Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Gas Off
Disconnect the ignition and earth leads from the spark generator
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Shortly after the fan begins to run sparking should be heard from the spark generator for approximately 5 seconds.