Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4

Measurement:

If the temperature of the return sensor drops below 5°C or the temperature of the primary sensor drops below 5°C the boiler will fire until the primary sensor is at 30°C and the return sensor is 7°C.
The temperature of the appliance can be confirmed by measuring the temperature of the flow pipe as indicated by the red arrow.