Set Appliance State:

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

Measurement:

Approximately 5-10 seconds after power is restored to the appliance mains voltage should be present between pin 3 (blue) and pin 4(brown) of connector X3 at the main PCB.