Set Appliance State:

Gas Off
Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Attach U-gauge to gas inlet pressure test point
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Cancel purge cycle & if required, reset boiler.
Allow ignition sequence to commence.
Inlet pressure should remain above N.G. 18 mb, L.P.G. 29 mb throughout the ignition sequence (see note).