Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
DHW Demand
Thermostat turned to MAX
Connect a U-gauge to the Burner Gas Pressure Test Point
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

Run tap on maximum flow rate.
Allow the boiler to execute its ignition sequence and the burner to ignite.
Does the burner operate at 13.4 mbar of gas pressure?
Burner pressure should be adjusted if required.
Note:
When pressure gauge is removed the pressure test point should be tightened and checked for gas tightness.