BoilerFaultCodesThe 6 most common faults
Your boiler has failed to light, likely because the fuel supply is interrupted or the ignition system cannot spark safely.
Check if your gas supply is turned on at the meterIf you have a prepaid gas meter, ensure it has sufficient creditPress and hold the 'Reset' button for five secondsCheck if other gas appliances in your home, like a hob, are working
Your boiler has failed to light the flame, which means it cannot provide any heating or hot water for your home.
Check if your gas supply is turned on and other gas appliances are workingPress and hold the Reset button for 2 to 3 seconds.Ensure your pre-paid gas meter has credit, if applicable.
Your boiler has overheated, prompting a safety switch to shut the system down to prevent damage.
Allow the boiler to cool down for at least 20 minutesCheck that your radiator valves are open and not blockedTurn the selector switch to the 'Reset' position for a few seconds and then back to 'ON'
Your boiler has detected that there is not enough water flowing through the system to operate safely.
Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.If the pressure is low, use the filling loop underneath the boiler to top it up.Ensure all radiator valves and isolation valves are fully open.Reset the boiler by turning the selector switch to the 'R' position for a few seconds.
Your boiler has detected that water isn't moving through the system properly, causing it to overheat and lock itself for protection.
Check the pressure gauge is between 1.0 and 1.5 bar; top up using the filling loop if it is too low.Ensure all radiator valves and internal isolation valves are fully open.Wait 15 minutes for the safety timer to expire and then press ‘Reset’.
Your boiler has shut down because it grew too hot while trying to heat your water, usually due to poor water flow through the system.
Check that all radiator valves are fully openEnsure your boiler pressure is between 1.0 and 1.5 barReset the boiler by turning the control knob to 'R' for five seconds
on the Biasi ActivA 18S
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Biasi shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue