Atlantic water heater makes a humming or buzzing noise from the top module (heat pump models) during operation.

Safety: Disconnect power before tightening any components. Do not touch refrigerant pipes when hot.

• Check that the heater is installed on a solid, level surface. Add anti-vibration pads under the feet if necessary.
• Remove the top cover and inspect the compressor mounting bolts and rubber grommets; tighten bolts gently without crushing the mounts.
• Ensure that refrigerant pipes are not touching the casing; adjust supports or add foam to prevent contact.
• Inspect the fan blade for damage or imbalance; replace the fan assembly if needed.
• Reassemble and test; a low-level hum is normal, but loud rattling indicates remaining vibration points.