Normal Heat Pump Sounds
Heat pumps are not silent appliances. Several noises are completely normal during operation:
- Fan noise: A steady whooshing sound from the outdoor unit’s fan is normal during operation.
- Refrigerant flow: A gentle gurgling or bubbling sound when the system starts or stops.
- Defrost cycle: Occasional hissing, dripping, or slight vibration during the defrost cycle (usually 5–15 minutes, every few hours in cold weather).
- Expansion/contraction: Ticking or clicking sounds from pipework as it expands and contracts with temperature changes.
Warning Noises That Need Attention
- Grinding or scraping: Indicates a problem with the fan blades or motor bearings. Switch off and call an engineer.
- Loud banging or knocking: Could indicate compressor problems or loose components. Requires urgent attention.
- High-pitched squealing: Often indicates a failing motor bearing or refrigerant leak.
- Persistent rattling: Loose panels, bolts, or debris caught in the fan.
- Vibration transmitted to walls: Poorly mounted unit or worn anti-vibration mounts.
Noise Regulations for Heat Pumps
Heat pumps installed as permitted developments in England must not exceed 42 dB(A) at 1 metre from a neighbour’s window or door. Most modern units produce 40–48 dB(A) at 1 metre distance. If noise is a concern, speak to an installer about positioning and acoustic screening.
Reducing Heat Pump Noise
If your heat pump is louder than expected:
- Check and tighten any loose panels
- Ensure the unit is level
- Check anti-vibration mounts
- Ensure adequate clearance
An annual service includes checking all these points.
Sources: Planning Portal and Microgeneration Certification Scheme.
