Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Attach FGA Temperature Clamps
on flow and return pipes as shown
DHW thermostat on MAX
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow boiler to ignite and run for at least 2 minutes.
Measure the difference in temperature between the flow and return pipes.
Is the differential approx. 22°C or lower?