thoughts on 1 vs 2 boilers

JIK

Wishing to install Midco with WM 580 replacing old team boiler;

Feasibility?



The old boiler was a Crown C-247 650,000/ 480,000 single pipe steam system in a 10,000 square foot historic registry mansion.



Myself and other boiler installer both came up with almost identical EDR for full radiation units and allowances totaling 1550.



(Hmmm...After reading Quad City Dave's posts on Best restoration, interesting notion to size as WM 680 to allow for additional rads upon future rooms sq. ft. expansion.)



According to the various past occupants and owners, 39 rad system always sucked.

Even so, with a boiler running at ridiculously low efficiency and on it's last legs, building warmed up surprisingly well, considering 80+ mostly bigs windows, little insulation in the walls, bad rad vents, main vents as practical joke, etc.



I have one shot at doing excellent upgrade, was looking to install WM 580.

What/ how recommendation for proper Midco product and install methodology?



The mansion itself is amazing, and once heating actually puts out nicely, have tenants lined up to lease spaces.



Ay guidance, assistance would be most appreciated in this endeavor.