BoilerFaultCodesThe 6 most common faults
Your boiler has tried to light several times but cannot establish a steady flame, usually because there is no gas reaching the burner or the ignition sequence is blocked.
Check if other gas appliances in your home, like a hob, are working to confirm your gas supply is active.Ensure your gas meter has credit if you are on a prepaid meter.Check that the white condensate pipe leaving the boiler isn't frozen if it is cold outside.Reset the boiler by following the instructions on the display panel.
Your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.
Check that the boiler pressure gauge is between 1.0 and 1.5 bar.Ensure all radiator valves and internal isolation valves are fully open.Bleed your radiators to remove any trapped air from the system.
Your boiler is having trouble detecting or maintaining the correct water level, which has caused it to stop running for safety.
Check the pressure gauge on the front of the boiler; it should be between 1.0 and 1.5 bar.If the pressure is too low, use the external filling loop valves to top up the system with water.Reset the boiler by turning the control knob to 'Reset' for a few seconds.
Your boiler has shut down because it keeps losing water pressure and has failed to stay topped up four times in a single day.
Check all radiators, valves, and visible pipework for signs of a water leak.Repressurise the system to 1.5 bar using the external filling loop.Reset the boiler to clear the fault code.If the pressure drops again quickly, turn off the boiler and call a professional.
Your boiler is struggling to keep its flame lit, which is often caused by a blocked air pipe, a frozen drain, or an issue with the gas supply.
Check the white plastic condensate pipe outside for ice and pour warm (not boiling) water over it to melt any blockages.Inspect the external flue and air terminals to ensure they aren't blocked by leaves, debris, or snow.If you use LPG, verify that your tank has sufficient fuel remaining.
Your boiler has detected that the water pressure is too low, causing it to stop working for safety.
Locate the filling loop (usually a silver braided hose with small valves) underneath or near the boiler.Slowly open the valve or valves until you hear water entering the system.Watch the pressure gauge and close the valves once the needle reaches between 1.0 and 1.5 bar.
on the Keston Celsius 30
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