Set Appliance State:

Mains Power Off
Set Multimeter to AC Voltage Set meter to measure AC Volts
CH Demand
On/Off Switch On.
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure Mains Voltage across the On/Off Switch switched
live (Red/White spaded wire) on the switch and the neutral
(blue wire marked PERMANENT N) on the main terminal block.