Instead of using a fluid to transfer the heat through submerged, sealed pipes, an open loop system takes water from a borehole, lifting it to the surface, extracting heat energy and then returning the cooled water to a separate borehole.
However, as there is no anti-freeze, there is a potential risk that open loop system pipes could freeze as colder water leaves the heat pump. It’s therefore important that there is enough flow of water and correct sizing of the heat pump installation to ensure this does not happen.
Open loop systems move large volumes of water through the heat exchanger – higher than might be possible with a closed loop system. As a result, open loop WSHPs are often more efficient than equivalent ground or air source heat pumps. However, they also have higher operation and maintenance costs – so you need to factor this in when thinking about total running costs. Your installer should be able to offer you advice on working with either open or closed loop systems based on your specific site location.
In both systems, electricity is needed to power the compressor, but the amount of heat energy delivered to your home is more than the amount of electricity used by the system. This means that installing a heat pump could reduce your energy bills and carbon emissions.