BoilerFaultCodesThe 6 most common faults
Your boiler has lost its electrical power supply and cannot turn on or heat your home.
Why it happens: This fault occurs when the boiler's internal computer system is no longer receiving the electricity it needs to operate. The most common reason is a blown fuse on the main circuit board or a failure of the external power switch supplying the unit. In some cases, an internal electrical short or a faulty control board is preventing the power from flowng through the system.
Check if other appliances in your home have power.Verify that the boiler's fused spur switch is turned on.Check your home's main consumer unit (fuse box) to see if a circuit breaker has tripped.
Your boiler is failing to light or keep a flame going, which means your heating and hot water have stopped working.
Why it happens: This fault occurs when the boiler's control system attempts to start the burner but fails to detect a stable flame. The most common reasons are worn-out ignition components that can't create a spark or a faulty sensor that cannot 'see' the flame even if it is actually lit.
Check if other gas appliances in your home, like a hob, are working to ensure gas supply is active.Check that your prepaid gas meter has credit, if applicable.Press the reset button on the control panel to see if the boiler restarts.
Your boiler has detected that there is not enough water pressure in the system to operate safely, causing it to shut down.
Why it happens: This fault occurs when the internal sensors detect that the system's water pressure has dropped below the minimum level required for safe operation. The most common reason is a slow leak somewhere in your radiators or pipework, though it can also happen if you have recently bled your radiators without topping the pressure back up.
Check the pressure gauge on the boiler or pipeworkLocate the external filling loop (braided silver hose)Slowly open the valves to top up the water until the pressure is between 1.0 and 1.5 barEnsure valves are closed tightly and reset the boiler
Your boiler has lost water pressure or cannot detect enough water to operate safely, causing it to shut down to prevent damage.
Why it happens: This fault occurs when the system's internal sensors detect that the water pressure has dropped too low for the boiler to operate safely. The most common reasons are a leak somewhere in the pipework or radiators, or an expansion vessel that has lost its air charge and can no longer stabilize the pressure. In some cases, the water pressure sensor itself may have failed or become blocked with system debris.
Check the pressure gauge on the boiler or pipeworkUse the external filling loop to top up the system pressure to 1.5 barEnsure all radiator valves and system isolation valves are fully openRestart the boiler once the correct pressure is reached
Your boiler has shut down because it has detected internal temperatures that are too high, triggered by a safety sensor to prevent overheating.
Why it happens: This fault occurs when the boiler's internal water temperature exceeds safe operating limits, causing a safety sensor to trip and shut the system down. The most common reasons are a pump failure that stops water from moving or a buildup of limescale and sludge that restricts flow through the heat exchanger. Essentially, heat is being generated faster than the water can carry it away to your radiators.
Full guide for 20-21Your boiler has detected a general issue that needs checking to prevent a full breakdown.
Why it happens: This fault occurs when the boiler's internal computer detects an inconsistency in the electrical signals required to keep the system running safely. The most common reason is that the components responsible for lighting the flame or monitoring its presence are beginning to wear out or are sending weak feedback to the main control board.
Check that your home's gas supply is activeEnsure the system water pressure is between 1.0 and 2.0 barRestart the boiler by holding the reset button for two seconds
on the Remeha Gas 350
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 Remeha 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