Set Appliance State:

Gas On; Pilot On
CH Demand
Isolate Mains Power to appliance as per TOPs P4
Selector switch in CH CONTINUOUS position
Attach U-gauge to burner pressure test point
CH system should be cool
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Does the burner ignite and go to its maximum pressure?
Notes:
If power has been switched off or CH demand has been interrupted, there will be a delay of between 1 and 3 minutes before the boiler starts.
When U-gauge is removed test point should be tightened and checked for gas soundness.