Set Appliance State:

Turn Hot Water Tap On
Boiler DHW thermostat set to MAX
Gas On
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

Observe the burner through the sight glass, does the burner ignite and establish correctly?
Note:
To see spark through sight glass look down through the sight glass at a steep angle and slightly to the left.