BoilerFaultCodesThe 6 most common faults
Your boiler is getting too hot inside, which has triggered a safety shutdown to prevent damage to the system.
Why it happens: This fault occurs when the water temperature within the boiler's heat exchanger rises too high or too quickly, triggering the safety sensor to shut down the system. The most common reasons are a faulty temp sensor giving a false reading, a pump failure that stops water from moving, or a blockage caused by sludge and limescale buildup.
Check that your radiator valves are fully openEnsure your system pressure is between 1.0 and 1.5 barTurn the boiler off and on again (Reset) to see if the fault clears
Your boiler has detected that there is not enough water in the system to operate safely.
Why it happens: This fault occurs when the internal pressure sensor detects that the system water level has dropped below the minimum safety threshold. The most common reason is a small leak in the pipework or radiators, though it can also happen if the expansion vessel has lost its air charge or the pressure sensor itself has failed.
Locate the filling loop (usually a silver flexible hose) underneath the boiler.Slowly open the one or two taps/valves on the filling loop until you hear water entering.Watch the pressure gauge and close the valves once the needle reaches between 1 and 1.5 bar.
Your boiler has too much water in the system, which causes it to shut down for safety.
Why it happens: This fault occurs when the water pressure inside your boiler exceeds a safe limit, usually because the heating system has been overfilled via the manual filling loop. It can also be caused by a faulty tap on that filling loop leaking water into the system or an internal failure of the expansion vessel which normally helps manage pressure changes.
Check that the external filling loop is turned off completelyBleed water from a radiator using a bleed key to reduce pressureMonitor the pressure gauge until it returns to between 1.0 and 1.5 barReset the boiler once the pressure is within the green zone
Your boiler's computer system has encountered a processing glitch and has stopped working to protect itself.
Why it happens: This fault occurs when the boiler's internal computer brain fails to process data correctly or loses communication with its sensors. The most common reason is an electrical glitch or a component failure on the main circuit board, which causes the system to shut down for safety. In some cases, loose or damaged wiring between the components can also trigger this software conflict.
Turn the boiler power switch to the 'Off' position.Wait for approximately 60 seconds.Turn the power back 'On' and press the Reset button if the code persists.
Your boiler has detected that the water returning from your radiators is too hot, which has caused it to shut down for safety.
Why it happens: This fault occurs when the water traveling back into the boiler from your radiators becomes excessively hot, causing the system to shut down to prevent internal damage. The most common reason is a lack of water circulation, often caused by a failing pump or a buildup of sludge and debris that blocks the main heat exchanger.
Ensure all radiator valves (TRVs) are fully open and not stuck.Check that the internal boiler pressure is between 1 and 1.5 bar.Reset the boiler using the control knob or button to see if the fault clears.
Your boiler has detected that the water inside the main heating unit has frozen, which is preventing the system from operating to avoid damage.
Why it happens: This fault occurs when the temperature sensor inside the boiler detects that the water within the heat exchanger has reached freezing point. The most common cause is the boiler being located in an unheated area like a garage or loft during a cold snap without adequate frost protection. It can also be triggered if the external condensate drainage pipe reflects a blockage caused by ice, preventing the system from circulating safely.
Check if the condensate pipe (the plastic pipe leading outside) is frozen and thaw it with warm water or a heat pack.Increase the room thermostat temperature and wait for the ambient heat inside the house to naturally thaw the unit.Reset the boiler once the system has thawed completely.
on the Ravenheat HE 80/90 / 25-30s
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