Alpha common fault and error codes

Alpha common fault and error codes

Alpha boilers, like other brands, use fault and error codes to indicate specific problems within the system. These codes help in diagnosing issues, facilitating quicker repairs. Below are some common Alpha boiler fault and error codes and their typical meanings:

  1. E10: Overheat – This code indicates that the boiler has exceeded its safe operating temperature, potentially due to a blockage in the system or a failure in the pump or thermostat.
  2. E20: High-Pressure Fault – This error is shown when the system pressure is too high, which could be due to overfilling or an expansion vessel issue.
  3. E25: Dry Fire – The E25 code signifies that the boiler attempted to fire without detecting water in the system, indicating a potential issue with the flow sensor or low system pressure.
  4. E28: Flue Fault – This code appears when there is a problem detected with the flue system, possibly due to blockages or incorrect installation.
  5. E34: System Pressure Too Low – Similar to the E10 code but specific to low pressure, this indicates the system pressure has fallen below the minimum required for safe operation, often due to leaks or bleeding radiators.
  6. E50: Domestic Hot Water (DHW) Sensor Fault – Indicates an issue with the sensor monitoring the temperature of the domestic hot water, which could affect hot water delivery.
  7. E60: Fan Fault – This error code signifies a problem with the boiler’s fan, which is essential for removing exhaust gases and drawing in fresh air for combustion.
  8. E83/E84/E85: PCB Fault – These codes indicate various issues with the Printed Circuit Board (PCB), the central control unit for the boiler, which could lead to a wide range of operational problems.
  9. E90: Pressure Switch Fault – Signifies a problem with the pressure switch, which is essential for monitoring the system’s pressure and ensuring safe operation.

Troubleshooting and Resolution

  • For overheating (E10) and dry fire (E25) errors, check for blockages, ensure adequate water flow, and verify that the pump and thermostat are functioning correctly.
  • High-pressure (E20) and low-pressure (E34) issues can often be resolved by adjusting the system pressure, either by filling the system or releasing excess water.
  • Flue faults (E28) require inspection of the flue for blockages or installation issues. Ensure the flue is clear and correctly fitted.
  • DHW sensor faults (E50) and fan faults (E60) may involve checking the respective components for damage or failure and replacing them if necessary.
  • PCB faults (E83/E84/E85) and pressure switch faults (E90) are complex and typically require diagnosis and repair by a qualified technician.


Alpha boiler fault and error codes provide critical information on the system’s status and potential issues. While some basic troubleshooting can be done by homeowners, many of these faults require professional intervention due to their complexity and the technical knowledge needed for repairs. Regular maintenance by a qualified engineer can help prevent these issues and ensure your boiler operates efficiently and safely.