The efficiency of most air source heat pumps increases as the water supply temperature is decreased, so to maximise efficiency, reduce running costs and carbon missions, air source heat pump systems are designed to operate at lower flow temperatures. General air source heat pumps pumps circulate heated water up to temperatures of 55°, which is a lower than a conventional gas or oil boiler, so often radiators and and pipework needs to be large enough to provide adequate heat to rooms, which can resiult in additional cost. The type of most appropriate air source heat pump, the size of radiators and existing pipework infrastructure would always be assessed by one of our engineering designers. There are however high temperature air source heat heat pumps that can provide supply water temperatures of up to 110°C. While more expensive than conventional air source heat pumps, there is usualy less requirement to address any radiator or other heat emitter changes.

Underfloor Heating Systems

The lower flow temperatures of most air source heat heat pumps makes them particularly suited for integrating with underfloor heating systems. Underfloor heating systems respond slowly to heating and may take a long time to reach the desired room temperature, however owners do find that they can quickly adapt to the change required to be able to control the system and reach effective heat levels when required. This can make underfloor heating systems well suited to a building that is used frequently during the week due to the lower temperature difference between flow and return pipework than that of conventional heating systems. This means that the flow rate through the pipework will increase in order to provide the same amount of heat. It is important to consider that raising floor levels, changing or replacing them, to accommodate an underfloor heating system installatio may likely need listed building consent due to the impact of the alterations not only to the floor and substrate, but also to changes to skirtings, doors, and steps.

Air source heat pumps use electricity to generate heat, so require a power supply - be it National Grid, solar, CHP or turbine. Domestic sized installations will normally only need a single-phase electrical supply, but larger installations will require a 3-phase supply. (A single phase supply is smaller and most domestic houses with gas central heating need single phase and have this as standard. If you require two or more electricity meters then you need a three phase supply. As we have electrical engineering specialists in house, we would assess all the equipment you will be running and determine how much power you need) Also early engagement with your energy provider would be essential to check that, if a new supply is required, that it can support the electrificaton of heating, as in some rural communities in the UK, this may be challenging where there has not been upgrades to the electricity network (to support heating electrification).

Buffer vessels, which are specifically for low temperature heating systems and not for domestic hot water production, can be added to increase the heating system volume, maximise air source heat pump run times and efficiency, and buffer any discrepancy between the heat pump flow rate and the heating system flow rate. Buffer vessels also have a role in defrost cycles. Buffer vessels are not required in all heating systems, as the management of the minimum system volume has been incorporated within the design of some air source heat pumps.

Water Heating

An air-water air source heat pump can also be used to heat domestic hot water. The heated water is transferred to a hot water cylinder, much the same as with a
conventional indirect hot water system. Domestic hot water has to be stored above 60^oC to prevent Legionella bacterial growth and associated health risks. As most general air source heat pumps provide hot water at 55°C, an internal or external electric immersion is needed to increase the temperature of the water to a safe temperature of 60^oC. Again we would help calculate the consumption patterns so that the air source heat pump is correctly sized to meet the heated water demand. 

Generally, the installation of air source heat pumps are considered permitted development. However, these must comply with conditions listed on the UK Planning Portal website. Similarly the installation of a ground source heat pump or a water source heat pump at domestic premises is usually considered to be permitted development, not requiring planning permission. However consents are likely to be required for installing any type of air source heat pump in a listed building or buildings in a conservation area, scheduled monuments, or installations that affect designated wildlife sites. Installation works need to take into account wildlife, particularly protected species and wildlife licenses may be required. Also there are a range of ecological considerations when it comes to water source heat pumps, and specialist advice should be sought when installing heat pumps.

All heat pump installations have to comply with Building Regulations, and guidance is set out in the Approved Documents. Ground source and water source closed-loop systems generally do not require a permit from the Environment Agency. Where they are installed adjacent to or in a watercourse, consent may be required. Owners are liable for any adverse effects that may be caused by their system (such as a leak that could cause pollutants to enter the groundwater).

For open-loop systems, groundwater investigation consent from the Environment Agency is needed before drilling or test pumping any abstraction boreholes. If work
proceeds, you will require an abstraction licence and a permit to discharge. For further advice, see Open-loop heat pump systems: permits, consents and licences.