Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
Turn Hot Water Tap ON
DHW Temperature Control to MAX
Gain access to PCB (use Insulation Mat as required)
Move connector ST5 to expose terminals on PCB
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure for ac voltage across brown terminal and the white terminal at the connector ST5 on the PCB.
Expected voltage 130 VAC.