Set Appliance State:

CH Demand
Isolate Mains Power to appliance as per TOPs P4
Selector switch to heating and hot water position
CH temperature selector to maximum
DHW temperature selector to minimum
Attach U-gauge to gas valve outlet pressure test point
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow boiler to fire.
Does the burner pressure increase to its set pressure after approximately 90 seconds? Does the CH system begin heating correctly?
Note:
1.If the CH burner pressure has been set at its minimum rate, then the burner pressure will not increase.
2.When the U-gauge is removed, ensure the pressure test point is checked for soundness.