Set Appliance State:

Mains Power Off
Gas Off
CH Demand
Selector Switch in CH CONTINUOUS position
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

Does the Fan increase to high speed?
Note: There will be a delay of between 1 to 3 mins before boiler starts if Power has been switched off or CH demand interrupted.