BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because water is not moving through the system properly, which is causing it to overheat and shut down for safety.
Why it happens: This fault occurs when the water inside the boiler gets too hot because it isn't being moved away quickly enough to the radiators. The most common reason is a failing internal pump that has stopped spinning, or a blockage of debris and sludge that is restricting the flow of water. It can also be caused by air trapped inside the unit which prevents the pump from working effectively.
Check that your system pressure is between 1.0 and 1.5 bar on the pressure gaugeEnsure all radiator valves and isolation valves under the boiler are fully openBleed your radiators to remove any trapped air that might be blocking circulationPress the reset button to see if the boiler restarts
Your boiler has detected that the water temperature in your heating system is getting too high, causing it to shut down for safety.
Why it happens: This fault occurs when the water inside the boiler is unable to move away from the heat exchanger quickly enough, leading to a rapid rise in temperature. The most common reason is either a failing circulation pump that isn't pushing the water through the system or a faulty temperature sensor that is sending incorrect readings to the boiler's computer.
Check that all radiator valves are fully openEnsure the boiler pressure is between 1.0 and 1.5 barCheck if any bypass valves are closedReset the boiler to see if the fault clears
Your boiler has detected that there is not enough water in the system to operate safely and has shut down to prevent damage.
Why it happens: This fault occurs when the internal pressure sensor detects that the system water level has dropped below the minimum required for safe operation. The most common reason is a slow leak somewhere in your radiators or pipework, or a failure in the components that regulate pressure, such as the expansion vessel. Without enough water, the boiler cannot circulate heat effectively and shuts down to prevent the main heat exchanger from overheating.
Locate the filling loop (usually a silver flexible hose) underneath your boiler.Slowly open the small valves at either end of the hose until you hear water entering the system.Monitor the pressure gauge and close the valves once the needle reaches between 1.0 and 1.5 bar.Reset the boiler to clear the fault code.
Your boiler has shut down because it has detected its internal temperature is getting too hot, usually caused by a blockage or a pump failure.
Why it happens: This fault occurs when the water inside the boiler exceeds a safe temperature limit, causing the safety sensors to shut the system down to prevent damage. The most common reasons are a failed pump that isn't moving water away from the heat exchanger quickly enough, or a buildup of debris and sludge that has physically blocked the internal pipework.
Check that your radiator valves are fully open to allow water to flow.Check that your system pressure is between 1 and 1.5 bar on the gauge.Try resetting the boiler to see if the fault clears after the system has cooled down.
Your boiler's internal computer has encountered a glitch or a configuration error and cannot communicate properly with the system.
Why it happens: This fault occurs when the boiler's internal computer experiences a software conflict or a complete data failure. It is usually caused by a physical defect in the printed circuit board's memory or a sudden electrical surge that has corrupted the system's programming.
Locate the reset button or dial on the boiler control panelPress and hold the reset button for 5 seconds, then releaseWait 2 minutes for the boiler to restart; if the code persists, a professional must inspect the electronics
Your boiler has detected that the water returning from your radiators is too hot, causing the system to shut down to prevent damage.
Why it happens: This fault occurs when the internal sensors detect that the water flowing back from your radiators is at a dangerously high temperature, suggesting the heat isn't being dissipated correctly. The most common reasons are a blockage in the system, a failing pump that isn't circulating water fast enough, or a faulty sensor sending incorrect readings to the boiler.
Check that all radiator valves are fully openEnsure the central heating system pressure is between 1.0 and 1.5 barSwitch the boiler off and on again to see if the fault clears after the system cools down
on the Ravenheat CSI 85
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 Ravenheat 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