Set Appliance State:

Set Multimeter to AC Volts Set meter to measure AC Volts
CH Demand
Isolate Mains Power to appliance as per TOPs P4
Boiler on/off switch ON
Gain access to appliance terminal block connections
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure voltage across connection L2 and N (neutral).
Note:
If no external controls are fitted a link must be fitted between connections L1 and L2.