Heat Pump Making Strange Noises
Check the steps below first — if you're not confident, get it fixed safely today.
Post a job — we'll find you an engineer →Do not attempt to open or access the refrigerant circuit of a heat pump — it contains pressurised refrigerant gas and requires an F-Gas qualified engineer to work on.
Heat pump noise is one of the most common concerns for new owners. Many heat pump sounds are completely normal — the fan, the defrost cycle, and refrigerant flow all make noise. However, unusual new noises can indicate a developing fault.
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Most likely cause & what to check
Identify the type of noise and when it occurs. A regular low hum (the fan) is normal. Clicking at startup and shutdown is normal. Dripping and gurgling during defrost is normal — this happens for 5–15 minutes every 1–3 hours in cold weather.
A rattling or vibrating noise that has developed recently suggests a loose panel, fan blade, or mounting bolt. Check all visible screws and fixings on the outer casing. If the unit is not on anti-vibration pads or mounts, fitting these (£20–50 per set) significantly reduces structural vibration.
A high-pitched whining or screeching suggests fan bearing wear — particularly common in units 5+ years old. This requires a heat pump engineer to replace the fan motor (£200–400 for parts and labour).
Loud banging or thumping from the outdoor unit suggests a refrigerant flow restriction, a failing compressor, or loose internal components — call your heat pump manufacturer or MCS installer.
Check that the outdoor unit is not obstructed — leaves, garden debris, or ice can cause the fan to rattle or vibrate. Clear any debris from around and above the unit, maintaining at least 300mm clearance on all sides.
If the indoor unit (the buffer tank or air handler, if fitted) is making gurgling or knocking sounds, there may be air in the heating circuit — bleed the system at the highest points.
Heat pumps are generally louder in heating mode than cooling mode, and louder in very cold weather when the compressor works harder. If the noise seems acceptable to you but concerns neighbours, acoustic screening (garden walls, shrubs) can reduce perceived noise significantly.
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