Set Appliance State:

CH Demand
Isolate Mains Power to appliance as per TOPs P4
Mode Switch in LOW position
Connect a U-gauge to the Burner Outlet Gas Pressure Point
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow the boiler to complete its ignition sequence and the Burner to ignite.
Does the Burner operate at its set gas pressure between 7.5 mb and 13.4 mb?
Note:
When U-gauge is removed pressure test point should be tightened & checked for gas soundness.