Set Appliance State:

Mains Power Off
Turn hot tap on and set flow rate to 3.0 l/min
Ensure boiler is cool
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance if required (press reset button for 2 seconds and release).
When the boiler has recognised a DHW demand (tap symbol flashing), does the fan run?
Note:
It may take approximately 40 seconds for the boiler to recognise a
demand (tap symbol flashing), this will depend upon the boiler status.
(Status code guidance CLICK HERE)