Set Appliance State:

Mains Power Off
Turn Hot Water Tap On
Selector switch to hot water position
CH temperature selector to minimum
DHW temperature selector to maximum
Gas On
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

Allow ignition sequence to commence.
Observe through the inspection window.
Does the pilot ignite?
Is the flame picture satisfactory on both sides of the pilot?