Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Refit inner sealing panel
Attach U-gauge to burner pressure test point
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow fan to run and ignition sequence to commence.
Does the U-gauge show a pressure of approximately 14.8 mbar and
can the burner be heard to ignite?
Notes:
1. Inner sealing panel must be in position and its screws fully tightened for this test.
2. When U-gauge is removed pressure test point should be tightened & checked for gas tightness.