Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
DHW temperature control set to 12 o'clock position
Attach pressure gauge to the burner pressure test point
Turn hot water tap on and set flow rate to approx. 5 litres a minute
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Appliance On/Off control set to ON position.
Reset lockout as necessary.
Allow the burner to ignite and establish.
As boiler begins to reach temperature does it modulate the burner pressure?
Note:
When pressure gauge is removed pressure test point
should be tightened & checked for gas soundness.