Common Fault Codes and Winter Freeze Protection

Understanding basic error codes can prevent unnecessary service calls during winter. Most modern gas boilers feature self-diagnostics:
Fan/Flue Fault (often indicated by a specific code): Usually caused by obstructed flue terminals or strong wind gusts; inspect external vents.
Ignition Failure: Check if the gas supply valve is open and if the ignition electrodes are clean.
Overheat Protection: This often signals trapped air in the system or a blocked filter; bleeding radiators may resolve it.
However, the most critical protection is winter freeze prevention. If you plan to leave the property unoccupied for extended periods, do not simply cut off all power, gas, and water. Most boilers have a built-in anti-freeze function that automatically activates the circulation pump and burner when the internal temperature drops below 5°C.
If you disconnect the power entirely, water trapped inside the main heat exchanger and plate-to-plate exchanger can freeze and expand, irreparably cracking the heat exchanger block. This is the most expensive repair a boiler can face. The safest practice is to leave the gas boilers in standby or frost-protection mode with electricity and gas connected, ensuring internal components remain warm and protected.