Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
Gain access to lower PCB panel
Ensure Central Heating and DHW are turned OFF
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure voltage between LR on the right hand connector
and mains neutral marked N on the left hand connector.
Mains voltage should be absent.