I've sort of "inherited" the use of this boiler. My father-in-law installed it years ago. I'm not really sure how he wired it but it works all winter long perfectly.
I initially wired in a timer which controlled 2 outlets which powered the combustion fan and auger. But I neglected to include the shaker control. That created a loud buzzing sound after 3 days on the timer.
It looks like I may have to rewire the entire system to make it work like it should. However as in times past, I will keep his method as a backup if it doesn't work properly. I had to do that on other projects.
It has always been a pleasure to find out that he used the neutral as the wire on the switch.