BoilerFaultCodesThe 6 most common faults
Your boiler has been temporarily stopped by an external device, such as a smart thermostat or a safety switch, which is telling the system not to run.
Check if your room thermostat or heating app is set higher than the current room temperature.Ensure any external switches or safety devices connected to the boiler are in the 'On' position.Restart the boiler using its power button to see if the external demand clears.
Your boiler has detected that the water pressure in the system is too low to operate safely, causing it to shut down to prevent damage.
Locate the external filling loop (usually a silver flexible hose under or near the boiler).Open the one or two taps on the filling loop slowly until you see the pressure gauge rise.Close the taps tight once the pressure reaches 1.5 bar, then reset the boiler.
Your boiler has automatically shut down because it has detected that the internal water temperature has become dangerously high.
Check that all radiator valves are fully open and not turned off.Ensure the external magnetic filter is clean and not blocked.Press the 'Reset' button on the boiler control panel once to see if the system restarts.
Your boiler is struggling to detect a flame when it tries to start, which means it cannot fire up to provide heating or hot water.
Check that your gas emergency control valve is in the 'on' positionIf you have a pre-payment meter, check that you have sufficient creditPress the 'Reset' button on the boiler control panel once
Your boiler has stopped working because the water pressure inside your heating system is too low.
Locate the external filling loop, which is a flexible silver hose connected to two valves under your 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 and check the display to see if the error has cleared.
Your central heating system currently has too much water inside it, causing the internal pressure to rise above the safe limit.
Locate a radiator in your home, preferably upstairs.Place a cloth and a container underneath the radiator bleed valve.Use a radiator key to open the valve slightly and release water until the pressure gauge on the boiler drops to between 1.0 and 1.5 bar.
on the Viessmann Vitodens 200-W B2HF System
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 Viessmann 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
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
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