Set Appliance State:

Mains Power Off
Gas Off
Set Multimeter to AC Voltage Set meter to measure AC Volts
CH Demand
Selector switch to CH CONTINUOUS position
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage across the blue (N) and brown (L) wires at the pump.
Note:
If power has been switched off or CH demand has been interrupted, there will be a delay of between 1 and 3 minutes before the boiler starts.