oversized boilers

[maccardi]

What reasons could there be for not oversizing a modulating condensing boiler (aside from cost). If a boiler has a 5:1 turn down ratio what is the difference in buying a 100k btu or a 200k btu unit? After all, the unit is going to modulate its firing rate for the heating demand isnt it? I can understand the reasons to not oversize a standard boiler but if you unit is modulating and resetting on OA where is the downside?

[millerman]

Same question holds true for wanting to oversize, why?
How about low fire rates, do they not go up with a higher peak btu unit? Kind of a silly question IMO, unless you don't mind throwing money away.

[maccardi]

Good point, but in reality 80% of 230k is 46k. I dont think you can even buy a boiler that small. Im guessing that even in the late spring and early fall most New York residents in a 4000 Sq' use more heat than that. My point is; isnt it better to have the extra capacity now for a couple of extra $ and maybey not need it or to need it and not have it.

[hydronicsman]

You will have to size the boiler components for the max BTU's. Anyone want to buy a 1.5 or 2" Spirovent?

Size it for the load. IF you have a 80K load now, and are going to add 20K possibly in the future, it would be foolish to get a 200K boiler.