100K Boiler through 1" pipe?

I'll be plumbing an econoburn 100 to my existing supply/return headers off my oil boiler. However, these headers are 1" sch. 40 with 3/4" zone lines. The headers themselves are about 16" in length and I'll be adding a piece to loop the headers together to make the primary loop for the econoburn. I see many diagrams using 1-1/4" for the primary loop. In addition, after doing some research, 1" is good for about 70k+/- BTU/Hr. Should I replumb the supply/return for a complete 1-1/4" loop?

I personally would prefer 1-1/4" on the primary loop. I don't think you'll regret it especially if there is a chance you'll add any new loads in the future.

Also, measure the I.D. I've seen inch and 1/4 pex actually be closer to 1 inch ID.

Right, if it's type M copper, 1" is fine. If it's pex, then 1-1/4" is what is needed. This is a small run, and 1" copper is good for 10gpm, in a 20F delt world this is 100Mbtu.

TS

Sorry... I should have been more clear! Both headers are steel.

The headers should be fine. But I would use 1.25 for the near boiler piping until you get to where you can add in tees for future storage.