Do mains matter for boiler sizing?

jalubarsky

My boiler is leaking above water line so new boiler is clearly needed. We added up my 15 rads and come up with around 270 sq ft of steam needed.  My previous Burnham boiler was rated @454 which explains my short cycling problem. I've known this since I moved in 10 yrs ago.

Looks like we are going with two sizes smaller of a Burnham which is rated @271.  
Does it matter that my house has 3 fairly long mains?  They are very well insulated with really good venting.

I clearly want the correct sized boiler and just want to make sure I do not over correct.  
I appreciate any comments.

KC_Jones

No, do not factor them in.  The boiler has 33% beyond the rating to account for piping.  With insulated pipes you need almost zero extra.

The boiler you are looking at will have ~87 sq ft of EDR in that piping factor.  That would allow you to have 140’ of 2” piping un insulated.

jalubarsky

Very helpful info which gives me confident of our decision - thank you.