BoilerFaultCodesThe 6 most common faults
Your boiler has tried to start up but cannot light the gas flame, which means your heating and hot water will not work.
Why it happens: This fault occurs when the boiler's control system attempts to light a flame but fails to detect one after several attempts. The most common reasons include a lack of gas reaching the burner, a worn-out spark electrode that cannot create a spark, or a faulty internal component failing to signal that the gas is lit.
Check that your gas pre-payment meter has creditEnsure the gas stopcock is fully open and other gas appliances like the hob are workingPress and hold the reset button for five seconds
Your boiler has detected that there is not enough water in the system to operate safely, causing it to shut down temporarily.
Why it happens: This fault occurs when the internal sensor detects that the system's water pressure has dropped too low for the boiler to operate safely. The most common reason is a slow leak in the pipework or radiators, though it can also happen if you have recently bled your radiators without topping the water back up.
Locate the filling loop (the flexible silver hose) underneath your boiler.Slowly open the valve(s) to allow water into the system while watching the pressure gauge.Close the valves tightly once the gauge reaches between 1.0 and 1.5 bar.Press the reset button on the boiler control panel.
Your boiler is trying to start up but cannot light the gas to create a flame, meaning you will have no heating or hot water.
Why it happens: This fault occurs when the boiler's control system attempts to light the burner but fails to detect a stable flame after several attempts. The most common reasons are a lack of gas reaching the unit, worn-out spark electrodes that can no longer create an ignition, or a faulty internal component failing to send the 'start' signal.
Check if other gas appliances, like a hob, are working to confirm gas supplyVerify that your prepaid gas meter (if applicable) has creditPress the reset button or turn the control knob to 'Reset' for 2 seconds
Your boiler has detected that one of its outer side casing panels is not fitted correctly or is loose, which prevents the boiler from operating safely.
Switch off the boiler and allow it to cool.Remove the front cover if necessary to access the side panels.Check that the side panels are securely clipped into place and the seals are intact.Ensure all fixing screws are tightened, then restart the boiler.
Your boiler has detected that water is not circulating properly through your heating system, so it has safely shut down to prevent damage.
Check your boiler display for the water pressure gauge reading; it should be between 1.0 and 1.5 barIf the pressure is below 1 bar, use the filling loop underneath the boiler to add water until it reaches 1.5 barTurn off the boiler at the wall, wait 30 seconds, and turn it back on to reset the system
Your boiler has detected that the exhaust gases are getting too hot, so it has turned itself off to prevent overheating.
Full guide for H21-064on the Ideal Mini C28
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 Ideal 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