Set Appliance State:

CH Demand
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset boiler as necessary.
Does the burner ignite and establish correctly?
Note:
Spark electrode and burner can be observed through the sight glass on the front of the appliance combustion chamber.
If a fault code occurs (other than F1 - ignition lockout) click HERE