Set Appliance State:

Mains Power Off
CH Demand
CH Temperature control to MAX
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance as necessary and allow the boiler to
complete its self check.
Once the boiler has lit and established, press the spanner button once and press the up arrow until i9 (flow sensor) is displayed.
Switch between this and i14 (return sensor) to observe differential between the two sensors for at least 2 minutes after boiler has reached maximum rate (this may take up to 3 minutes).
Differential should be approximately 25°C or less.