BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because the water pressure inside the heating system has dropped too low.
Locate the filling loop valves beneath the boiler or near the heating pipes.Open the valves slightly to allow mains water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close the filling valves firmly and check the pressure gauge holds steady.
Your boiler's computer memory has been scrambled by electrical interference, which can usually be fixed by simply resetting the system.
Locate the unblock or reset button on your boiler's control panel.Press and hold the reset button for a few seconds to clear the error.If the boiler does not reset, turn the power off at the fused spur, wait one minute, and turn it back on.
Your boiler has temporarily stopped working because it cannot properly read the temperature of the water returning from your heating system.
Full guide for 14Your boiler has stopped working because the water pressure inside the system has risen dangerously high above the safe limit.
Locate your boiler's filling loop valves or key.Check that both filling valves are fully closed and not letting extra water in.Carefully bleed a radiator in your home to let out excess water until the pressure gauge drops below 1.5 bar.
Your boiler is temporarily stopping because water is not flowing properly through the system, which can cause it to overheat.
Full guide for 21Your boiler is getting too hot inside because water isn't flowing through the heating system properly, so it has safely shut down to prevent damage.
Full guide for 15on the Unical Alkon C 28 HE
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 Unical 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.
Affiliate links. We may earn a commission at no extra cost to you.