Set Appliance State:

Mains Power Off
CH Demand
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Preheat switched OFF (ECO button illuminated) A.S.A.P
after power reinstated.
Watch the syphon as the boiler is running.
The syphon should fill both chambers then empty quickly and completely.