steam boiler sizing

Jim_83

I am replacing a steam boiler heating a 2 story house with attic. The boiler will be heating the second floor and attic. The first floor is a separate apartment and has its own steam boiler.

My question concerns the boiler sizing. From reading the posts I know it is very important to size a steam boiler based on the connected load.

The connected load is 180 square feet steam. There is a boiler rated at 158 square feet steam and the next size is 271 square feet steam. I know the rule is to pick the next size higher, but in this case, is 271 sq ft too big a boiler. Would I be better off with 158 square feet steam boiler? The boiler will be gas fired.

What are the options?