Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Integral timer set to DHW ON and CH OFF
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Does the boiler recognise a demand.
(Demand is recognised when a small tap symbol appears in the display)