Burner's working process is oil pump→heating(4 minutes)→fan→ignite→fire.
Fire keeps heating the exchanger inside, the fan's temp rises up. When reaching the set temp, the fan starts to suck in cold air, blow out warm air.
Test result, From plug until the fan starts to function, takes a total of 4 minutes 15 seconds.
Video link, https://youtu.be/qfkXlAI8gLk