Set Appliance State:

Mains Power Off
Selector switch in heating & hot water position
Ensure there is no demand for either CH or DHW
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

When power is switched on the LED should illuminate briefly and then the
display illuminates and show 24/30/35kW Combi for 10 seconds.
(If the display does not progress from the "24/30/35kW Combi" CLICK HERE).