Set Appliance State:

CH Demand
Boiler CH thermostat setting to MAX
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance if required.
(press and hold the power button for 4 seconds then release)
Allow fan to run.
Listen to the appliance and observe the display.
Approximately 5 seconds after the fan begins to run the burner should ignite and establish, this is indicated by the flame symbol appearing permanently in the display.