FREQUENTLY ASKED QUESTIONS
Below are answers to some of our most frequently asked questions regarding Heat Pumps. Please select the relevant tab to see the questions for each type of heat pump.
We install three types of heat pumps: Brine to water, air source and exhaust air. Brine to water collects its energy from the ground (boreholes or horizontal loops), then called “ground source” or from water (lake, pond or river), then called “water source”. Air source collects energy from outdoor air and exhaust air collects the energy from indoor air. So what are the pros and cons of the different alternatives?
The main advantage of ground source over air source is that the ground is warmer than the air during the winter when most heating is needed. This makes it possible to obtain better efficiencies (COP’s) with ground source.
Designed and sized correctly, a heat pump system can provide space heating, hot water and cooling for any domestic and commercial property. For existing properties, it is always beneficial to improve insulation, if possible. A review of the heating distribution system on a room-by-room basis is also required to assess if further capacity is needed, for instance more or larger radiators.
No, while underfloor heating is perfect for heat pumps, radiators can work equally well if they are sized correctly. Heat pumps are different from boilers when it comes to the temperature of the hot water that goes into the heating distribution system. While boilers often produce water with a temperature of 70°C, most heat pumps can only produce water up to around 55°C. Furthermore, the lower flow temperatures, the higher the efficiency of the heat pump. Underfloor heating works well with heat pumps as it typically operates with low flow temperatures. In order for radiators to work well with a heat pump, the radiator capacity in each room has to be higher compared to a boiler system. This can be achieved by more radiators, deeper radiators, larger radiators or fan-assisted radiators.
Yes, both indoor and outdoor pools. For outdoor pools used only in the summer, a heat pump system sized for space heating can often do pool heating as well. For ground source heat pumps, the ground collector has to be increased as more heat is drawn from the ground in the summer. (EXCLUDES Air Source Heat Pumps)
For indoor pools, the heating power requirement for the pool room has to be added to the space heating and hot water loads when sizing the heat pump. Usually, an air handling unit is used to control the climate in the pool room and to heat the pool water. It is crucial to select an air handling unit which can operate at low flow temperatures.
A buffer tank adds volume to the heating distribution side of the installation. The purpose is to get a more steady operation and to protect the compressor in the heat pump by reducing the number of starts and stops.
An air source heat pump is expected to last at least 15 years and a ground source heat pump at least 20 years. The ground collector supporting a ground source system will last for many generations of heat pumps.
A heat pump cylinder has an oversize internal coil compared to a standard cylinder. It is required to compensate for the lower flow temperature from a heat pump.
In order determine the right size of the heat pump (in kW) and in the case of ground source, the right size ground collector, we do a room by room heat loss calculation. For new built properties, this is also required for the design of the underfloor heating system and/or radiators.
The physics of heat pumps is the same as that of a fridge or a freezer. In all refrigeration processes, heat is produced as a bi-product. In a heat pump system, the ground (in case of ground source) or outside air (in the case of air source) and the heat produced is used for space heating and hot water in a property.
In most cases, the heat pump is sized to cover the whole heating load of the property and then no back up is required. This is called a monovalent system. A heat pump can also work in tandem with a boiler. This is called a bivalent system. In this case, the boiler is controlled by the heat pump in such a way that the heat pump is the master and the boiler is the slave
Boreholes are always more the more expensive option. Horizontal loops require quite a lot more space. For a new build property, around twice the total floor area and for older properties up to five times the total floor area. In a garden with trees, the available space for collector pipes is reduced as roots have to be avoided. If a paddock or a filed is available, it is usually the best option.
The efficiency of a borehole system is the same as that of a horizontal loop system, provided that the size of the collector is correct.
If passive cooling is required, boreholes are a better option, as the temperature in the borehole is more constant over the year.
Horizontal loops can be either in the form of slinkies; 1 meter wide coils, typically consisting of 350 m of 32 mm pipes stretched over 50 m or straight loops (laid in a similar pattern as underfloor pipes). Sized correctly, both systems can provide enough thermal energy to the heat pump. Straight loops extract heat in a more uniform way, and it is therefore usually Better Planet’s recommendation. Sometimes slinkies can be the best option when trenching is complicated.
We always recommend to lay the pipes at the depth of 1.2 meters. For straight loops, the minimum pipe separation is 1 meter and for slinkies 5 meters.
For our projects, boreholes are drilled between 80 and 150 meters. The depth is related to the local geology and the type of drilling rig. For heat pump sized over 6kW, several boreholes are required and they need to be separated by at least 6 meters.
The installation of a ground source heat pump or a water source heat pump on domestic premises is usually considered to be permitted development, not needing an application for planning permission. If you live in a listed building or a conservation area you should contact your council to check on local requirements.
For a retrofit, the first location to consider would be outside a wall as close as possible to the current boiler location. For a new build, as close as possible to the plant room/installation cupboard. The heat pump needs to be located in a way which allows for a good flow of air through the unit. If placed parallel to a wall, the minimum distance to the wall is 150 mm. A minimum clear distance of 1 meter in front of the heat pump is required. If you consider sitting the heat pump close to an adjacent property, the noise impact has to be assessed. If no suitable location is found next to the property, it is possible to site the unit at a distance from the outside wall. This will require the heat pump to be connected to the property with a high spec pre-insulated pipe buried in a trench.
All air source heat pumps emit a noise. We use heat pump for the manufacturer Nibe for almost all our installations. One of the reasons we like to use Nibe is that the noise level is very low. However, sensitivity to noise is very individual. If you are concerned about the noise, we are happy to take you to an installation and listen to the unit.
You will need a hot water cylinder, a buffer tank (40 or 100 litre depending of the size of heat pump) and two expansion vessels.
The installation of an air source heat pump on domestic premises is considered to be permitted development, not needing an application for planning permission, provided ALL the limits and conditions listed below are met.
These permitted development rights apply to the installation, alteration or replacement of an air source heat pump on a house or block of flats, or within the curtilage (garden or grounds) of a house or block of flats, including on a building within that curtilage. A block of flats must consist wholly of flats (e.g. should not also contain commercial premises). Limits to be met:
The maximum capacity of an exhaust air heat pump is around 5 kW which means that they are mainly used for flats and small bungalows. The system contributes to the ventilation of the property by removing air from kitchens and bathrooms. It is therefore most relevant for new, airtight properties.
All exhaust air heat pumps require ducting. For smaller units, only extract ducting is required while for bigger units both supply and extract ducting is required. In the latter case, the system is effectively a heat pump and MVHR in one system.
The equipment that goes into the property is exactly the same for ground source and water source. The difference is the collection of heat from outside. A water source system collects energy with pipe work in a lake, river, brook, moat or a pond.
If the system collects energy from a moving source of water- e.g. a river, a brook or a pond with an inlet and outlet of water- the efficiency will be higher. If the system collects energy from a pond or a moat without water flowing through, the efficiency depends on the volume of water the pipes are immersed in. If you put too much collector pipes in a small volume of water, it can deep freeze and the efficiency would be lower. This always comes down to design.