The Old Farmhouse

Ground Source Review The Old Farmhouse: Pond Mats

Ground Source Review: The Old Farmhouse.

The owners of the Old Farmhouse in Lancashire replaced their old, inefficient LPG boiler with a cascaded ground source heat pump system from Kensa to provide heating and hot water to three separate dwellings, thus benefiting from the Non Domestic Renewable Heat Incentive (RHI: this scheme has now closed – please visit this page to explore other funding).


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Ground Source Review: The Old Farmhouse

Harold Owen purchased the Old Farmhouse in Bickerstaff, Lancashire ten years ago. As well as establishing a successful farming business, he also completely renovated the c1900 farmhouse and converted the barn and stables into comfortable domestic dwellings. This included adding PVC double-glazing, plus wall, loft and floor insulation in line with current building regulations.

As part of this renovation, Harold was looking to replace his old, leaking LPG boiler which was proving inefficient and expensive to run. Having already had Solar PV installed to generate electricity and earn a payback via the Feed-in-Tariff, he was open to considering another renewable technology to provide heating and hot water to the three buildings.

He had an acquaintance who has a ground source heat pump installed, so had seen the system and heard about the benefits of the technology first-hand. Having made the decision to use ground source, Harold was on the look-out for a good team of installers. He partnered with renewable energy specialists and Kensa partner installer Atlantic Contracting Ltd.

As part of their consultation process, Atlantic Contracting advised Harold that ground source heat pumps work especially well with water sources where the heat transfer rate is higher than in the ground. This married up with plans Harold had for digging a large pond on land adjacent to the farmhouse that was of no use for crops. Initially he had wanted it as a water feature but when he also discovered he could use the pond as a heat source for the ground source heat pump, he was keen to go ahead.

To save money on the groundworks aspect of the installation, Harold had assistance from a friend with digging out the new pond which measures 30m x 20m and is around 8 foot deep. Together they dug out and clayed the pit to ensure it would hold water. The new pond has an adjacent river which provides a constant flow of water.

This was Atlantic Contracting’s first pond mat installation and was a great introduction to this type of heat collector. Initially the pond was pressure tested to ascertain whether there was a high enough flow rate to power the system. To avoid the pond mats becoming covered in silt which could obstruct the flow of water around the pipes, Atlantic Contracting suspended them a foot off the bottom of the pond on flat plastic trays and breeze blocks.

One of the more challenging aspects of the installation was that the main farmhouse had a driveway made up of old, uneven square cobbles that had been in place for hundreds of years and were set in tar. In order to dig the trenches required to run pipework from the plantroom to the heat pump, Atlantic Contracting dug up, and subsequently replaced, two metres of cobbles.

The farmhouse, barn and stables are all currently occupied and all three feature en-suite bathrooms with a demand for hot water. In order to meet the total 42kW heat load, Kensa specified a cascaded system featuring a 24kW Twin to provide space heating, in combination with a 21kW Hybrid, which in addition to providing heating, is specially designed to provide hot water to 65°C.

The heat pump units are housed in a plantroom in a barn where the LPG boiler was once connected. The new system incorporates the property’s existing wireless heating controls and has three zones so that the heating and hot water in each dwelling can be controlled separately. As the heat pumps are serving separate properties, the project is eligible for the Non Domestic Renewable Heat Incentive (RHI: this scheme has now closed – please visit this page to explore other funding) earning Harold quarterly payments from the Government over a 20 year period. Atlantic Contracting calculate that he will see a return on his investment within eight years.

Paul McCartney, Director of Atlantic Contracting Ltd, said: “It’s been brilliant working with Kensa. They give good customer service and any questions we had were answered straight away. The units are easy to install and we are keen to use them for more projects.”

Key Facts

  • Working agricultural farm and c1900 farmhouse;
  • Converted barn and stable buildings;
  • Cascaded ground source heat pump system;
  • 1x 24kW Kensa Twin Compact for heating;
  • 1x 21kW Kensa Hybrid for heating and hot water;
  • 12x pond mats submerged in pond.