Heater vibrates or makes humming/buzzing noises when heating.

Safety: Turn off power before tightening any internal parts.

Steps:

• Check mounting: Inspect the wall brackets and anchor bolts holding the Eldom heater. Tighten any loose fasteners and ensure the wall is solid.
• Inspect covers: Tighten screws on plastic covers and metal panels that may vibrate.
• Check element position: If the heater was serviced recently, remove the flange and ensure the heating element is not bent against the tank wall.
• Electrical hum: A slight hum from relays or contactors is normal; loud buzzing may indicate a failing relay on the control PCB, which should be replaced.