Lithuanian OEM Refra has found that a new magnetic expansion valve, manufactured by Siemens, increases the winter time operation efficiency of 30kW (8.5TR) propane (R290) heat pumps by 16% compared to an electronic expansion valve.

According to Aleksej Pavšukov, Refra’s CEO, the new Siemens MVL702 valve allows the superheat control to be within 0.1‒0.2K (0.1°C/0.18°F‒0.2°C/0.36°F). Electronic valves control superheat to within 2‒3K (2°C/3.6°F‒3°C/5.4°F), making 7K (7°C/12.6°F) the normal temperature difference for heat pumps. The testing was performed under real weather conditions during winter in Lithuania, according to Refra.

“With the higher level of control, we can set the superheat values lower and get as close as possible to 5K (5°C/9°F) to obtain only the useful superheat,” Pavšukov said in an exclusive video interview with Marc Chasserot, Co-Founder and Owner of ATMOsphere, publisher of Hydrocarbons21.com, at the Mostra Convegno Expocomfort. The event was held March 12‒15 in Milan.

Pavšukov indicated that Siemens plans to officially release the magnetic valve by the end of April or the start of May. “Once Siemens announces the release, it will become standard in our heat pumps,” he said.

According to the product webpage, the MVL702 valve ‒ with applications for refrigeration cycles in chillers and heat pumps ‒ carries A3 certification for R290.

Efficiency and reliability

Europe’s adoption of F-gas regulations has led manufacturers to produce R290-based cooling and heating units. “Now everyone offers propane chillers and heat pumps, even those who did not have them a couple of years ago,” Chasserot said.

Pavšukov agreed with that assessment, adding that “the next step is to save electricity” by improving performance.

“The MVL702 magnetic expansion valve is fast, precise and robust, enabling up to 21% more heating capacity,” Siemens says in a video on the product webpage.

The valve features “minimal moving parts,” with the “normally closed function adding an extra layer of safety” to support using renewable energy sources, Siemens said in a press release

Unlike electronic valves, magnetic valves do not require supercaps to close, Pavšukov explained. “If the electricity turns off, the magnetic valve tightly closes; it will save the compressor in emergency operations.”

Refra ATMO approved

Refra recently became ATMO-approved, receiving the 2024 ATMO Approved Natural Refrigerants Label that marks the company as a best-in-class manufacturer of natural refrigerant systems and components, including those using propane, CO2 (R744) and ammonia (R717).

As a global market accelerator of clean cooling and heating solutions, ATMOsphere launched the label in June 2022, with requirements for annual reapproval.

“Refra plays an active role in partnering with different suppliers to test new innovative solutions to improve the efficiency of their systems,” Chasserot said. “We are really happy to have them join the family of best-in-class manufacturers working with natural refrigerants.” 

“[We] pride ourselves on being at the forefront of innovation, and our alignment with the ATMO Approved Label signifies our dedication to promote natural refrigerants,” Pavšukov said.

Established in 1994, Refra provides refrigeration and air-conditioning solutions for the European market, with 80% of its cooling production using the natural refrigerants ammonia, CO2 and propane.

“With the higher level of control, we can set the superheat values lower and get as close as possible to 5K to obtain only the useful superheat.”

Aleksej Pavšukov, Refra CEO