Clifford Place ground source heat pump case study: slinky trench being dug

An installer’s indispensable list of GSHP essentials

With the Renewable Heat Incentive extended to 2021, the market opportunity for installers in this industry is strong.

Familiarisation with the strengths of each renewable heat technology ensures wider scope and profitability.

To help, Alison Harding and Darren Veal, Technical Support Engineers for Kensa Heat Pumps, have combined their years of ground source experience to offer an indispensable list of the essentials for any installer venturing into ground source heat pumps.

1. Energy Sources

One of the first and most important things to remember about ground source heat pumps (GSHP’s) is that your heat source options are not limited to just the ground. You can utilise water sources too, including lakes, rivers, ponds, streams, aquifers and even the sea. If the property that requires heating is next to any of the above water sources, then subject to volume and flow rate they could support very efficient and cost effective ground source heat pump installations.

For example, recently a subway station that was permanently pumping away the flow of natural ground water through a large sump realised that the diverted flow of water from the sump through a heat exchanger could supply enough flow to a ground source heat pump, providing heating and hot water to the subway station offices.

Having a clear understanding of your energy source options and how to apply them could be the difference between winning and losing a job.  Think outside the box and if in any doubt speak to your manufacturers.


2. Application

GSHP’s are traditionally used for heating and hot water in domestic buildings. However awareness of their flexible applications and heat sources have opened up new emerging markets, including holiday parks, lodges, forest retreats, care homes, B&B’s, schools, hospitals, golf clubs, farms, offices, lighthouses, house boats, boat sheds, swimming pools, green houses, wood drying facilities, subway stations, community centres, sports centres – as you can see, the list goes on! The Non Domestic Renewable Heat Incentive (RHI) allows uses of the generated heat for some industrial practices as well.


3. District Heating

In addition to commercial applications, new build installations and, significantly, district retrofit installations are also able to access generous payments for 20 years through the Non Domestic RHI. District systems replacing electric heating in existing housing stock are also able to tap into capital subsidy support through the Energy Company Obligation (ECO).

District heating provides each home with its own ground source heat pump, ensuring heating and hot water independence. The heat network is created by linking multiple properties to a communal ground array, designed to deliver an efficient, reliable and durable source of heat for the life of the property. This system overcomes the need for a central plant, the efficiency is not compromised by heat loss from distribution pipework, and there is no need to meter and apportion energy bills between dwellings – avoiding the need to comply with Heat Network (Metering & Billing) Regulations 2014.

The key to district and getting the Non Domestic RHI for non-commercial properties is that each property heated by the ground source system must have its own EPC – opening up a wealth of opportunities from flats to large sprawling estates.


4. Location

Some ground source heat pumps can be bulky units which take up space in a utility room or kitchen. It’s entirely possible to site a heat pump outdoors, as long as you can provide a weatherproof enclosure.  This can be a good way to maximise space indoors, and eliminate nuisance noise.

Smaller units on the market are designed to be installed inside the property, typically in a kitchen or airing cupboard, and are exceptionally quiet, such as Kensa Heat Pumps’ Shoebox range.


5. Controls are easy

Much like a boiler, you can use traditional controls with a heat pump. The controls that come with your underfloor heating can be easily integrated as well, so you can go from traditional and simple, right through to advanced touch-screen controls. Pick a control type that suits the end user’s needs and abilities.

Once the heat pump is commissioned and correctly set up, it should be a matter of “fit and forget” – the end user shouldn’t need to change any of the settings on the heat pump, and any adjustments for comfort or timing can be made using the proprietary control system.  Some people have the idea that using a heat pump is complicated and confusing – it shouldn’t be!


6. But – it’s not a boiler

It can be tempting to explain heat pumps as just another heat source, “just like a boiler”. That’s fine for explaining in basic terms, but for the installer, it’s worth remembering that there are a few differences.

The lower flow temperatures involved mean that a bit of forward thinking is needed when specifying a system, especially for retrofits.

System design is vitally important. Really.

This point cannot be stressed enough! It’s such a big part of installing a heat pump.


7. Get the heat emitter sizing correct.

Remember that those lower flow temperatures do make a difference to how big the radiators need to be, or how tight the pipework spacing should be in your underfloor system.

Room by room heat losses have got to be done in order for your installation to qualify for MCS approval, so make use of them to size your emitters!  Sometimes installers who are new to heat pumps after fitting gas or oil boilers for years struggle with getting used to going into this much detail. If you have an underfloor specialist doing a design for you, try to get them to work from the heat loss calculations, rather than making assumptions. By the time the underfloor system is in, it’s too late to change it.

You will almost certainly require a buffer tank, unless you can guarantee that 25% of the system volume is left uncontrolled (i.e. no zone valves or actuators).

Your hot water cylinder needs to be specified to account for that lower flow temperature as well. The surface area required to transfer heat will be bigger than a standard unvented cylinder’s coil. Some manufacturers use “tank in tank” cylinders, which is one way to overcome this issue. Alternatively, look at heat-pump-specific cylinders – make sure the coil size is appropriate though, and not only that, check that the coil diameter and tapping sizes are OK, especially for larger output heat pumps.


8. High temp DHW is possible

For a long time, heat pumps just weren’t especially good at handling hot water demands because they didn’t generate very high temperatures to start off with.

For some, this meant reliance on direct electric heating to “top up” whatever the heat pump could provide – defeating the object of using a heat pump to begin with.

Luckily progress has meant that using different types of refrigerant within the compressor allows higher temperatures to be achieved. High temperature heat pumps are increasingly common, and can provide flow temperatures high enough that you can even do away with legionella prevention routines in the hot water cylinder. No more immersion heaters required!


9. Maintenance

There aren’t many serviceable parts in a heat pump. They actually need very little in the way of servicing; just a check over once a year, making sure the pressure in the heating system and the ground loops is as it should be, and that the antifreeze is at the right concentration.  Clear out any strainers fitted to the ground array and if there’s a filter on the heating system, check that too.  Of course, an unvented cylinder should be checked annually too, so you can always kill two birds with one stone and do this check at the same time.


10. The RHI is here to stay

The RHI has helped to widen the heat pump market in the UK. But householders remain sceptical because they worry that the funding rug will be pulled from under their feet. After seeing solar PV and biomass hit their tariff degression points comparatively quickly, end users are asking if and when it could happen for heat pumps.  The answer is “it’s miles off”! Due to the spike in installs for PV and biomass because of their former high tariffs, the sales of heat pumps compared to other renewable technologies are that much lower and far from the degression points that it seems extremely unlikely that a degression would be triggered in the near future.

But what if the Government make cuts, or withdraw the RHI altogether? Again, this is unlikely – the RHI is enshrined in law, so the funding for it is “ring-fenced”.

As you can see, ground source heat pumps offer diverse, endless opportunities. Their flexible applications and ranges of heat sources make them one of the most dynamic and adaptable heating technologies. Getting to grips with ground source needn’t be scary, and to help, most manufacturers offer dedicated training and support services to assist you.

For further technical assistance, visit Kensa’s comprehensive Knowledge Hub online at

For further technical assistance:

Visit Kensa’s comprehensive Knowledge Hub online at

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