Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
CH temperature control set to MAX
Attach temperature clamps to the flow pipe under the boiler (left pipe)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow appliance to run for CH demand.
Place a temperature probes on the plastic manifold of the return
pipe(as shown in the picture) to measure the temperature.
Does the return pipe show a higher temperature
than the flow pipe under the boiler?
Note:
Use probe instead of clamp as flow pipe is not earthed which can cause incorrect readings with the Sprint V3 FGA. Click HERE for more information.