Set Appliance State:

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

Measurement:

Fan pressure will read negative and should be approximately -1.4 mbar or greater (e.g. -2.0 mbar).
Note:
When pressure gauge is removed pressure point cap should be replaced.