Heat Pump Making Noise? Common Sounds Explained

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, and ensure adequate clearance. An annual service includes checking all these points.