Fraunhofer ISE announced solution concepts for replacing gas and oil heating systems in multi-family houses with propane heat pumps. Developed with 20 heating industry and housing companies under the LC R290 project, the concepts include a central outdoor unit with 20% less R290 charge and 15% higher efficiency than comparable heat pumps.
The researchers evaluated buildings with heating loads ranging from 23 to 93 kW. The properties included both central heating systems and individual gas apartment heating, while available heat sources varied according to building layout, space constraints, hot water requirements, sound limits and safety requirements. The resulting concepts cover apartment-level and central heat pumps for indoor and outdoor installation, with an emphasis on compact systems requiring limited structural modification.
For centrally heated buildings, the project produced the reduced-charge outdoor demonstrator and a compact indoor brine-to-water heat pump using R290. The indoor model provides 28 kW of heating capacity at B0/W55. Its refrigerant charge was minimized to reduce the requirements placed on the installation safety concept.
A decentralized demonstrator was also developed for apartments connected to a shared hydraulic heat source such as geothermal energy, groundwater or low-temperature district heating. The unit has a heating capacity of 4.9 kW at B0/W55 and uses 150 g of R290, supporting installation in typical indoor locations such as kitchens and utility rooms. Apartment-level systems may be suitable where homes currently using individual gas heating are modernized separately.
Safety testing covered potential R290 leakage from indoor heat pumps. More than 100 discharge tests assessed five safety concepts and confirmed the ventilated enclosure approach described in EN 378 and IEC 60335-2-40. The project also examined chimney and drainage concepts for further development. Fraunhofer ISE will transfer the findings into the MAMMUT project, which is intended to create a software tool for selecting and designing heat pump systems for multi-family houses, including directly linked quotation generation for HVAC installers.
