Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Ensure No CH demand
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow burner to ignite and establish.
Turn off DHW demand and observe flame through the sight glass.
Does the flame extinguish immediately or does the
burner remain alight after demand has ended?
Note:
If no tap is located by the boiler then use the DHW isolation valve
under the appliance to turn off demand.