Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
ON/OFF switch in ON position
CH temp selector to MAX
Attach temperature clamps to primary flow and return pipes as indicated
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Allow fan to run and boiler to ignite.
Monitor the differential between the flow and return pipes for at least 4 minutes as the boiler operates for heating.
The differential between the flow and return pipes should remain below 20°C.
Note:
You may wish to turn off some radiators to reduce the time taken for this test.
Differential may be higher on initial start-up.