Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
Remove connector marked X11 from the PCB
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Reset lockout as necessary.
Boiler switch to On.
Measure voltage across the pink leads on the connector.
Expected voltage approximately 24 volts AC.