Germany’s Ait-group has unveiled two residential propane (R290) heat pumps with a refrigerant charge of just 150g, allowing for safe operation in indoor residential applications without the need for a separate ventilation system.
This approach results in a more space-efficient and cost-effective solution for domestic heating, according to the manufacturer.
The new models – the WZSV 63 from ait’s premium Alpha innotec brand and the WSV 6.3 from its economical NOVELAN line – are the first market-ready products to be developed under the LC150 research project, a collaborative effort led by the Fraunhofer Institute for Solar Energy Systems (ISE). Launched in 2020, the project focused on designing R290-based heat pumps with significantly reduced refrigerant charges.
In 2022, the LC150 project team announced it had developed a prototype that achieved 12.8kW (3.6TR) of heating capacity with only 124g of propane. Ait-group is the first industry partner to successfully develop a market-ready product based on the project’s foundational research. Building on that work, Ait-group translated the research into reality.
“Our goal was to apply the project’s findings directly to the development of the next generation of high-efficiency, environmentally friendly heat pumps,” explained Edgar Timm, Director of R&D at Ait-group. “We are very proud that our development team has achieved a technological breakthrough in this important field in such a short time.”
The two heat pump models have been available through authorized distributors since June.
“We are delighted that the new products from Ait-group are expanding the range of applications for propane heat pumps and making it easier to use natural refrigerants indoors,” added Clemens Dankwerth, Product Manager for Building Heat Pumps at Fraunhofer ISE.
“We are delighted that the new products from Ait-group are expanding the range of applications for propane heat pumps and making it easier to use natural refrigerants indoors.”
Clemens Dankwerth, Product Manager for Building Heat Pumps at Fraunhofer ISE
Indoor operation
To comply with safety regulations for indoor use, no more than 150g of propane refrigerant can be released in the event of a leak, an Ait-group representative told NaturalRefrigerants.com. To meet this requirement, R290-based heat pump systems typically require either active ventilation or a reduced refrigerant charge.
Ait-group’s new heat pumps address this challenge by adhering to the 150g–charge limit, enabling safe indoor installation without additional ventilation and significantly reducing installation complexity, cost and space requirements.
“Our new product line addresses specific practical requirements, providing planners, installers and consumers with a comprehensive and effective solution for challenging applications,” said Sjacco van de Sande, Ait-group’s Managing Director. “With this, we aim to actively contribute to the pragmatic and accelerated decarbonization of the building sector.”
Efficient performance
Despite their compact design, both models deliver heating capacities of 6kW (1.7TR) and flow temperatures of up to 75°C (167°F). Under average conditions, they achieve seasonal COPs of 5.14 at 35°C (95°F) and 3.96 at 55°C (131°F), according to Ait-group.
Both systems also offer optional cooling with capacities up to 7.5kW (2.1TR) and operate across a wide source temperature range of –13 to 30°C (8.6 to 86°F). Compatible heat sources include groundwater, ground loops, wastewater and photovoltaic (PV) thermal collectors.
The units also feature electric anodes for low maintenance and a modular design with a detachable refrigerant circuit, simplifying transport and installation in tight spaces.
Both models are home energy management systems (HEMS)-compatible and designed for seamless integration with solar PV and battery systems, supporting dynamic electricity tariffs and energy optimization.
Expanding R290 portfolio
In addition to its indoor line, Ait-group has launched two new monobloc air-source R290 heat pumps – Hybrox 21 and Helox 21 – for residential and light-commercial applications.
These systems are designed for retrofits and are capable of delivering water temperatures up to 78°C (172.4°F), which makes them suitable for older buildings with existing radiators. They are also suitable for multi-family buildings and larger hybrid heating systems, according to the manufacturer.
Each model offers up to 18kW (5.1TR) of heating capacity and can be installed in cascade configurations to meet demands up to 72kW (20.5TR). The refrigerant charge for the new Hybrox and Helox units has not been disclosed by the company.
The Hybrox 21 expands Alpha innotec’s Hybrox series, which previously covered 5–16kW (1.4–4.5TR) capacities.
