Set Appliance State:

Mains Power Off
CH Demand
Selector switch set to DHW/CH
CH temperature control set to MAX
Preheat switched OFF
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Allow the appliance to run for central heating and reach approximately 70°C.
Is the central heating operating quietly?
Note.
To reduce time taken for this test, reduce the heating circuit by turning off some radiators.