Set Appliance State:
Mains Power Off
Set Multimeter to AC Voltage 
CH Demand
ON/OFF switch in ON position
CH temp selector to MAX
DHW temp selector to MIN
Use insulation mat as required
CH temp selector to MAX
DHW temp selector to MIN
Use insulation mat as required
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Measure voltage between the pin with the brown wire and
the pin with the blue wire at connector X12 on the PCB.
Do NOT disconnect connector X12.
the pin with the blue wire at connector X12 on the PCB.
Do NOT disconnect connector X12.
Isolate as per TOPs P4
and refit as necessary