Set Appliance State:

Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Mains Isolator Switch in ON position
Selector Switch in DHW Summer position
Hot Water Temperature Control set to Maximum
Attach u-gauge to burner pressure test point
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Does main burner ignite with a burner pressure of approximately 12.0 mbar?
Note:
When pressure gauge is removed the pressure test point should be tightened and checked for gas tightness.