Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Attach FGA unit to fan pressure test point
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset boiler if required.
Allow ignition sequence to start.
With the fan running the pressure measured will read negative and should be approximately -1.5 mbar or greater (e.g. -2.5 mbar) see Note 1.
Note:
1. During the ignition sequence the fan speed will increase & decrease, as will the fan pressure, but fan pressure should not be seen to drop below -1.5 mbar (e.g. -0.5 mbar).
2. Boiler may go to lockout during test, reset as required until test complete.
3. When pressure gauge is removed pressure point cap should be replaced.