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Ground Source Heat Pump Case Study


In the heart of the Kent Downs Area of Natural Beauty lies the rural village of Plaxtol and this quaint public house conversion. Built in the 1700s, this property is now home to Steve Light, providing a spacious four-bedroom home for his family to enjoy. The charming pub conversion is located near a spring which was historically used by the pub for brewing beer and cider. Steve’s home was originally heated by oil, but he recognised the need to switch to an alternative heating system that reduced both carbon and energy costs.

The Solution

This home was already kitted out with insulation, but the installation of a NIBE S1155 12kW ground source heat pump (GSHP) has massively boosted the sustainability of the property. The retrofit of this open loop GSHP installation uniquely diverts water from the spring, that previously provided water for beer and cider brewing, into a break tank. A submersible pump controlled by a dual float switch maintains the level of water in the tank. The water was monitored before the heat pump installation to ensure that the flow and temperature of the spring was constant and sufficient to support the GSHP. An abstraction license was granted by the Environment Agency that allows the water to be pumped out of the spring.

Invicta Clean Energy Ltd, a NIBE Pro Partner, fitted the NIBE heat pump which is connected on its brine side to the water from the break tank via a plate heat exchanger. Once water from the break tank has been circulated through the heat exchanger and between 5 and 8°C of heat has been extracted by the heat pump, it is discharged back to the source a little lower down to resume its flow downstream, albeit at a lower temperature – a sustainable, seamless system.

The break tank fed by the spring also supplies hot and cold water for domestic use thanks to a mains booster pump and a UV filter. The heat pump works alongside a NIBE VBP S300 hot water storage cylinder so the property is always warm and there is hot water on demand. This project only took 2 weeks to install, providing the family with a reliable, low carbon heating and hot water system.

The Results

The natural spring is able to provide the property with a steady brine temperature of ~10°C. This gives the heat pump a Seasonal Coefficient of Performance (SCOP) of 4.43, meaning it works well at both low and high temperatures. If there are any issues, the system is remotely monitored by NIBE’s MyUplink portal that can email alerts to the user in any emergency situations. This portal has an added bonus of being able to track and control the heating system.


“The best thing about this NIBE heat pump is its reliability and the technical support provided during and post installation. Steve’s new energy system not only allows his carbon footprint to be reduced, but it is helping him to save money on his energy bills, supported by funding from the domestic Renewable Heat Incentive.” Invicta Clean Energy Ltd (installer)

About the installer

Invicta Clean Energy Ltd specialise in the installation and design of multiple renewable energy technologies, including heat pumps, biomass systems, solar thermal and photovoltaics. Their expertise allows them to identify the most appropriate technologies that best match the energy requirements of buildings and the lifestyle of their clients. Invicta Clean Energy Ltd are a fully trained NIBE Pro Partner installer.

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