Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Remove EBUS wiring connections and make safe
Remove wire link between the 24 volt connections
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

With the EBUS external controls disconnected and
wire link removed is the radiator symbol still present in the display?