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
Unclip Diverter Valve head from the body and leave in a safe location
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Operate appliance at maximum output using service mode.
FOR INSTRUCTIONS ON SERVICE MODE CLICK HERE
Fan pressure should reach approximately 3.9 mbar or greater.
Notes:
1. The pressure measured will be negative.
2. When pressure gauge is removed pressure point cap should be replaced.