Set Appliance State:

Mains Power Off
Set Multimeter to AC Voltage Set meter to measure AC Volts
Turn Hot Water Tap On
Ensure the Boiler has not reached operating temperature
Boiler Operating Switch / Programmer set to WATER only
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage across connection 2 (Orange wire) on connector X5 and the Neutral (Blue wire, connection 2 marked N) on connector X7 on the main PCB.