BoilerFaultCodesWorcester Bosch None Fault Code
Also written as NONE — same fault.
The Worcester Bosch None fault code means: your boiler is likely suffering from a build-up of limescale or sludge inside the heat exchanger, causing it to vibrate or 'kettle' like a noisy tea kettle.. It appears on 1 Worcester Bosch model in our database.
Technical description: Excessive burner noise, rumbling noises
What causes the Worcester Bosch None fault?
This issue occurs when debris like magnetite or limescale builds up inside the main heat exchanger, narrowing the channels where water flows. Because the water cannot circulate freely, it begins to boil rapidly and turn into steam bubbles, which creates the loud rumbling or 'kettling' noises you are hearing. Over time, this restricted flow puts extra strain on the pump and reduces the efficiency of your heating.
This problem often becomes more noticeable in autumn and winter when the boiler is under high demand and the burner stays on for longer periods.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Worcester Bosch models that show the None fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch None fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026