Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
DHW Demand
Gain access to PCB (use Insulation Mat as required)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Press reset to cancel purge cycle countdown.
Measure the voltage across connections 3 (blue) and 4 (black) at connector X16 on the PCB.
Connections are numbered 1-5 from left to right.
Expect mains voltage.