BoilerFaultCodesThe 6 most common faults
Your boiler is not receiving the electrical signal from your thermostat or timer telling it to turn on.
Why it happens: This fault occurs when the boiler is powered on but isn't receiving the necessary electrical 'command' from your external controls to start heating. The most common reason is a failure in the communication line between your room thermostat, programmer, or motorized valves and the boiler itself. Essentially, the boiler is waiting for a green light to fire up that never arrives because of a fault in those external components.
Check that your room thermostat is turned up higher than the current room temperature.Ensure your programmer or heating timer is set to 'ON' or 'AUTO'.Replace the batteries in your wireless thermostat if the screen is blank or showing a low battery symbol.
Your boiler is not receiving the electrical signal from your thermostat or programmer telling it to turn on.
Why it happens: This fault occurs when the boiler is receiving main power but isn't getting the specific 230V command to actually start heating. The most common reason is a failure in an external component like a broken room thermostat, a blown fuse in the wiring center, or a motorized valve that is stuck and failing to trigger the microswitch. Essentially, the boiler is 'waiting' for a signal that never arrives because of a break in the electrical chain outside the unit itself.
Ensure your wall thermostat is turned up higher than the current room temperatureCheck that your programmer or heating timer is set to 'ON' or 'AUTO'Check your home's consumer unit (fuse box) to see if any switches have trippedReplace the batteries in your room thermostat if it has a digital display
Your boiler is unable to send power to the water pump, which means it cannot circulate heat around your home and has shut down for safety.
Why it happens: This fault occurs when the boiler's computer sends a signal to start the pump, but detects that no electricity is actually reaching it. The most common reason is a malfunctioning main control board that can no longer switch power on, though it can also be caused by loose internal wiring or a pump that has short-circuited.
Full guide for PUMP FEEDYour boiler has failed to start because it cannot successfully light or maintain a flame, so it has safely shut itself down to prevent gas buildup.
Full guide for Ignition LockoutYour boiler has stopped working because it cannot detect enough water inside to safely heat your home.
Full guide for Dry-fire LockoutYour boiler has detected a safety issue preventing it from circulating heart or hot water, and it has shut down to protect itself.
Full guide for No Pump Feedon the Potterton Promax 15 & 24
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