Set Appliance State:

Gas Off
Isolate Mains Power to appliance as per TOPs P4
CH Demand
ON/OFF switch in ON position
CH temp selector to MAX
DHW Temp Selector to MIN
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow the ignition sequence to commence.
Does the fan run?