BoilerFaultCodesThe 6 most common faults
Your boiler has tried to light several times but has failed to create a flame, causing the system to shut down for safety.
Why it happens: This fault occurs when the boiler's control system attempts to start the combustion process but cannot detect a stable flame. The most common reasons include a worn-out ignition spark, a blockage in the gas supply, or an internal component failing to open the gas valve correctly.
Check if other gas appliances, like a hob, are working to confirm gas supply.If you have a prepaid gas meter, ensure it has credit.Press and hold the 'Reset' button for five seconds to attempt a restart.
Your boiler has stopped working because the water pressure in the system is too low.
Why it happens: This fault occurs when there is not enough water inside your heating system to safely allow the boiler to fire up. The most common reason is a slow leak from a radiator valve or a pipe joint, but it can also happen if you have recently bled your radiators and didn't top the pressure back up.
Locate the filling loop (usually two braided hoses or internal levers under the boiler)Slowly open both taps/valves to allow water into the systemClose the valves tightly once the pressure gauge on the display reaches between 1.0 and 1.5 bar
Your boiler has shut down completely for safety reasons and will not provide heating or hot water until it is manually reset or repaired.
Why it happens: This fault occurs when the boiler's control system detects a failure in the ignition process or a safety breach, leading to an immediate shutdown. The most common reasons include the burner failing to light, a loss of flame signal during operation, or an internal component like the fan or gas valve not responding correctly. It is a protective measure designed to prevent the boiler from running in an unsafe condition.
Locate the reset button on the front control panel.Press and hold the reset button for at least two seconds.Wait to see if the green light replaces the red light and the boiler fires up.
Your boiler has switched itself off because it has become too hot internally, likely due to a lack of water or a blockage preventing water from moving around the system.
Why it happens: This fault occurs when the water inside the heat exchanger reaches a dangerously high temperature, triggering a safety shutdown to prevent damage. The most common reasons are a pump that has failed to move water around the system or a blockage in the pipework that is trapping heat inside the boiler.
Check the pressure gauge on the front of the boiler; if it is below 1 bar, top up the system using the filling loopEnsure all radiator valves are open to allow water to circulateBleed all radiators to remove trapped air and then top up the pressure againCarry out a manual reset of the boiler using the control knob
Your boiler's electronic brain has detected an internal safety error and has shut down for protection.
Why it happens: This fault occurs when the boiler's internal safety checks detect a failure in the electronic components that manage gas flow and ignition. Essentially, a critical safety switch inside the control board has become stuck or damaged, preventing the boiler from firing up safely. Because the system can no longer verify that it is safe to operate, it shuts down to prevent any potential hazards.
Locate the power switch for the boiler and turn it OFFWait for 30 seconds, then turn the power back ONPress the 'RESET' button on the boiler control panel
Your boiler has stopped working because the water pressure in the central heating system is too low or a sensor has failed.
Why it happens: This fault occurs when the internal sensor detects that the water pressure has dropped below the minimum level required to operate safely. The most common reason is a slow leak somewhere in your radiators or pipework, but it can also happen if the expansion vessel has lost its air charge and can no longer stabilize the pressure.
Check the pressure gauge on the front of the boilerIf the pressure is below 1.0 bar, locate the filling loop (braided silver hose) under or near the boilerSlowly open the valves to top up the water until the gauge reads between 1.0 and 1.5 bar, then close them tightly
on the Potterton Powermax 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