Set Appliance State:

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

Observation:

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