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 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
Your boiler has detected that there is not enough water inside it to operate safely, so it has shut down to prevent internal damage.
Locate the external filling loop, usually a silver braided hose with one or two valves located underneath the boiler.Open the valves slowly to allow mains water into the heating system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.Close the valves tightly and restart the boiler.
Your boiler has detected a internal problem and has safely switched itself off to prevent potential damage or unsafe operation.
Full guide for FLASHINGon the Potterton Envoy Plus
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