Rule of thumbs

j a_2

I am not a huge fan of rules of thumb to finalize a question...However just to confirm my understanding, can it be said in ONE pipe steam, counter or parell flow, if you have an existing 2 inch main then your replacement boiler should not be bigger than 387 sq. ft. of steam...Does that make sense?  thanks  J A

crash2009

Yea it makes sense

that you need a 2" pipe for 387 EDR, but it does not make sense that you can estimate boiler size by the size of the existing main.  What if the previous installer installed 2" just for the hell of it. 

I think it's best to use my thumb to hold the tape measure while measuring the radiation of the building.

j a_2

re

Sorry for any confusion, but the answer I want to confirm is this, if you have a 2 inch main you should not install a steamer with anything over 387 sq. ft. of steam, give or take a little.. espically a counter flow system   Thanks  J A

STEAM DOCTOR

main size

According to Lost Art a 2" main can handle 386 square feet EDR in a parallel flow system. Counter flow systems need mains one pipe size larger then parallel flow. This has nothing to do with the sizing of the steam boiler. The steam boiler is sized to the connected radiation. Are you sizing a boiler or are thinking about replacing or adding on to a main?