Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Attach U-gauge to burner pressure test point
Programmer or selector switch set to hot water only
Heating temperature selector to OFF
Hot water temperature selector to maximum
Ensure heatbank is not up to temperature (this can be achieved by running the DHW with the mains power to the appliance on and the gas to the appliance turned off)
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Does the U-gauge show a pressure of at least 1mb?
Note:
When pressure gauge is removed the pressure test point should be tightened and checked for gas tightness.