Set Appliance State:

Mains Power Off
Set Multimeter to AC Volts Set meter to measure AC Volts
CH Demand
Operating Switch in Heating & Water position
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Is there Mains Voltage across connector X11 connection 1 (L Black) and connector X7 connection 2 (N Blue) on Main Driver board?