Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
Attach pressure gauge to +ve and -ve pressure connections at the top of the boiler
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Allow fan to run and burner to ignite.
Does the pressure gauge show the correct differential pressure as per table below ?
Note.
1. The appliance will monitor the temperature of the system and it may take up to 4 minutes to reach maximum rate, this will only happen if maximum rate is required.
2. When pressure gauge is removed pressure test point should be
tightened & checked for soundness.