BoilerFaultCodesThe 6 most common faults
Your boiler has no electrical power, meaning the controls and display are completely dead.
Why it happens: This fault occurs when the electrical supply to the boiler's internal brain has been interrupted or a critical component has failed. The most common reason is a blown fuse on the main circuit board or a failure of the internal transformer which converts power for the display. In some cases, it can be caused by an external issue like a tripped circuit breaker or a blown fuse in the wall switch.
Check if the boiler's electrical isolation switch is turned on.Inspect your home's main fuse box to see if a circuit breaker has tripped.Check the fuse in the boiler's fused spur switch, usually located on the wall nearby.
Your boiler has shut itself down for safety because it failed to light or detected an internal problem.
Why it happens: This fault occurs when the boiler has tried to ignite several times but failed to establish a stable flame. The most common reason is a lack of fuel reaching the burner, often due to a faulty gas valve or worn-out ignition sparks that can no longer light the gas safely.
Locate the reset button on the front control panel.Press and hold the reset button for several seconds.Check if your gas supply is active by testing another gas appliance like a hob.
Your boiler has stopped working and entered a safety shutdown mode, meaning it will not provide heating or hot water until it is reset or repaired.
Why it happens: This fault occurs when the boiler has tried to ignite several times but failed to detect a stable flame, leading the system to shut down for safety. The most common reasons are a lack of gas reaching the burner or a worn-out component failing to spark or sense the flame correctly. It essentially means the boiler’s internal computer has lost confidence that it can burn fuel safely.
Locate the reset button or control knob on the front panelTurn the knob to the 'Reset' position or press the reset button for 5 secondsWait for the boiler to attempt to restart; if the code returns, contact a professional
Your boiler has stopped working because the internal fan, which safely clears exhaust gases, isn't spinning at the correct speed.
Why it happens: This fault occurs when the boiler's processor detects that the fan is not rotating fast enough to safely expel waste gases from the flue. The most common reasons are a build-up of dirt within the fan housing, worn-out bearings that cause the motor to seize, or a communication failure between the fan and the main control board.
Full guide for Fan speedYour boiler has detected an electrical wiring error where the power wires appear to be connected incorrectly, which is a significant safety risk.
Why it happens: This fault occurs when the boiler detects that the electrical supply wires are reversed, meaning the 'live' and 'neutral' power lines are connected to the wrong terminals. The most common reason is recent electrical work elsewhere in the property or a failing main control board that can no longer correctly identify the incoming power signal.
Full guide for Wiring faultYour boiler has temporarily paused its operation because it has detected a minor inconsistency in its internal readings, such as water pressure or temperature.
Why it happens: This fault occurs when the boiler's internal sensors detect a reading that is slightly outside of the normal operating range, leading the system to pause for safety. This is most commonly caused by a drop in system water pressure or a temperature sensor that is beginning to provide inconsistent data to the control board.
Check the central heating pressure gauge is between 1.0 and 1.5 barTurn the power switch to the boiler off and back on again after 30 secondsCheck that all radiator valves are open and not blocked
on the Potterton Envoy 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 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