A couple of years ago a new boiler and radiation company called Slant Fin had a series boiler package
where if you had a 200,000 btu load you installed two 100,000 btu boilers. The idea was that one of the boilers would do the early season heating and the second would kick in as the outside temperature got colder.

I have no idea how successful this concept was but have always liked the idea.

I would like to implement the same idea but have been out of the heating buisness for a long time so have forgoten how the controls would have been set up.

Any help would be appreciated.

I'd gladly go into details on my new project if you would like, I think it is a novel idea.

But I need to know what control components would be needed and how to set them.

I would be doing a mixed three zone install.