Set Appliance State:

Mains Power Off
Set Multimeter to AC Voltage Set meter to measure AC Volts
CH Demand
On/Off Switch On.
Gas On
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow approximately 20 seconds after the Boiler is switched on for the PCB to sequence the combustion purge period and measure Mains Voltage across the White wire (connection 14) and the Blue wire (connection 7) on the PCB connector.