BoilerFaultCodesThe 6 most common faults
Your boiler's internal pump is unable to circulate water around the system, meaning your heating and hot water will not work.
Turn the boiler power off and back on to attempt a resetGently tap the side of the pump casing (if accessible) to dislodge any internal blockagesEnsure your system pressure is topped up to between 1 and 1.5 bar
Your boiler has detected trapped air or a blockage that is preventing water from flowing properly through the heating system.
Check that your boiler pressure is between 1.0 and 1.5 barBleed all radiators in the house to release trapped airEnsure all radiator valves and isolation valves under the boiler are fully open
Your boiler is unable to light the gas to start the heating process, meaning your home and water will not get warm.
Check that your gas emergency control valve is in the 'open' positionIf you have a pre-payment meter, ensure you have sufficient creditPress and hold the reset button for several seconds to try restarting the boiler
Your boiler is struggling to detect a flame, which means it cannot safely stay lit to provide heating or hot water.
Check if other gas appliances (like a hob) are working to ensure your gas supply is activeCheck that your prepaid gas meter has creditHold the reset button for 5 seconds to see if the boiler restarts
Your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.
Check that all radiator valves are fully open to allow water to flow.Ensure there is enough water pressure by checking the gauge is between 1 and 1.5 bar.Press and hold the reset button for several seconds once the boiler has cooled down.
Your boiler is struggling to heat the water quickly enough, which usually means there is a blockage or a pump issue preventing water from circulating properly.
Check that your boiler pressure is between 1 and 1.5 bar on the pressure gaugeEnsure all radiator valves are fully open to allow water to flowTry bleeding your radiators to remove any trapped air
on the Alpha FMK
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 Alpha 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