Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Selector switch in DHW position
Attach a U-gauge to the gas valve burner pressure test point
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the burner pressure whilst sparking is occurring.
Does the U-gauge show a constant positive burner pressure at or above minimum (refer to table) while sparking is occurring?
Notes:
1. Burner pressure will only be present while the ignition is sparking, if boiler fails to ignite lockout will occur. This can be reset by turning the mains power supply to the appliance OFF and ON again.
2. When U-gauge is removed pressure test point should be tightened & checked for gas soundness.