I may not do this install myself, but I am trying to understand it better. Here is my situation. I had a 70 year old oil steam unit that was 2000 lbs. when I finally removed it. It may have been 10% efficient at best. Most of the heat ran up the chimney. When I separated the sections, the bottom 2" connections were rusted with sediment almost solid.
My house is 2600 sf. I did a heat loss and came up with 46,000 btu's. EDR calculation came out to 300 sf (72,000 btu). The boiler I think I need is the Burnham Mega Steam 396. What other calculations do I need to take into account. Is this too small of a unit? Also, I have attached a diagram I created to understand the supply and return.