Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
Temperature control to MAX
Attach temperature clamps to the flow and return pipes underneath the boiler
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.
Measure the temperature differential between the flow and return
for at least 2 minutes after boiler has reached maximum rate
(this may take up to 3 minutes after ignition).
Differential should be approximately 25°C or less.