BoilerFaultCodesThe 6 most common faults
Your boiler has tried to light several times but cannot start, which means you currently have no heating or hot water.
Check that your gas emergency control valve is in the 'on' positionIf you have a pre-payment meter, ensure it has sufficient creditCheck if other gas appliances in your home, such as a hob, are working correctlyGently press the 'Reset' button on the boiler control panel
Your boiler has become too hot and has shut itself down as a safety precaution to prevent internal damage.
Check that the boiler pressure gauge is between 1.0 and 1.5 bar and top up if necessary.Ensure all radiator valves and any isolation valves under the boiler are fully open.Bleed your radiators to remove any trapped air that might be blocking water flow.
Your boiler has shut down because it keeps losing water pressure and needs a top-up or has a leak that needs investigation.
Check the pressure gauge; if it is below 1 bar, use the external filling loop to top up the system to 1.5 bar.Inspect all visible radiators, valves, and pipework for any signs of water leaks.Reset the boiler to clear the code and monitor the pressure gauge for further drops.
Your boiler has started an ignition but the flame has unexpectedly gone out, causing the system to shut down for safety.
Check the outdoor condensate drain pipe for any blockages or ice if it is freezing outside.Inspect the outdoor flue terminal to ensure it is not obstructed by leaves, nests, or debris.Ensure your gas supply is active and, if using LPG, check that the tank is not empty.Reset the boiler once you have checked for external obstructions.
Your boiler has stopped working because the water pressure inside the system is too low.
Locate the external filling loop, which is usually a flexible silver hose connected to the pipework.Slowly open both taps on the filling loop to allow water into the system.Wait for the pressure gauge on the boiler to reach between 1 and 1.5 bar, then close both taps tightly.
Your boiler has been manually reset too many times in a short period and has locked itself out as a safety precaution.
Switch the electricity supply to the boiler off at the fused spur switchWait for 30 secondsSwitch the power back on to clear the temporary lockout
on the Keston Heat 55
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 Keston 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