Set Appliance State:

Mains Power Off
Set Multimeter to AC Volts Set meter to measure AC Volts
CH Demand
Summer/Winter Switch to Winter
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Press reset to cancel purge cycle countdown.
Measure the voltage across connections 3 (red) and N (blue) at connector X3 on the PCB.
Expect mains voltage.