D.h.w. operation Medium

Biasi D.h.w. operation Fault Code

Also written as DHWOPERATION — same fault.

The Biasi D.h.w. operation fault code means: your boiler is currently providing hot water but ignoring heating demands, or it may have a sensor glitch causing it to stay in hot water mode.. It appears on 3 Biasi models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Lamp 2 ON (or Lamp 4)
Typical repair cost £90-180 (including labour)

DIY fix possible

Check all hot water taps are fully turned offEnsure there are no dripping taps or leaking shower headsTry resetting the boiler by turning the selector knob to 'R' for five seconds

Find a Gas Safe engineer

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Biasi models that show the D.h.w. operation fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Biasi D.h.w. operation fault code information on this page is sourced and cross-checked against the official Biasi service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026