High-Efficiency Air Source Heat Pump Installation in a Large Northern Lincolnshire Home

Helping YOU find good heating engineers. We share case studies from engineers in the Guild of Master Heat Engineers to help people find top installers, help gas and oil engineers increase their knowledge around heat pumps, and provide a solution for third-sector professionals to understand the industry better.

Overview

Converting large rural properties away from oil heating is often described as a simple technology swap. In reality, it is a complex engineering exercise that quickly exposes whether a system has been properly designed or merely assembled over time.

This Northern Lincolnshire project involved replacing an ageing oil-fired boiler serving a substantial detached home with a high-efficiency air source heat pump. Rather than simply removing the old boiler, the installation was approached holistically: the system was carefully designed to integrate with the property’s existing solar PV array and large battery storage, optimising both performance and running costs.

The original oil system exhibited many of the issues commonly seen in long-established installations. Over decades, additional pumps, controls, and hydraulic workarounds had been added to solve short-term problems. While these may have addressed immediate issues, they left the system inefficient, difficult to commission, and nearly impossible to evaluate or monitor meaningfully.

Before any new equipment was selected, the entire heating system was reviewed from first principles. The goal was to create a system that allowed the heat pump to operate efficiently, predictably, and transparently; not just to replace a boiler. The design focused on simplification, removing unnecessary hydraulic complexity, rationalising circulation, and ensuring stable flow conditions to maximise compressor run times and reduce parasitic electrical consumption.

Domestic hot water was treated as a critical component rather than a secondary consideration. The system needed to provide reliable hot water capacity at lower temperatures, avoid unnecessary reliance on immersion heaters, and maintain high efficiency even during peak demand.

Finally, the system was designed to actively benefit from the property’s renewable energy infrastructure. Space heating and hot water production can now be timed to align with periods of solar generation or low-cost electricity, while the battery storage offsets grid import during higher tariff periods. Combined with OpenEnergyMonitor integration for full transparency and real-time performance data, the homeowner has clear insight into energy use, efficiency, and comfort.

This project demonstrates that heat pumps in large rural homes are not always a simple appliance swap; they demand careful engineering, thoughtful integration, and an evidence-based approach to achieve predictable, efficient, and comfortable performance.

Master Heat Engineer

Key Specifications

• Heat source: Vaillant Arotherm Plus 12 kW air source heat pump

• Heat Loss: 12kW @ -3 °C external temperature

• Design flow temperature: 42 °C @ -3 °C external temperature

• Integration: Solar PV array and large battery storage

• Monitoring: OpenEnergyMonitor for real-time and long-term data analysis

• Circulation: Rationalised to reduce parasitic electrical consumption.

System Design

Following a full heat loss assessment, the oil boiler was removed and replaced with a Vaillant Arotherm Plus 12 kW heat pump configured as the sole heat source. The system layout was simplified:

• Unnecessary hydraulic complexity removed

• Circulation rationalised

• Flow conditions stabilised to allow long compressor run times

• Design flow temperature: 42 °C @ -3 °C, ΔT flow/return of 5 °C

Domestic hot water was treated as a critical design component. A Cylinder was installed, capable of efficient heat transfer at lower flow temperatures, reducing compressor lift and eliminating the need for immersion heaters.

The heat pump system was integrated with the property’s solar PV and battery storage. Heating and hot water production can be timed to align with periods of solar generation or lower-cost electricity, offsetting grid import during peak tariff periods.

OpenEnergyMonitor provides transparent performance data for electrical input and thermal output, allowing ongoing optimisation and building confidence that the system is performing as intended.Performance and Results

PERFORMANCE & RESULTS

Heat Pump Operation

The Vaillant Arotherm Plus 12 kW maintains stable flow temperatures of 42 °C at -3 °C, with a ΔT of 5 °C, allowing long compressor run times and minimising short cycling. The system achieves strong efficiency figures relative to the size of the property and the low-temperature design requirements, demonstrating that heat pumps can perform effectively in large rural homes when properly engineered. Auxiliary electrical consumption is minimal due to hydraulic simplification and careful circulation design.

Domestic Hot Water Performance

The Cylinder provides reliable hot water capacity even during peak demand periods. Hot water production occurs without reliance on immersion heaters, reducing unnecessary electrical load and improving overall system efficiency. Flow temperatures remain stable during hot water draw-offs, avoiding the performance dips that are common in poorly designed large home heat pump systems.

Renewable Energy Integration

Space heating and domestic hot water production are timed to align with periods of solar PV generation, maximising on-site renewable energy use. Battery storage offsets grid import during peak electricity tariff periods, reducing running costs and improving energy resilience. Integration with the homeowner’s energy system allows dynamic optimisation based on available solar generation and battery charge status, rather than operating as a static electrical load.

Monitoring and Transparency

Real-time and long-term monitoring via OpenEnergyMonitor provides accurate measurement of both electrical input and thermal output. Data confirms that the heat pump operates predictably, efficiently, and in harmony with the building’s energy profile. The transparency of the monitoring allows ongoing fine-tuning of the system and builds confidence for both the homeowner and the installer.

Comfort and Practical Benefits

Internal temperatures remain consistent across all rooms and zones, even during prolonged periods of cold weather. Homeowner reports indicate improved comfort and reduced energy costs, reflecting the real-world benefits of careful engineering rather than theoretical efficiency figures. The system demonstrates that large rural homes can be served effectively by a single heat pump when the surrounding system, including piping, cylinder, controls, and energy integration, is properly designed.

The project shows that performance is determined not just by the heat pump itself, but by the quality of the system design, simplification of hydraulics, careful commissioning, and integration with renewable energy sources. The system operates efficiently, provides reliable domestic hot water, leverages on-site solar and battery storage, and delivers a comfortable indoor environment, all with measurable, transparent performance data.

Estimated Heat Loss (kW) at Various Outside Temperatures

Thanks to the Patrons

The Guild of Master Heat Engineers is supported by our Patrons.

Learn more about our Patrons here.

Podcast

Listen to James in an episode I did with him back in 2022. Here we both talk with Daniel Newport.

Daniel previously held a senior position at BEIS and was part of the team that introduced the target of 600,000 heat pumps by 2028. It is very interesting how that number was reached.

Closing Thoughts

It’s coming up to Christmas. Hope your heating system does not break down. Unfortunately, there will be people this happens too. And lots of engineers will be out there fixing them. We often take our heating systems for granted until they break down; and we often take heating engineers for granted. James, represents the engineers out there who are willing to keep learning and pushing the boundaries. He’s a very nice chap and it is a pleasure to feature him. Good work James! You are in the Guild and will be getting your seal…

Have a great week everyone.

Nathan

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