Heat pump servicing and repair

MCS advises a yearly check-up by a professional, and most manufacturers make regular servicing a condition of their warranty. Read the warranty terms in your handover pack before assuming a missed service does not matter.

A heat pump service typically covers the outdoor unit's coil, fan and drainage, the water-side filters and strainers, system pressure and expansion vessels, the condition of the antifreeze where the system uses it, the cylinder's safety devices, electrical connections and the controls. A good engineer also reads the unit's own data: flow temperatures, running hours, defrost cycles and error history.

Between services, keep leaves, snow and plants clear of the outdoor unit. Anything beyond the controls and the area around the unit is for the engineer.

Opening the refrigerant circuit is regulated. Anyone who installs, services, repairs, recovers gas from or decommissions a heat pump containing F gas must hold the right personal qualification; working without it is against the law. Equipment above certain F gas quantities must also be leak-checked at set intervals, and the owner is responsible for making sure that happens. Many domestic monobloc units contain small refrigerant charges in a sealed circuit, and some use propane, which is not an F gas but needs its own safe handling.

Ask any engineer who proposes to open the refrigerant circuit to confirm their F gas certificate, and for propane units, their training on flammable refrigerants.

The most common complaint is high running costs, and the cause is often settings rather than a broken part: a flow temperature set far higher than the design, weather compensation switched off, heating schedules copied from the old boiler, or a hot water cycle running more often than needed. Undersized radiators in one or two rooms can push the whole system to run hot.

A service visit that reviews these settings against the original design can make a bigger difference than any repair. Keep the MCS certificate, heat loss calculation and commissioning record handy so the engineer can compare the current behaviour with what was designed.

Genuine faults include low system pressure from a leak, a blocked strainer, a failed circulation pump, sensor or control board faults, fan damage and, less often, refrigerant problems. Note the make and model, any error code on the controller, when the problem started and whether it affects heating, hot water or both. A photo of the controller screen helps.

If the installation is still under the installer's workmanship warranty, contact the original installer first. If that fails and the installer was MCS certified, MCS has a process for problems with certified installers.

• make, model and age of the heat pump and cylinder
• error codes, and whether heating, hot water or both are affected
• the original installer, if known, and warranty status
• whether the unit contains F gas or propane
• access to the outdoor unit and the plant cupboard

Heat pump engineers in your area see the job description without your name or contact details. Exactly one engineer can buy it, and at that point it disappears for everyone else. The engineer pays for the lead, not you.

We send you the engineer's business name, address and phone number by email before your details are released, and you can withdraw consent at any time. We cannot guarantee a quick callout or that anyone takes the job. Offrano does not assess repair work, so ask about the engineer's experience with your make of heat pump and their F gas qualification.