BoilerFaultCodesThe 6 most common faults
Your boiler has sensed that water isn't moving through the system properly and has shut down to prevent the unit from overheating.
Check that your system pressure is between 1.0 and 1.5 bar on the pressure gauge.Ensure all radiator valves and external isolation valves are fully open.Listen for air trapped in the pump or radiators and bleed them if necessary.Reset the boiler to see if the error clears once water flow is restored.
Your boiler has detected that the water pressure is either too low or too high, causing it to shut down 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 below 1.0, use the filling loop (usually two blue levers or a pull-down lever) to top it up slowly.If the pressure is above 3.0, you may need to bleed a radiator to release the excess pressure.Reset the boiler once the pressure is within the correct range.
Your boiler has shut down because the internal water temperature has become too high, often caused by a lack of water flow or a circulation error.
Check that your boiler pressure is between 1.0 and 1.5 barEnsure all radiator valves are fully open to allow water flowCheck for any frozen external condensate pipes if it is winterTry resetting the boiler via the 'R' or reset button
Your boiler has tried to light itself five times and failed, resulting in a lockout to prevent unburned gas from building up.
Check that your credit or prepaid gas meter has enough credit.Verify that other gas appliances in your home, like a hob, are currently working.Ensure your condensate pipe (the plastic pipe leading outside) isn't frozen if it is currently winter.Press the 'Reset' button on the boiler control panel once.
Your boiler has shut down because there is too much water pressure in the system, which puts unnecessary stress on the internal components.
Locate a radiator bleed valve and use a radiator key to carefully release a small amount of water into a container.Monitor the pressure gauge on the boiler control panel until it drops back into the green zone (typically between 1.0 and 1.5 bar).Ensure the filling loop valves are fully closed to prevent more water from entering the system.
Your boiler has lost its connection with the temperature sensor that monitors the water leaving the unit, meaning it cannot safely regulate heat.
Full guide for 20on the Atag iC28
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 Atag 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
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
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