BoilerFaultCodesThe 6 most common faults
Your boiler has failed to light, which means your heating and hot water will not work until the gas supply is restored or a internal ignition fault is fixed.
Check that your gas meter has credit (if using a prepay meter).Ensure the gas emergency control valve is in the 'on' position.Try resetting the boiler by turning the control knob to 'Reset' for 5 seconds.Check if other gas appliances, like a cooker, are working to confirm your gas supply is active.
Your boiler has too much water inside it, which has caused the system to shut down for safety.
Check that the internal or external filling loop valves are fully closed.Bleed water from a radiator using a bleed key to reduce the system pressure.Monitor the pressure gauge to ensured it returns to between 1.0 and 1.5 bar.Reset the boiler once the correct pressure is reached.
Your boiler has tried to light several times but has failed to detect a flame, causing the unit to shut down for safety.
Check that your gas emergency control valve is open and you have credit on your gas meterCheck if other gas appliances in your home, such as a hob, are working correctlyReset the boiler by turning the control knob to the 'Reset' position for five seconds
Your boiler has become too hot and has shut itself down for safety, likely because water is not moving through the system correctly.
Check that all radiator valves are fully openEnsure the boiler pressure is between 1.0 and 1.5 barTry to reset the boiler by turning the control knob to the 'Reset' position for 5 seconds
Your boiler has stopped working because the water pressure in the system has dropped too low to operate safely.
Locate the filling loop (usually a silver braided hose with small tap handles under the boiler).Slowly open both taps to let water into the system while watching the pressure gauge.Close both taps tightly once the needle reaches between 1.0 and 1.5 bar.
Your boiler has stopped working because water is not circulating correctly through the pipes, likely due to a faulty pump or an air bubble.
Check that all radiator valves and boiler isolation valves are fully openBleed your radiators to release any trapped air from the systemPress the Reset button on the front of the boiler to see if the code clears
on the Heatline Vizo 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 Heatline 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