Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
ON/OFF Switch in ON position
CH Temp Selector in Minimum position
DHW Temp Selector in Maximum position
Mode Selector Switch in Heat and Hot water position
Attach U-gauge to Burner Pressure test point
Gas ON
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow Fan to run, and Burner to ignite and establish.
Does the Burner Pressure increase to maximum pressure of approximately 10.0 mb?
Note:
When pressure gauge is removed the pressure test point should be tightened and checked for gas tightness.