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
Main On/Off Control in the On position
Heating Control to Heating & Hot Water
CH Temperature Control to Maximum
Remove fixing screws from mains voltage unit and lift clear of the unit and make safe
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

If a fault code is displayed press boiler 'Reset' button.
Measure Mains Voltage across connection 4 (L) and connection 5 (N) on boiler connector block.