Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
CH temperature control to maximum
DHW temperature control to minimum
Attach a temperature clamp/probe to the flow pipe (just above the overheat stat)
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

Allow the burner to ignite and heat up the system
until MAX temperature is reached (approx 85°C)
Monitor the appliance temperature.
Note:
To reduce the time for this test the heating load can be reduced
by turning off some radiators temporarily.