Shopping for new mod/con, set me straight!

Hi All,

I'm in upstate NY, 1960's vintage house, fin tube baseboards, original Crouse 150k btu boiler.

A tornado came thru and trees fell on my house this summer. Initially thought chimney was OK, but unfortunately learned the top of my flue was damaged. Had a mason come look and tell me it was clear, and OK to use temporarily until he could fix it next year (he just looked from the top) but I decided just before firing up the furnace to pull the exhaust in the basement. Turns out the flue tiles are collapsed, even at the basement level.

Instead of fixing the chimney, Ive decided to pursue a new mod/con boiler since mine is so old. Done tons of research, both here and elsewhere, and have learned a TON. Zeroing in on a heat only mod/con and pairing it with an indirect hot water tank.

I've done my own rough manual J and landed somewhere in the 80-85k BTU load for the house on the design day as is. Im currently tightening up insulation, windows, etc so that should drop a bit in time. I have a mix of high output and "regular" slantfin, a kickspace heater, radiation load w/ approx pipe losses:

Total of all zones @ 180 = 72340 w/ pipe losses.

The manual J tracks as being slightly higher than radiation, we had a period of a week or so of sustained -5°F -ish temps a couple years ago and the house couldn't get above 63 degrees for a few days.

Unfortunately, I'm scrambling here to get a system designed and in. I've called about 9 companies to come and i've received callbacks/quotes from only 3. Only one of them cared to measure anything, he asked for my radiator lengths. Interestingly, he is the one with the smallest boiler proposal but it's still too big, from my research.

2 of the quotes want to install 150k systems, an NHI and a Navien, "thats the size we install in every house"

The guy that measured my baseboards sized a 120k Rinnai w/a 32 gallon Buderus tankless. All 3 are well established local companies.

Unfortunately, all three only turndown to 15k btus. Of the 3, I'd chose the Rinnai based on cost alone, its cheaper than the navien by HALF and the NHI by about 40%.

I called a couple more companies to come in the next week or so. I know one of them installs viesmanns, and the 85k btu viesmann will turn down to 8.5k, which looks good compared to my zones above, but with a 70k AHRI rating, is that teetering on too small with an indirect attached? Should I push for that? He'll probably also say "We only install 150's"

Am I making a grave mistake picking the Rinnai with its 15k min? I'm sort of in a tough situation here, being the beginning of heating season and needing a solution like yesterday.

I so appreciate any advice