BoilerFaultCodesThe 6 most common faults
Your boiler has switched itself off because the water inside became too hot, likely due to a circulation issue.
Why it happens: This fault occurs when the water inside the boiler exceeds a safe operating temperature, triggering a safety shut-off to prevent damage. It is usually caused by a blockage in the system or a failing pump that is no longer moving hot water away from the heat exchanger quickly enough. In some cases, the internal sensor responsible for monitoring heat may have developed a fault and is providing an incorrect reading.
Locate the manual reset button on the control panelFirmly push the reset button in to restart the systemCheck that all radiator valves are open and the pump is running
Your boiler has stopped itself for safety because it failed to light or stay running, and it needs to be manually reset.
Why it happens: This fault happens when the boiler tries to start but fails to detect a constant, safe flame. It is usually caused by a worn-out ignition spark, a blocked pilot light, or a gas valve that is no longer opening correctly to let fuel into the burner.
Locate the lockout reset button on the control panelPress the button or wait 10 seconds and turn the control knob to 'Off' then back to 'On'Check that your gas supply is active and credit is on the meter
Your boiler has become too hot and has automatically shut itself down to prevent damage.
Why it happens: This fault occurs when the water inside the boiler exceeds a safe temperature limit, causing a safety switch to cut the power. The most common reasons are a pump failure that stops water from moving or a buildup of debris that blocks flow through the heat exchanger.
Wait for the boiler to cool down completely (at least 20 minutes)Locate the manual reset button, typically found behind the small pull-down door or on the control panelPress the button firmly to reset the safety trip and wait for the boiler to restart
Your boiler is failing to light the gas burner and has gone into a safety lockout mode to prevent unburned gas from building up.
Why it happens: This fault occurs when the boiler's control system attempts to start the heating process but cannot detect a stable flame. The most common reasons are a lack of spark from a worn ignition lead or the gas valve failing to open and deliver fuel to the burner. Because the boiler cannot confirm the gas has lit safely, it shuts down to prevent any hazards.
Full guide for Burner fails to lightYour boiler has failed to start because it cannot detect a flame, meaning you currently have no heating or hot water.
Full guide for Lockout lightYour boiler has lost all electrical power, meaning it cannot provide any heating or hot water until the power supply is restored.
Full guide for Mains light offon the Ideal Concord Super Series 4
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