Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Voltage Set meter to measure AC Volts
Control Thermostat in the Off position
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage across connection 2 (Black wire) on the Interconnection Board connector marked CM1 and the Live wire (Brown) marked L on the main connector block.