Set Appliance State:

Mains Power Off
Turn Hot Water Tap On
Flow rate set to 3 litres a min
Boiler DHW thermostat set to MAX
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Does the boiler recognise a DHW demand?
(demand is recognised when the tap symbol in the display is flashing)