Set Appliance State:

Mains Power Off
CH Demand
CH temperature control set to MAX
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.
Allow the boiler to ignite and run on central heating operation.
Is the heating operating correctly?