Viessmann EE Fault

Viessmann EE Fault

The Viessmann EE fault code generally indicates an external fault that has been detected by the boiler’s control system. This external fault might be related to an external control device, such as a thermostat, external energy management system, or sensor that is connected to the boiler but operating outside of its expected parameters or failing to communicate properly.

Causes of the EE Fault Code

  1. Faulty External Thermostat or Sensor: If an external thermostat or sensor connected to the boiler is malfunctioning or improperly installed, it can send incorrect signals to the boiler, leading to the EE fault code.
  2. Wiring Issues: Problems with the wiring connections between the boiler and the external devices can disrupt communication, causing the boiler to register an external fault.
  3. Incompatible External Controls: External control devices that are not compatible with the boiler’s system or incorrectly configured can trigger the EE fault.
  4. External Energy Management System Issues: If the boiler is connected to an external energy management system, any faults or communication errors within this system can result in an EE fault code being displayed on the boiler.

Troubleshooting and Resolving the EE Fault Code

  1. Inspect External Devices: Check any external thermostats, sensors, or control devices connected to the boiler for signs of damage or malfunction. Ensure they are correctly installed and configured according to the manufacturer’s specifications.
  2. Check Wiring Connections: Verify that all wiring connections between the boiler and external devices are secure and in good condition. Look for signs of wear, damage, or loose connections that could affect communication.
  3. Test External Devices: If possible, test external thermostats, sensors, or control devices to ensure they are functioning correctly. This may involve using diagnostic tools or temporarily replacing them with known working units.
  4. Review Device Compatibility: Confirm that all external devices connected to the boiler are compatible with its system. Refer to the boiler’s manual or consult with a Viessmann technician for compatibility information.
  5. Reset the Boiler: After addressing any issues with external devices or connections, reset the boiler to see if the EE fault clears. This can help re-establish proper communication between the boiler and external controls.
  6. Consult a Professional: If the EE fault persists or you’re unable to identify the external issue, it’s advisable to seek assistance from a Gas Safe registered engineer or a Viessmann-certified technician. They can provide a comprehensive diagnosis and resolve complex issues related to external faults.


The Viessmann EE fault code signals an issue with an external device or control connected to the boiler. Addressing this fault involves inspecting and testing external thermostats, sensors, and control devices, as well as ensuring proper wiring and device compatibility. Due to the complexity of diagnosing external faults, professional assistance may be necessary to accurately identify and fix the underlying problem, ensuring the boiler operates efficiently and reliably.