Set Appliance State:

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

Observation:

If required, reset boiler.
Allow ignition sequence to commence.
Exact fan pressure will differ by flue arrangement but should be at least 1.0mb
Note.
1. The boiler will enter lockout after 4 attempts of ignition, reset as required until test is complete.
2. When the test is complete the pressure test point should be tightened and checked for gas soundness
3. Fan pressure will read as negative (e.g. -2.5mb).