Set Appliance State:

Mains Power Off
Mains Reset Switch OFF
CH Demand
Set CH temperature selector to MAX
Ensure all heating controls are calling
Set DHW temperature selector to OFF
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Mains reset switch On.
Allow boiler to fire under CH demand.
Does the system heat satisfactorily and operate quietly? (does not kettle)