit reached a seasonal coefficient of performance (SCOP) of 3.56 when operated with a 20K (36°F) water temperature difference and a variable water outlet temperature. That was 24% better than the standard test conditions with a 5K (9°F) water temperature difference.
The testing covered intermediate-temperature heating under EN 14825:2022, comparable conditions adjusted for a larger water temperature difference, hot water production at 65°C (149°F) and 75°C (167°F), and standardized cooling conditions. Danfoss also reported a SEER of 2.81 for cooling mode operation.
According to the report, the 3-pipe CO2 system was developed in cooperation between Triple Aqua and Sinop, with Danfoss supporting the project with components and testing. The tested unit used two Bock HGX24/90-4 S CO2 T compressors with frequency control from 30 Hz to 70 Hz and a control system based on the Danfoss Alsmart platform. The refrigerant charge was 43.2 kg of R744 (CO2) (about 95.2 lb).
In cooling mode, the report says domestic hot water production lowered gas cooler pressure and improved performance. At 35°C (95°F) air temperature and 7°C (about 45°F) water supply temperature, the results indicated better cooling mode performance when domestic hot water was produced at the same time.
The document says the psychrometric chamber testing followed earlier functional testing in real outdoor air conditions, which was not part of the report. The findings are detailed in a Danfoss test report created on November 5, 2025.
