Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
CH Demand
Use Insulation Mat as required
Gain access to the PCB
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage between the Blue wire (Pin 2) of the X12 connector on the PCB and a suitable earth.
Expect mains voltage.