BoilerFaultCodesThe 6 most common faults
Your boiler has detected that the water pressure inside the heating system is too high for it to operate safely.
Locate a radiator in your home with a bleed valveOpen the valve using a radiator key to release a small amount of water into a clothCheck the boiler pressure gauge until it drops into the green zone (usually between 1.0 and 1.5 bar)Close the radiator bleed valve tightly
Your boiler has temporarily stopped working because the water pressure inside the system has dropped too low.
Locate the filling loop valves underneath your boiler.Open the valves gently to allow water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close the valves tightly and check the digital display to see if the error clears.
Your boiler has detected an internal communication error and has safely shut itself down as a precaution.
Full guide for 001Your boiler has failed to light the flame properly and has stopped attempting to heat your home or water for safety reasons.
Full guide for 003Your boiler has detected a false flame signal, meaning the system thinks the burner is lit when it should be turned off.
Full guide for 004Your boiler has detected that it is not receiving enough water flow to operate safely or effectively.
Full guide for 012on the Navien NCB500
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 Navien 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
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
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