How to spot a bad heat pump installation
Short answer
Look for poor drainage, missing pipe insulation, badly supported pipework, very hot exposed pipes, an immersion heater left running, incorrect controls and untidy hydraulic design. None proves the whole system is bad on its own, but several together are a strong reason to ask for an independent inspection or commissioning check.
Last checked 24 September 2026 · 1 source
What should I check outside?
Start with the obvious details.
The outdoor unit should be level and securely mounted. Pipework should be properly insulated, including elbows and joints rather than only the straight sections.
Metal clips should not create unnecessary direct contact with bare hot pipework. Any insulation should be continuous and weather-resistant.
Check how condensate water is handled. Water should not simply collect under the unit if the installation needs a drain, tray, gully or soakaway.
What should I check in the plant room?
Be cautious if hot pipes, valves or cylinder connections are giving off obvious heat into the room.
In the source interview, the installer could not comfortably hold a hand on part of the hot pipework. His view was that exposed heat at that point indicated poor insulation and wasted energy.
Look for insulation with large gaps or makeshift fixing. Cable ties holding poorly fitted insulation are a clue that the finishing detail may have been rushed.
Is the immersion heater supposed to be on?
Not for routine heating in most heat-pump systems.
An immersion heater is effectively direct electric resistance heating. It can be useful for backup, pasteurisation cycles or specific controls, but leaving it running unnecessarily can increase electricity use.
If your bills seem unexpectedly high, check whether the immersion heater is operating more than intended.
What control mistakes should I look for?
One issue from the source inspection was weather compensation apparently being configured without the expected outdoor sensor.
Weather compensation adjusts heating-water temperature as outdoor conditions change. In colder weather the system raises the flow temperature; in milder weather it lowers it.
If the controls are not receiving the information they expect, the system may not run as designed.
Is complicated pipework a bad sign?
Not automatically, but extra hydraulic components should have a clear purpose.
The source installer criticised an unnecessary low-loss header in the inspected system. A low-loss header hydraulically separates parts of the heating circuit. It can be useful in some systems, but unnecessary separation can reduce heat-pump efficiency.
What should I do next?
If several warning signs apply:
- photograph the installation;
- record model numbers and settings;
- ask the installer for the commissioning documents;
- compare the work with manufacturer instructions;
- consider an independent MCS-qualified engineer for a second opinion.
For a new-build home, add the heating system to your snagging list before warranties or builder obligations expire.
Sources
- Source interview with Heat Geek installer, on-site inspection of the new-build heat-pump system.
Last checked: 24 September 2026