Thermostat emits a buzzing or humming noise, especially when switching.

Safety: Disconnect power before removing the thermostat.

• Step 1 – Check mounting:
  • Ensure the thermostat is firmly attached to the wall plate and the wall plate is secure.
• Step 2 – Listen for source:
  • Identify if noise occurs only during switching (relay) or continuously (transformer).
• Step 3 – Verify supply voltage:
  • Measure supply voltage to ensure it is within the specified range.
• Step 4 – Replace thermostat if noise is excessive:
  • Persistent loud buzzing indicates a failing relay or transformer.
  • Install a new Protherm smart thermostat.