Set Appliance State:

Set Multimeter to AC Volts Set meter to measure AC Volts
Isolate Mains Power to appliance as per TOPs P4
CH temperature selector to 0 position
DHW temperature selector to maximum position
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow appliance to self check and go to standby mode.
Turn Hot Water Tap On.
Measure voltage across connection fan live (brown lead) and fan neutral (blue lead) at the fan.
Expected voltage between 220 and 240 volts AC.