Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
Attach temperature probe to the flow directly underneath the overheat thermostat coil
CH temperature set to MAX
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Allow boiler to ignite and establish for CH. Run boiler up to temperature, does the burner shut down at approximately 82°C or does overheat occur?
Notes:
To reduce time taken for this test you may wish to turn off some radiators.