Project: Arisaig Ground Source Heat Pump

Technologies: Heat Pumps

Contact: Graham Moss


New build 4 bedroom house, approx 250 m2

Technology installed:

A NIBE 8 kW F1145 ground source heat pump with a 300 litre NIBE VPB 300 hot water cylinder. The hot water cylinder is also heated by NIBE SOLAR FP215 solar thermal collectors.

A 100ltr buffer cylinder

NIBE FLM Heat Recovery Unit

Installation Date:

March 2013

How it works:

A ground source heat pump works by pumping a mix of water and refrigerant, with a low boiling point, through looped underground pipes. The mix of water and refrigerant absorbs the heat from the ground (usually between a steady 8-12ºC). A heat exchanger then extracts the absorbed heat and transfers it to the heat pump to warm the water of the heating and/or domestic hot water.

The underground loop for this installation has been placed in a 180m borehole. Additionally the water/refrigerant mix passes through a heat recovery unit which extracts heat from the house ventilation system. The greater the difference in the starting temperature of the liquid to the final heating temperature means the harder the heat pump has to work, therefore this slight increase in temperature from the Heat Recovery unit improves the efficiency of the heat pump.

In this installment space heating is done via under floor heating. The chosen room temperature is selected via a digital display (on the heat pump or a remote control attached inside the house). The pump then takes into account the current outside and inside temperature to adjust the flow temperature to the under floor heating. The layout of the pipes under the floor determines individual room temperatures (for example a room that requires a cooler temperature would have less pies in the layout than one which wish to be more cosy).

Who installed it?

Lochaber Renewables

Installation cost:

£7,000 for bore hole, £13,000 for heat pump and associated parts, including installation.

Grant/finance received/will receive (FiTs/RHI etc):

Will be eligible for the domestic Renewable Heat Incentive payments from spring 2014, current expected tariff is 18.8p/kWh for GSHP. Approximate amount expected according to heating requirements on EPC. In this property, the expected RHI income will be £3,500pa for 7 years from the heat pump and approx £500pa from the Solar Thermal panels.

Any planning issues:


Noise/smell issues

When the pump was running the noise level was equivalent to that of a fridge.

Onward running costs/needs:

The heat pump requires electricity to circulate the water/refrigerant mix around the loop. This costs around 50p per hour regardless of what temperature you want your house heated to. The heat pump was installed in March this year. Running costs for the period April-September were £157 (averaging at £30). Graham predicts that the pump should use cost approx. £700 per year to operate

Owner’s comments/advice

Although ground source heat pumps are a bit more work to install, Graham says that they are more efficient and that once they are in, there a fewer issues with them.

Recommend the technology:


If you would like to speak with the owner about his project please email Graham Moss – [email protected]

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