BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because it either cannot detect a flame or the internal drainage pipe for waste water is blocked.
Why it happens: This fault occurs when the boiler tries to light but fails to detect a steady flame, causing it to shut down for safety. The most common reasons are a build-up of carbon on the sensing probe, a failure in the gas delivery, or a blockage in the pipe that carries waste water away from the unit.
Check if your gas prepay meter has credit and that the external gas stopcock is open.Inspect the plastic condensate pipe outside for signs of freezing or blockages.Thaw a frozen external pipe with warm (not boiling) water and reset the boiler.
Your boiler has detected that either the water pressure is too low for the system to run or the internal pump is unable to circulate water effectively.
Why it happens: This fault occurs when there isn't enough water pressure or flow to safely move heat away from the boiler's internal components. The most common reasons are a simple drop in system pressure due to a small leak or bleeding radiators, or a mechanical failure where the internal pump has seized and can no longer push water around your home.
Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.If the pressure is below 1 bar, use the filling loop underneath the boiler to top up the system.Turn the boiler off and back on again to reset the fault code.
Your boiler has detected a general internal fault and has locked itself out to protect the system.
Why it happens: This fault occurs when the boiler fails to light or detect a flame after several attempts, leading the system to shut down for safety. The most common reasons include a worn-out ignition spark, a faulty gas valve not releasing fuel, or the main control board failing to process the start-up sequence.
Turn the selector switch to the 'Reset' position (indicated by the 'R' symbol).Hold it for at least 5 seconds before releasing.Wait for the boiler to attempt to restart; if the light returns, call a Gas Safe engineer.
Your boiler has detected that the water temperature has got too hot and has shut itself down as a safety precaution.
Why it happens: This fault occurs when the water inside the heat exchanger reaches a dangerously high temperature, triggering a safety switch to cut the power. It is usually caused by a lack of water flow, often due to a failed internal pump or a blockage in the system preventing the heat from escaping. In some cases, the thermostat itself may have become faulty and is reporting an incorrect temperature reading.
Wait for the boiler to cool down completely (at least 20 minutes)Turn the selector switch to the 'Reset' position and hold for 5 secondsTurn the selector switch back to the 'Hot Water' or 'Heating' positionCheck that your radiator valves are open and the system pressure is between 1 and 1.5 bar
Your boiler is not attempting to light the flame, which means you have no heating or hot water because the system has encountered an internal startup error.
Why it happens: This fault occurs when the boiler's internal computer tries to start the ignition process but stops because it cannot detect a flame or verify that the gas is flowing correctly. The most common reason is an aging electronic component or a sensing probe that has become worn or dirty over time. Because the system cannot guarantee it is safe to stay lit, it prevents the burner from firing entirely to protect your home.
Check if your gas credit has run out or if the gas isolation valve is openTurn the selector switch to the 'Reset' position and hold for 5 secondsCheck that the system pressure is between 1 and 1.5 bar on the pressure gauge
Your boiler has switched itself off because it has detected that a part inside has become too hot to operate safely.
Why it happens: This fault occurs when the water inside the boiler reaches an unsafe temperature, triggering a safety switch to kill the power. The most common reasons are a failed pump that isn't moving water away fast enough, or a build-up of limescale and sludge that has blocked the heat exchanger.
Full guide for 25on the Potterton Performa 30 HE
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 Potterton 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