Set Appliance State:

Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Selector Switch in HW position.
Connect U-gauge to burner pressure test point.
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Is the pressure between 2.1-10.6 mbar?
Note:
When U-gauge is removed pressure test point should be tightened & checked for gas soundness.