Set Appliance State:

Mains Power Off
Mode selector switch to Off/Reset position
Set Multimeter to AC Volts Set meter to measure AC Volts
Turn Hot Water Tap On
Hot water temperature control set to maximum
Use insulation mat as required
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage across live connection (brown wire) on connector M14 on the main PCB and a suitable neutral.
Note:
Connection is shown disconnected for illustration purposes only, test must be carried out with connection still fitted on main PCB.