Boiler displays error 16, often related to domestic hot water flow detection problems.

Safety: Turn off power and close the cold water inlet to the boiler before removing any DHW components.

• Check DHW demand recognition: Open a hot tap fully and see if the boiler recognises demand (DHW symbol or temperature change on display). If not, suspect the flow sensor.
• Clean inlet filter: On many Biasi combi boilers, there is a filter on the cold inlet. Isolate and remove it, then clean any debris.
• Inspect flow sensor/turbine: Remove the DHW flow sensor housing and check that the turbine spins freely. Descale or replace if jammed.
• Engineer electrical test: A technician should verify the sensor output to the PCB and replace the sensor if no pulses are detected when water flows.