Viessmann Common Fault and Error Codes

Viessmann Common Fault and Error Codes

Viessmann boilers, known for their efficiency and reliability, also have built-in diagnostic systems that display fault or error codes when the boiler encounters operational issues. These codes help in identifying the nature of the problem quickly. Here are some common fault or error codes for Viessmann boilers and what they typically indicate:

  1. F2: Flame Loss – This error occurs when the boiler’s flame has been extinguished unexpectedly. Causes can include issues with the gas supply, the ignition electrodes, or the flue system.
  2. F4: Flame Signal After Closing – If this fault appears, it means the boiler still detects a flame signal after it was supposed to be extinguished. This could be due to a fault in the flame detector or the control unit.
  3. F5: Repeated Flame Loss – This indicates the boiler has detected the loss of flame multiple times during operation, which might be due to intermittent gas supply issues or problems with the burner.
  4. A1: Pump Dry Run or Low Water Pressure – This code suggests that the boiler is either experiencing low water pressure or the pump is running without water. It’s often resolved by checking the water pressure and refilling the system if necessary.
  5. A2: Flue Gas Temperature Too High – This error code indicates that the flue gas temperature has exceeded safe levels, potentially due to blockages in the flue or insufficient water flow through the boiler.
  6. A3: Boiler Overheating – When the boiler water temperature exceeds the set safety limits, this fault is displayed. It can be caused by scale build-up, low water content, or circulation issues.
  7. A4: Return Temperature Too High – This error occurs if the return water temperature to the boiler is higher than expected, which could be due to poor system circulation or incorrect system design.
  8. A6: Burner Does Not Ignite – This indicates that the boiler’s burner failed to ignite, which could be due to issues with the gas supply, ignition system, or the gas valve.
  9. B1: Coding Fault – This code appears when there is a mismatch in the coding cards or parameters within the boiler’s control unit, requiring reconfiguration or replacement of the coding card.
  10. EE: External Fault – The boiler has detected an external fault, often related to an external control device or sensor connected to the boiler system.

Troubleshooting and Resolution

  • Initial Steps: For many of these fault codes, initial troubleshooting steps include resetting the boiler, checking for obvious issues like gas supply, water pressure, or blocked vents, and ensuring that external controls and thermostats are functioning correctly.
  • Consult the Manual: Each Viessmann boiler comes with a detailed manual that includes a comprehensive list of fault codes and troubleshooting steps. Refer to this manual for specific guidance related to your boiler model.
  • Professional Help: For persistent faults, especially those related to internal components like the burner, pump, or control unit, professional assessment and repair are essential. A Gas Safe registered engineer should be consulted to safely diagnose and resolve the issue.
  • Regular Maintenance: Regular servicing by a qualified professional can help prevent many common issues that lead to fault codes, ensuring your Viessmann boiler operates efficiently and safely over time.