Set Appliance State:

Gas Off
Isolate Mains Power to appliance as per TOPs P4
Attach a pressure gauge to the inlet pressure test point
Ensure NO demands
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset boiler if necessary.
With a standing pressure registered on the gauge turn OFF the appliances gas inlet isolation valve.
Turn ON the DHW tap and allow the ignition sequence to commence.
Monitor the gauge as the appliance attempts to ignite, the pressure on the gauge should be seen to drop away indicating the gas valve is opening.
Note:
1. The appliance will attempt ignition 5 times, repeat test from set appliance state as required until test outcome is determined.
2. When pressure gauge is removed the pressure test point must be tightened and checked for gas tightness.