Vokera AL Series Error codes

Vokera AL Series Error codes

The Vokèra AL series error codes, including AL10, AL20, AL21, AL26, AL28, and AL34, are associated with various issues related to boiler overheating, flow, and return thermistor faults. These codes indicate that the boiler has detected conditions or faults that prevent it from operating safely and efficiently. Understanding these codes can help in diagnosing and resolving issues that may affect your boiler’s performance.

Vokèra AL Series Error Codes Explained

  • AL10: Dry Fire – This error occurs when the boiler fires without detecting water flow, indicating a potential issue with the water circulation system or the flow sensor.
  • AL20: Boiler Overheat – Indicates that the boiler water has exceeded safe temperature limits, potentially due to a faulty thermostat, pump failure, or restricted water flow.
  • AL21: Flue Overheat – This code is triggered when the flue gas temperature exceeds safe limits, possibly due to flue blockages or heat exchanger issues.
  • AL26: Fan Fault – Suggests a problem with the boiler’s fan, which is essential for venting exhaust gases and drawing in air for combustion.
  • AL28: Low Water Pressure – Indicates that the water pressure in the system is below the minimum required level, often due to leaks or natural pressure loss.
  • AL34: Flow Thermistor Fault – Points to an issue with the sensor that measures the temperature of the water leaving the boiler, affecting temperature regulation.

Troubleshooting and Resolving the Issues

  1. AL10 (Dry Fire): Check for proper water circulation in the system. Ensure the pump is operational and there are no blockages restricting water flow. Inspect the flow sensor for faults.
  2. AL20 (Boiler Overheat) & AL21 (Flue Overheat): Inspect the thermostat and pump for proper operation. Clear any blockages in the flue and check the heat exchanger for restrictions or damage.
  3. AL26 (Fan Fault): Verify the fan’s operation and ensure there are no obstructions affecting its performance. Electrical connections should also be checked.
  4. AL28 (Low Water Pressure): Re-pressurize the system if necessary and check for leaks. Ensure the pressure relief valve is functioning correctly.
  5. AL34 (Flow Thermistor Fault): Inspect the flow thermistor for damage or incorrect readings. Check its wiring and connections for faults.

General Advice

  • Reset the Boiler: After addressing potential causes, try resetting the boiler to clear the error codes and reattempt operation.
  • Professional Help: Due to the complexity of these issues, especially when involving electrical components, sensors, or the heat exchanger, consulting a Gas Safe registered engineer is advisable. A professional can accurately diagnose and repair the underlying causes of these error codes.
  • Regular Maintenance: Regular professional maintenance can help prevent these issues by ensuring that all components of the boiler system are in good working order and operating efficiently.


The Vokèra AL series error codes cover a range of issues related to overheating, water circulation, and sensor faults. Prompt attention to these codes is crucial for maintaining the safety and efficiency of your boiler. While some preliminary checks can be performed by homeowners, many of these issues require professional diagnosis and repair to resolve effectively and safely. Regular maintenance is essential for preventing such problems and ensuring the longevity of your boiler system.