Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow the boiler to fire for Hot Water and reach a stable reasonable operating temperature.
Use two temperature probes on the plastic manifold of the flow and return pipes
(as shown in the pictures) to measure the temperature differential.
Expect a temperature differential of approx 24°C or less.
Note.
Use probe instead of clamp as flow pipe is not earthed which causes
incorrect readings with the Sprint V3 FGA. Click HERE for more information.