02 March 2026
|
Luke Begley, Installation Manager at IMS Heat Pumps, shares with us a project which used an unconventional mine-water heat source to achieve real-world performance that significantly exceeds typical Ground Source Heat Pumps (GSHP) expectations.
GSHPs have long been recognised as one of the most efficient and reliable low-carbon heating technologies available. When correctly designed and installed, they offer consistent performance, low running costs and long service life. Yet despite these advantages, GSHPs are still sometimes perceived as complex or niche compared with air-source alternatives.
In my experience, that perception often comes down to unfamiliarity rather than limitation. Some of the most impressive results I’ve seen from heat pump systems have come from ground source installations where the site conditions, system design and commissioning have been treated as a single engineering challenge rather than a set of standard components.
One such project is Stillwaters, a newbuild home in North Yorkshire that recently won Heat Pump Project of the Year at the H&V News Awards. Delivered by myself and a skilled team of IMS Heat Pumps engineers, the project uses an unconventional minewater heat source to achieve real-world performance that significantly exceeds typical GSHP expectations.
Understanding the site
The Stillwaters property is located within a Victorian woodland estate In North Yorkshire, set in an Area of Outstanding Natural Beauty. From the outset, it was clear that this would not be a standard domestic installation. The client was committed to a low-carbon heating solution that would sit discreetly within the landscape and avoid the visual and environmental compromises associated with oil or LPG.
With no access to mains gas, a heat pump system was the obvious route. However, traditional GSHP approaches such as boreholes or extensive horizontal ground loops presented challenges due to the sensitivity of the site and the desire to minimise disturbance.
What made this project unusual, and ultimately highly successful, was the presence of a disused lead mine on the land. The mine produces a continuous f low of underground water, and early investigations suggested that this water maintained a stable temperature throughout the year. Rather than seeing this as an obstacle, we recognised it as a genuine opportunity.
Why mine water makes sense
From a heat pump perspective, source temperature stability is everything. The more stable and favourable the source temperature, the lower the temperature lift required by the compressor, and the higher the system efficiency.
Underground mine water offers exactly that. Unlike rivers or surface ponds, which closely follow seasonal air temperature changes, mine water is insulated by the surrounding geology. This makes it particularly well suited to heat pump applications, provided it is handled carefully.
Our approach was to design a bespoke system that could extract energy from the mine water without disrupting its natural f low or the surrounding environment. A custom reservoir was constructed to house a Nuenta Energy Blade collector, allowing heat to be transferred efficiently while maintaining separation between the mine water and the closed heat pump circuit.
Getting this element right was critical. Flow rates, reservoir volume, freeze protection and long-term resilience all had to be carefully considered. The performance gains only materialise if the source behaves predictably over time, so we invested heavily in the upfront engineering.
Designing for low temperatures
At the heart of the installation is a NIBE S1155-16 kW three-phase GSHP. The property has a peak heat demand of 11.18 kW at a design outdoor temperature of –4.7 °C, and from the outset the goal was to keep flow temperatures as low as possible.
We designed the system around a 36 °C design flow temperature, which immediately places greater emphasis on the emitter side of the system. To achieve this, underfloor heating was installed throughout the property’s 307 m² floor area. Every room was calculated individually, with pipe spacing adjusted between 100 mm and 200 mm depending on heat loss, floor construction and finish.
This level of detail is essential. Low flow temperatures are not something you simply “set” on a heat pump, they are enabled by correct emitter sizing and distribution design. If that work isn’t done properly, system efficiency inevitably suffers.
Domestic hot water is provided via a 300-litre high-gain unvented cylinder. The cylinder selection and control strategy were chosen to balance efficiency with real-world usability, ensuring reliable hot water delivery without excessive reliance on immersion heating.
Controls and commissioning
Modern GSHPs are extremely capable, but they still rely on good commissioning to deliver their full potential. At Stillwaters, the control strategy includes internal room sensing, an external temperature sensor and weather compensation, allowing the heat pump to modulate smoothly rather than operating in a simple on-off fashion.
Remote connectivity also plays an important role. It allows us to monitor performance, check operating conditions and fine-tune settings after handover. For complex systems like this, commissioning doesn’t end when the system is switched on - it’s an ongoing process of optimisation.
As installers, this is where we add real value. A well-commissioned system not only performs better on day one, but it also continues to perform better over its lifetime.
Delivering the installation
The project took around ten months from initial survey to final commissioning and handover. Alongside the heating installation, the build required close coordination with civil works, plantroom layout planning, and careful routing of pipework to protect the surrounding environment.
Leading the installation alongside our team of heating engineers, my role was to ensure that the design intent was delivered accurately on site. On projects like this, clear communication and planning are just as important as technical knowledge.
You don’t get many second chances when you’re integrating a bespoke heat source into a protected setting, so attention to detail is key.
Performance in practice
Since commissioning, the system has exceeded expectations. The installation is currently achieving a Seasonal Coefficient of Performance (SCOP) of 6.2, comfortably outperforming the original design estimate. This level of efficiency is the result of several factors working together: a stable mine-water source, low-temperature underfloor heating, inverter-driven modulation, and careful commissioning. None of these elements on their own would deliver the same outcome, it’s the combination that matters. From the homeowner’s perspective, the benefits are simple and tangible: stable indoor temperatures, reliable hot water and significantly reduced running costs compared with fossil-fuel alternatives.
From an installer’s perspective, it’s a strong example of what GSHPs can achieve when they are treated as engineered systems rather than off-the-shelf products.
Key lessons for GSHP installers
Looking back on the project, a few lessons stand out:
- Don’t overlook unconventional sources: Stable water sources such as mine water can deliver exceptional results when properly engineered.
- Emitter design is critical: Low flow temperatures don’t happen by accident; they are designed into the system.
- Commissioning matters: Real-world performance is won or lost during commissioning and early operation.
- Collaboration pays off: Complex GSHP projects benefit hugely from close coordination between designers, installers, and other trades.
Looking forward
As the heating industry moves towards net zero, GSHPs will play an increasingly important role, particularly in projects where long-term efficiency, reliability and low carbon impact are priorities. Installations like Stillwaters demonstrate that ground source systems still have enormous untapped potential, especially when installers are prepared to engage with site-specific challenges and think creatively about heat sources.
For me, this project reinforces why GSHPs remain such a compelling technology. When they’re done properly, they don’t just meet expectations, they exceed them.
