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Air Source Heat Pump Installation Guide

How to install an air source heat pump

Installing an air source heat pump is not something you should undertake yourself, but it is in your best interest to know the process if you’re thinking about changing to this method of renewable heating. The first key step is finding the best installers to fit your new pump, so there will be little stress or anything else you will need to do except learning how to use your new system. This guide will break down what you can expect when having an air source heat pump installed, which will help you stay informed at every stage of the process.

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

Fitting an air source heat pump (ASHP) takes a fundamental understanding of low-temperature heating systems, vapour compression cycle principles, weather compression controls, and the behavioural characteristics of the heat pump controls is needed to specify the system correctly and set up the right operating conditions of the heat pump.
ASHPs have a refrigerant vapour compression cycle and function at low temperatures to optimise their efficiency. There are several factors that contribute to and influence the efficiency and air source heat pumps are not devices that can simply be turned on and off like traditional boilers. All of the working settings need to be set up or the technology might not achieve the desired results or alternatively could use significantly more electricity.
This heat pump will have 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. Due to the low flow temperatures associated with air source heat pumps the emitters will also have to be specifically sized and controlled to optimise the system.

Can you install an air source heat pump yourself?

Installing an air source heat pump is not a job that should be attempted by yourself. When the system has been designed, then there may be some parts of the pipework that could be fitted by a competent DIYer. The insulation on the pipe can also be added by someone with good DIY skills and experience but you would have to ensure that you get complete guidance from a qualified engineer before you attempt any of the installations yourself.
Luckily, we don’t just offer Government backed heat pump grants but we also pair you with some of the UK’s top heat pump installers, so you won’t need to worry about installing 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 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. The level of heat loss and the hot water requirements of your home is calculated, which takes into consideration the local weather conditions as well as the design temperature needs of the house, and the heat pump is then specified to cover the load.

What will your heat pump installer do?

The installer will design and detail the equipment involved in the installation including the heating capacity, location of the equipment, distribution networks, and the user interfaces like thermostats. Also, they will physically fit the system and tell you what is not included (particularly in an existing older property where things like repairing decoration work are not normally included).
Some installers are also qualified plumbers and might include other sanitary and plumbing installation works within their contract. The installer will also commission the ASHP system and give the homeowner a handover and provide clear instructions for how it works. They could also offer a maintenance package and aftercare support.

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

An ASHP unit is sited outside the home, and you need a controller and potentially two cylinders inside. The fan unit, which is typically about 1200mm tall, 1000mm wide, and around 400mm deep, will be connected to at least one hot water cylinder which is roughly 600mm wide by about 1600mm tall.
There might be an extra cylinder (buffer tank or low loss header) about a third of the size of the hot water cylinder. Inside, there will be an ASHP control box which is about 400mm x 400mm x 100mm deep. Also, there will be multiple circulation pumps and pipework, as well as a manifold and control box for any underfloor heating.
This is best positioned in a plant room that allows enough space for the materials and pipework, but also for any engineer to complete future maintenance or repairs. By putting it all together it is easier for the engineer to get a view of all the components in one place and understand the circuits and controls.

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

Depending on how complex the work is, an air source heat pump could be installed in as little as one day. Normally, the preparation work like building a solid base for the outdoor unit to stand on would have to be in place prior to the installation date.

How much does it cost to install a heat pump?

The cost of installing 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.

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 do much as the system will have been commissioned by the installer. The installer should pass over the system to you and clearly explain how it works and only permit you to change settings that you are completely competent to do.

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

The majority of the time, the maintenance of air source heat pump systems is visual. There are inspections that you can do like checking 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 an annual service on your central heating system that might also be directly connected to the air source heat pump. 

Clive Whyte

I'm Clive, a sustainability advocate and green energy expert. I have over 25 years of industry experience and now I spend my time sharing my knowledge online with the hope of educating Britain towards a more sustainable future.