Viessmann Overheating or Electrical Damage in Thermostat

Thermostat emits a burning smell or becomes unusually hot to the touch.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Incorrect wiring with mains voltage on low‑voltage terminals, Internal short circuit, Overloaded relay contacts, Installation in very hot environment

How to Fix / Troubleshooting

Safety first: Immediately turn off power at the breaker. Do not continue using a thermostat that smells of burning or is excessively hot.

  • Inspect visually: After power is off and the device has cooled, remove the thermostat from the wall and look for signs of melting or charring.
  • Do not reuse damaged unit: If any damage is visible, the thermostat must be replaced.
  • Check wiring scheme: Have a qualified electrician or heating engineer verify that the thermostat is wired only to appropriate low‑voltage or control circuits as specified by Viessmann.
  • Improve ventilation: Ensure the thermostat is not installed above a heat source or in a confined, unventilated space.
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Repair Difficulty

Professional Required 5/5

Required Part

Viessmann smart thermostat
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