Welcome! Here are the website rules, as well as some tips for using this forum.
Replacement Oil Fired Hot Water Boiler - Is Size of Supply and Return Part of the Decision Process?
It's time to replace an early 1980's Weil McLain boiler - nameplate rating 167,000 DOE. Chimney vented.
Baseboard throughout first level. Recent slim-line cast iron radiators on second floor. A few old baseboards in the basement. Five zones including separate hot water tank. The zone valves have not worked well of late.
A heat loss analysis will need to be done, but I suspect the current boiler is oversized.
Water to and from the boiler is 2" copper. Same size black iron piping manifold above the boiler and a 2" iron main the full length of the basement plus 1" copper lines. Iron and copper water lines span out to baseboard and radiators.
There seems to be a large volume of water to move. Is it advisable to select a new boiler with substantial water capacity and the same 2" supply and return to match the original piping design? Peerless EC-3 would fit those criteria. Some other models by Peerless and Buderus have 1-1/2" connections and hold less water.
Thanks for your guidance.