Set Appliance State:

Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Purge Switch in NORMAL position
HW Switch in ON position
HW Potentiometer set to maximum
Remove Plastic Cap (1) on Modureg
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

Allow boiler to complete its ignition sequence.
As burner lights at full rate is the plunger on Modureg pulled in to the solenoid.