Set Appliance State:

Gas On; Pilot On
CH Demand
Isolate Mains Power to appliance as per TOPs P4
Selector Switch Winter position
Gas Control Knob in Main Burner position
Connect U-gauge to pressure test point
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

With the Main Burner alight, check the Burner pressure rises to the set pressure. (Maximum pressure is 7.6 mbar.)
Note:
When U-gauge is removed pressure test point should be tightened & checked for gas soundness.