BoilerFaultCodesThe 6 most common faults
Your boiler is struggling to move water through your heating system effectively, preventing it from heating your home properly.
Check that all your radiators have their thermostatic valves fully openEnsure your heating system pressure is between 1 and 1.5 bar on the gaugeBleed your radiators to remove any trapped air that might be blocking the flow
Your boiler has lost water pressure and needs to be topped up to work correctly.
Locate the filling loop under the boiler, which usually consists of a braided hose with one or two small valves.Open the valve(s) slowly to allow water into the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.Close the valve(s) tightly to stop the flow of water.
Your boiler is struggling to move water around your heating system effectively, possibly due to trapped air or a blockage.
Check your boiler pressure gauge and top it up to 1.5 bar if it is below 1.0Ensure all radiator valves are fully openBleed your radiators to remove any trapped air that may be blocking the flow
Your boiler has detected that water is not flowing around your heating system correctly, causing it to shut down to prevent overheating.
Check your radiator valves are fully openCheck your system pressure gauge is between 1 and 1.5 barTurn the boiler off and back on again to reset the system
Your boiler has detected that the water is not flowing properly around your heating system, which is preventing it from heating up your home or water.
Check your boiler pressure gauge; if it is below 1 bar, use the filling loop to top it up to around 1.5 bar.Ensure all radiator valves are fully open.Reset the boiler using the reset button on the control panel.
Your boiler has stopped working because the water pressure inside the heating system has dropped too low to operate safely.
Locate the external filling loop, which is usually a silver flexible hose connected to two valves under the boiler.Open the valves slowly to allow mains water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close both valves tightly immediately after reaching the correct pressure.
on the Ariston Clas HE 28
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 Ariston 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