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Air Source Heat Pump Installation: UK Guide

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Air source heat pumps (ASHPs) are highly beneficial, offering a renewable energy alternative to traditional gas boilers and providing an opportunity for households to reduce energy bills. But heat pumps can be expensive to install, leading some to perhaps consider installing one themselves.

The reality is that air source heat pump installation is not something you should undertake yourself, but it is in your best interest to understand a little about the heat pump process if you’re thinking about moving away from fossil fuels and changing to this method of renewable heating.

Installing An Air Source Heat Pump System – Getting Started

The first key step is finding the best heat pump installers to fit your new air source heat pump, so there will be little stress and your only concern will be learning how to use and get the most out of your new system.

This guide will break down what you can expect when having an air source heat pump installed, especially if replacing an old heating system such as a gas boiler, ensuring you have knowledge about all the stages of the installation process.  

Process For Air Source Heat Pump Installation

  1. Site visit. The installer will visit your home to carry out an onsite inspection to ensure that your home is suitable for an air source heat pump. They’ll be able to help you at this point regarding any eligibility for available grants.
  2. Removal of old heating system. The installer will remove your existing heating system, typically a gas boiler. Your existing pipework and radiators/underfloor heating will be assessed for compatibility and upgraded if necessary.
  3. Air source heat pump units installed. The indoor and outdoor units will be installed, with the outdoor unit (that pulls the heat from the air) being placed in an area with free movement of air to ensure maximum efficiency. Good mounting helps minimise noise and vibration.
  4. Heat pump unit connected to the heat distribution system. This means connecting the outdoor and indoor units via a refrigerant piping system and hooking them up to the hot water cylinder and radiators or underfloor heating. 
  5. Remaining electrical wiring or upgrades.: Your electrical system may need upgrades so that it can handle the extra power needed by the heat pump
  6. Testing phase. The installer will make sure that the air source heat pump functions correctly teach you how to use it correctly.

air source heat pump installation infographic

Why should a professional be installing your air source heat pump?

Installing an air source heat pump requires a certified installer with a thorough understanding of the system components. The professional heat pump engineer should have extensive knowledge in a number of key areas including low-temperature heating systems, vapour compressors, weather compression and heat pump controls, in order that the system can be set up correctly for best performance and maximum energy efficiency.

ASHPs have refrigerant circulated in the compressor and function at low temperatures to optimise their efficiency. They are not devices that can simply be switched on and off like a conventional boiler, so need to be set up correctly to achieve the right level of efficiency and avoid using more electricity than it needs to.

A heat pump has electrical connections that have to be set up by appropriately qualified electricians as well as plumbing circuits that need to be made by unvented system qualified and experienced installers.

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Can you install an air source heat pump yourself?

Installing an air source heat pump is not a job that should be attempted by anybody other than a qualified professional. It is possible that some parts of the pipework could be fitted by a competent DIYer looking to minimise costs, as long as they follow the instruction laid out by the system designer.

It is also possible that insulation on the pipe can also be added by someone with good DIY skills and experience, but you really should seek advice from the right installer before you attempt any of the installations yourself. Luckily, we pair you with some of the UK’s top air source heat pump installers, so you really won’t need to worry about having to install any of it yourself.

Choosing the right type of air-source heat pump

There are two main types of ASHP you may want to consider:

  • Monobloc systems – these have all the refrigeration components sealed in one unit. So, no refrigerant connections are required to be made on-site, meaning the system can be completely installed by a plumber and electrician. The monobloc unit should preferably be less than 10 metres from the hot water cylinder or underfloor heating manifolds.
  • Split type heat pump – if you need the outdoor unit to be further away from your property or you live in an especially cold climate then this type of pump could be more suitable. A split air source heat pump has indoor and outdoor units, with half of the heat pump (with the actual fan in it) outside and half of it inside, and the two halves are linked together with refrigerant pipes on site.

What size air source heat pump do you need for your home?

The most suitable size air source heat pump that you need for your property can be worked out by your installation design engineer who will take into account how much heat your household requires. As with any suitable heat distribution system, the level of heat loss and the hot water requirements of your home needs to be calculated. Additionally, the local weather conditions as well as the design temperature needs of the house are taken into consideration, after which a heat pump will be specifically chosen to cover the load.  

What will your heat pump installer do?

The heating engineer installer will design and detail the equipment involved in the installation including the heating capacity, where the equipment will be sited, the relevant distribution networks, and the user controls. Prior to fitting the system, you will be informed what aspects are not included, such as repairing decoration that might be impacted by an installation, particularly in an existing older property. 

Some installers might also be qualified plumbers and therefore able to include other plumbing aspects that could be affected by the ASHP installation. The installer will get your heat pump system up and running and provide clear instructions for how it works. They are also likely to offer maintenance and aftercare support packages. 

What does an air source heat pump look like when it is installed?

Air source heat pumps are outdoor units, but require a controller and potentially two cylinders as indoor units inside the property. The fan unit, typically 1200mm (h) x 1000mm (w) x 400mm (d), will be connected to at least one hot water cylinder.

An extra cylinder (buffer tank) about a third of the size of the hot water cylinder may also be required. Inside, there will be an ASHP control box.

Also, there will be multiple circulation pumps and pipework, as well as a manifold and control box, if the system is being used to supply an underfloor heating system. This is best located in one room that allows enough space for the materials and pipework, but also for easy access for future maintenance or repairs.

How long does the installation of an air source heat pump take?

Depending on how complex the installation is, an air source heat pump could be installed in one day, but typically two. A ground source heat pump can take several days because of the groundwork excavation required. A solid base for the outdoor unit is required, and needs to be in place prior to the installation. 

In some instances, it may be possible to use some of the existing pipework and radiators, while in other installations, work may be required to the existing property to make it suitable for the air source heat pump. This will add to the time and cost to the installation.

How much does it cost to install a heat pump?

Total installation costs for an air source heat pump in a new or self-build property is expected to be upwards of £11,000. That number will be higher in an older building when you take into account improvements to the home’s fabric and replace and remove existing heating systems. The cost will still be significantly less than ground source heat pumps which are more expensive because of the extensive excavation and groundwork involved with the installation process.

Various government grants schemes aimed at helping households reduce their carbon footprint and energy bills (and improve their Energy Performance Certificate rating), such as the Boiler Upgrade Scheme, can help by providing grants of up to £7,500 towards the cost of heat pump installation. However, even with the grant, some households will still likely have to make a contribution towards the installation costs of a new heat pump.

With an energy efficient system you will start to save money on heating costs, compared to if you were running traditional boilers, and the bill savings will add up over time to cover the costs of installation.

What do you need to know after your air source heat pump has been installed?

When your ASHP has been installed you should not have to get too involved as it will already have been commissioned by the installer. All you need to concern yourself with is ensuring you get a proper handover of the system from the installer so that you fully understand how it works and any potential issues. You should not need to change any of the settings, but should only attempt to do so when you are fully competent. 

Does an air source heat pump need a lot of maintenance?

With most heat pumps, the maintenance and checks are visual. There are inspections that you can do such as checking that the outdoor unit has free air movement and is not blocked up with leaves or other debris.

Also, you should inspect the pipework to make sure all of the insulation is intact and there are no visible signs of leaks or corrosion on the pipework or casing. However, you will still need to service your central heating system that is likely connected to the air source heat pump.

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Ollie Creevy
Ollie has been writing content online about home improvements for over 3 years. With a real interest and in-depth knowledge of heat pumps and ECO home improvement measures you can use to save on your energy bills. Ollie also keeps up to date with all the Government grants available for you to take advantage of like ECO4 and the Boiler Upgrade Scheme.