Set Appliance State:

Mains Power Off
Set Multimeter to AC Volts Set meter to measure AC Volts
Apply heating demand
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage across the Live (L) and Neutral (N) leads at connector marked pump on the main terminal strip.
Expect mains voltage.