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.