Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Boiler ON/OFF switch OFF
Attach U-gauge to outlet pressure test point on gas valve
DHW temperature selector set to Mid position
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Boiler ON/OFF switch ON.
Allow boiler to heat DHW to approximately 55°C, reduce flow rate at tap to assist temperature rise if necessary.
Does burner pressure reduce as demand is met?
Note:
When pressure gauge is removed the pressure test point should be tightened and checked for gas tightness.