Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
CH Demand
Gain access to PCB (use Insulation Mat as required)
Heating temperature selector to OFF
Hot water temperature selector to OFF
Programmer or selector switch set to hot water and heating
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure voltage across connection 2 on connector X13 and connection 3 (neutral, blue wire) on connector X11 on the main PCB.