BoilerFaultCodes
The most common Atag faults
Your boiler has detected that the water pressure inside the system is far too high, causing it to shut down for safety.
Why it happens: This fault occurs when there is too much water forced into your heating system, often because the filling loop valves have been left slightly open or have developed a leak. It can also be caused by a failure in the expansion vessel, which is the internal part responsible for managing the natural pressure changes that happen when water gets hot.
Check that the internal or external filling loop valves are tightly closed.Bleed water from a radiator using a bleed key to reduce the system pressure.Monitor the pressure gauge until it returns to between 1.0 and 1.5 bar.Press the reset button to restart the boiler.
Your boiler has detected that the water pressure is too low for it to operate safely, or it is struggling to move water through the system.
Why it happens: This fault occurs when the boiler's internal sensors detect that the system lacks the minimum water pressure required to circulate heat safely. The most common reason is a slow leak somewhere in the pipework or radiators, but it can also be triggered if the pump has failed and can no longer push water through the heat exchanger.
Check the pressure gauge on the front of the boiler; it should ideally be between 1.2 and 1.5 bar.Locate the filling loop (usually a silver braided hose with small black lever valves) underneath the boiler.Slowly open the valves to let water in until the gauge reaches 1.5 bar, then ensure they are closed tightly.Press the Reset button on the control panel to clear the fault.
Your boiler has detected that the water pressure in your heating system is too high and has shut itself down to prevent damage.
Locate a radiator in your home, preferably one upstairs.Use a radiator bleed key to slowly open the bleed valve over a cloth.Release a small amount of water until the pressure gauge on the front of the boiler drops to between 1.0 and 1.5 bar.Tighten the bleed valve and check the boiler display.
Your boiler has failed to ignite and cannot produce heating or hot water, likely because it has tried to light several times without success.
Check if other gas appliances, like a gas hob, are working to ensure your gas supply is active.If you have a prepaid gas meter, verify that you have enough credit.Press and hold the 'Reset' button on the boiler control panel for several seconds to restart the ignition sequence.
Your boiler has detected an ignition failure or a flame loss, meaning it is unable to stay lit to provide heating or hot water.
Check that your gas prepayment meter has credit (if applicable)Check that other gas appliances, such as a hob, are working to confirm gas supplyPress and hold the 'Reset' button for 2 seconds to see if the boiler restarts
Your boiler has detected an issue with the sensor that monitors water returning from your radiators, which may stop the system from heating effectively.
Check that all radiator valves are fully openEnsure there is enough water pressure in the system (typically 1.0 to 1.5 bar on the gauge)Attempt to reset the boiler using the 'Reset' button
Your boiler is struggling to detect water moving through the system and is currently trying to clear air from the pipes to fix itself.
Check that the boiler pressure is between 1.0 and 1.5 bar on the gauge.Ensure all radiator valves and isolation valves under the boiler are fully open.Gently bleed your radiators to remove any trapped air pockets.
Your boiler is failing to light the gas, meaning it cannot produce any heat or hot water.
Check if other gas appliances, like a hob, are working to ensure gas supply is activeEnsure your gas meter has credit if you use a pre-payment meterPress the Reset button on the boiler control panel once