Set Appliance State:

Mains Power Off
CH Demand
Turn Hot Water Tap On
CH temperature selector to Max
DHW temperature selector to Max
External controls calling for heat
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Selector switch to DHW and CH position.
Observe position indicator on diverter valve.
Test 1:
Turn the DHW inlet isolator OFF.
Position indicator should move to CH position.
Test 2:
Turn the DHW inlet isolator ON.
Position indicator should move to DHW position.