Set Appliance State:

Mains Power Off
Gas Off
Set Multimeter to AC Voltage Set meter to measure AC Volts
Turn Hot Water Tap On
Purge Switch in NORMAL position
HW Switch in ON position
CH Switch in OFF position
HW Potentiometer set to maximum
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the Voltage across the Red wire (marked PL) and the Black wire (marked PW) on the Main PCB Connector marked PL2.