Set Appliance State:

Mains Power Off
Gas Off
Turn Hot Water Tap On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset the appliance.
Test 1:
Does the boiler respond to a DHW demand i.e. fan or pump run?
Test 2:
Hot water tap off.
Apply a CH demand.
Does the boiler respond to the CH demand i.e. fan or pump run?