Advice for maintaining and servicing air source heat pumps – a guide for engineers

Maintaining air source heat pumps is simple but important

In this blog, Steve Ellison, Grant UK’s Assistant Training Manager, shares some useful pointers for maintaining and servicing air source heat pumps to provide installers and engineers with a summary guide about the importance of regularly looking after heat pump systems.

Optimal heat pump efficiency is achieved not only through correct system design, installation and system set-up but also as a result of regular servicing and preventative maintenance checks. Here, we will talk through some of the key areas relating to heat pump servicing and maintenance with the aim of giving heat pump service engineers a useful overview of the steps involved in annual servicing as well as highlighting how regular preventative maintenance can help ensure the longevity of air source heat pumps and aid their performance and reliability year after year.

Important Note – the servicing and maintenance of an air source heat pump system should only be carried out by a competent heating engineer and in line with the servicing instructions supplied in the Installation & Servicing Manual.

Importance of regular maintenance

Grant UK recommends that their Aerona³ air source heat pumps are serviced on an annual basis to help ensure the long and efficient operation of the unit. This is also required to maintain the product’s manufacturer’s guarantee. Also, if the end-user is receiving RHI payments, annual servicing is a mandatory requirement in order to continue receiving such payments. Annual heat pump servicing and maintenance is also important as it gives the customer greater confidence and peace of mind that their heat pump system is performing at its best.

A typical heat pump service will involve the following steps and we will take a closer look at some of these later on in the blog:

  • Visual checks of the heat pump and core components to identify any obstructions and to assess their condition
  • Clean the heat pump evaporator
  • Check the wider heating system including the expansion vessel, system pressure, concentration levels of the anti-freeze/corrosion protection, check the controls settings and look for any leaks on the system.

Cleaning & maintaining a heat pump system

A significant part of looking after a heat pump system is carrying out visual checks on the heat pump itself. As we explain in our Top 5 Tips for looking after a heat pump blog, homeowners should be encouraged to periodically check their heat pump and carefully remove any obstructions and debris from the evaporator and fan outlet that could restrict airflow both through and around the unit, which if not removed could affect the heat pump’s performance. During a service, engineers should carry out a visual check of the heat pump to confirm the condition of the unit. They should also ensure the condensate drain opening in the base of the unit is clear and free of any blockages, check the condition of the flexible hoses and connection points, check the condition of all pipe insulation and ensure that all the required remote controller settings are correctly set.

The heat pump evaporator fins should also be cleaned as part of the service as this helps maintain a good airflow through the heat pump. Any dirt or debris on the fins should be carefully removed using either a soft brush or by gently vacuuming them. The evaporator should also be washed with a neutral cleaner using a low-pressure spray.

Checking the refrigerant & wider heating system

As part of a heat pump service, engineers should check for any signs of leakages from the refrigerant circuit – for example, oil residue on the refrigerant circuit may indicate a refrigerant leak. It is important to rectify any leaks, such as in the refrigerant circuit, because they will impact the heat pump system’s ability to operate at its highest efficiency. It is very important to stress here that under no circumstances should the refrigerant be vented from the charging points on the refrigerant circuit of the heat pump and if any work is required to be carried out on the refrigerant circuit, it must only be undertaken by a F-Gas Registered Engineer.

In addition to checking the refrigerant circuit for signs of leaks, engineers should also complete a thorough check of the heating and hot water system. This will involve checking the expansion vessel pressures and repressurising (if required), checking the operation of the pressure relief valves, cleaning the magnetic filter, checking the heating system pressure and topping up if required, checking the heating and hot water control settings, inspecting the electrical connections and PCB for scorching or dry cables, and checking for the correct concentration and condition of the inhibitor/anti-freeze protection within the system.

To help G1 Installers complete the steps involved in a heat pump service, we have made a PDF Servicing Sheet available to download from the G1 Portal – visit the Downloads section of the Portal to view this useful resource.


If a fault is detected with the air source heat pump, a red LED will flash on the ON/OFF button of the Aerona³ remote controller and a warning icon and error code will display on both the remote controller LCD screen and on the Terminal PCB digital display. To assist with troubleshooting, there is a dedicated section included within the Aerona³ Installation and Servicing Manual that engineers can refer to for Fault Finding assistance. We also have a useful YouTube video which talks through the main icons and displays of the remote controller which you can view here.

Training from Grant UK

If you are interested in learning more about looking after an air source heat pump system, this topic is covered in detail in the Aerona³ air source heat pump product training course that we run at the Grant UK Training Academy. During the course, we talk through how to service a heat pump correctly with the opportunity for engineers to gain hands-on experience working with our range of Aerona³ air source heat pumps. If you are interested in enrolling on this course, please sign up for our training here.

To summarise…

Hopefully this blog has provided a useful introduction to the importance of regular preventative maintenance for air source heat pumps, as well as outlining the key steps involved in an annual heat pump service. Whenever carrying out a heat pump service, engineers must follow the guidelines provided in the relevant Installation and Servicing Manual and, for Grant heat pumps, this can be downloaded either from our website or via the Grant TechBox app.

For further information about air source heat pump servicing, either on the Aerona³ heat pump product training course or on the OFTEC OFT21-504A (Installation, commissioning and servicing of ASHPs) course, please visit our course catalogue here.

Return to top