Set Appliance State:

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

Measurement:

Measure voltage at connection 13, marked SL1 (brown lead) and connection 12, marked N (blue lead) on the lower of the two connector blocks on the right hand side of the PCB.