Set Appliance State:

Mains Power Off
CH Demand
Control Thermostat in high position
High/Low Switch in Low position
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

Allow the Boiler to Purge itself and the Burner to ignite.
Does the Boiler function correctly and do the radiators become hot?