Air source heat pump servicing: what a good visit includes

Air source heat pump servicing means inspecting, cleaning and testing the parts that affect safe, efficient operation. It normally includes the outdoor unit, indoor hydraulics, controls and system performance, but it is not a blanket gas-style service with a standard combustion check. A good engineer should assess how your complete heating system is working and explain any findings clearly.

Outdoor unit checks

The outdoor unit is exposed to rain, wind, leaves and airborne debris throughout the year. In coastal or damp parts of Sussex, salt-laden air and moisture can accelerate coil debris and corrosion, so regular checks matter rather than being treated as an optional extra.

The engineer should inspect the coil condition and remove suitable debris without damaging the delicate fins. They should also check that the fan is clean, secure and free to rotate, with adequate clearance around the unit for airflow. A blocked grille, overgrown planting or stored items nearby can reduce efficiency and increase noise.

• Inspect the heat exchanger coil, casing, fan and fixings

• Check air intake and discharge clearance

• Inspect condensate drainage for blockages, damage or poor fall

• Look for corrosion, unusual noise, vibration or signs of water ingress

Condensate drainage deserves particular attention because freezing, blockages or an incorrect route can cause faults and local water damage. The service should also include a visual check of pipe insulation, electrical connections and visible refrigerant pipework, with any concerns recorded for further investigation.

Indoor hydraulics and water-side components

Inside the property, servicing should cover the parts that move and condition heating water. This includes checking system pressure, verifying flow and return temperatures, and confirming that pumps, valves and safety components are operating as expected. Readings should be interpreted in relation to your system design, not simply marked as pass or fail.

Filters and strainers can collect sludge or debris, restricting flow through the heat pump. A good visit includes cleaning them where appropriate and checking for evidence of corrosion, magnetite or repeated contamination. If your system uses glycol or antifreeze, the engineer should check its condition and concentration, where applicable, because weak or degraded glycol may not protect the system as intended.

Sensor checks are also important. Temperature sensors should be secure, correctly positioned and producing sensible readings. Faulty or poorly fitted sensors can lead to poor comfort, excessive cycling or unnecessary use of the immersion heater, even when the heat pump itself appears to be running.

Controls, settings and operating history

Heat pumps work best when their controls are set for steady, low-temperature heating. The engineer should review the weather compensation curve, heating flow temperature, hot water settings, schedules and any room or cylinder sensors. Settings should be explained in plain language and adjusted only when there is a clear reason to do so.

A quality service also involves reviewing cycling and defrost history where the system provides that information. Frequent starts and stops, unusually long defrost periods or repeated backup heater use can point to incorrect settings, restricted flow, poor sizing or another issue that a quick visual inspection would miss.

System performance verification

Servicing should finish with evidence that the system is performing properly. The engineer may record flow and return temperatures, pressure, flow rate, outdoor temperature and relevant electrical or heat output readings. These checks help show whether the heat pump is transferring heat effectively and whether emitters are receiving suitable flow.

It is reasonable to ask how the readings compare with expected operation and whether the system is meeting your comfort requirements. A conscientious engineer will distinguish between routine maintenance, recommended improvements and faults that need a separate repair or diagnostic visit.

Questions to ask before you book

Before arranging an appointment, ask what the service includes and whether the engineer works on your make and model. You can also ask whether they check glycol, filters, sensors, weather compensation and operating history, rather than only cleaning the outdoor casing.

It is useful to confirm whether the price covers written findings and minor cleaning, and whether any remedial work will be quoted separately. Be cautious of vague promises that every heat pump receives the same service, since system design and manufacturer requirements vary.

What you should receive afterwards

After a worthwhile visit, you should receive written findings that record the main checks, relevant readings and the condition of important components. This gives you a useful maintenance history and makes it easier to spot recurring issues over time.

The report should also set out recommendations and next steps, including which items are urgent, which can be monitored and whether a separate repair or improvement is advisable. Clear communication is a strong sign that the service has been carried out with care rather than as a commodity tick-box exercise.