Alpha E20 Fault

Alpha E20 Fault

The Alpha E20 error code signifies a high system pressure fault within the boiler. This condition occurs when the water pressure in the heating system exceeds the maximum level recommended by the manufacturer, potentially leading to operational issues or damage to the boiler and its components.

Causes of Alpha E20 Error Code

  1. Overfilling: Adding too much water to the system during topping up can lead to excessive pressure.
  2. Faulty Expansion Vessel: The expansion vessel absorbs excess pressure from heated water. If it’s not functioning correctly, pressure can build up.
  3. Faulty Pressure Relief Valve: This valve releases excess pressure to prevent damage. If it’s malfunctioning, it may not adequately relieve pressure, leading to high readings.
  4. Heating System Issues: Blockages or air in the system can also contribute to abnormal pressure increases.

Troubleshooting and Resolving the Alpha E20 Error Code

  1. Check System Pressure: Verify the pressure gauge reading. The normal operating pressure is usually between 1 and 1.5 bar. Anything significantly higher indicates an issue.
  2. Bleed Radiators: Releasing air from radiators can reduce pressure in the system. This is a simple step that can be performed by the homeowner.
  3. Check for Overfilling: If the system was recently topped up, it might have been overfilled. Some boilers have a pressure release procedure, but proceed with caution and consult the manual or a professional.
  4. Inspect the Expansion Vessel: The expansion vessel should be checked by a professional to ensure it’s functioning correctly. It may need to be repressurized or replaced.
  5. Examine the Pressure Relief Valve: This valve should also be checked by a professional. If it’s faulty, it will need replacing to ensure it can release excess pressure safely.
  6. Seek Professional Help: Given the potential complexity of diagnosing and repairing issues related to high system pressure, it’s advisable to contact a Gas Safe registered engineer. A professional can safely identify and rectify the cause of the E20 error code.
  7. Regular Maintenance: To prevent future occurrences of the E20 error and other operational issues, ensure your boiler and heating system receive regular professional maintenance. This can help identify and address potential problems before they lead to system faults.


The Alpha E20 error code is a critical indicator of high system pressure, necessitating prompt attention to prevent damage to the boiler and ensure efficient operation. While some causes can be addressed by the homeowner, such as bleeding radiators or checking for overfilling, resolving the underlying issue often requires professional intervention. Regular servicing and timely repairs can help maintain the system’s reliability and safety.