Boiler sizing help needed

cegan

I have a Crane Sunnyday 102 gas hot water boiler from 1964 that I am looking to replace. The rating plate on the side of the boiler appears to have two different ratings. The NET I-B-R RATING just has a single rating that says WATER 150,000 BTUH. The A.G.A. rating says INPUT 250000 BTUH and OUTPUT 200000 BTUH. Is this a 150000 or a 200000 BTU boiler?

EBEBRATT-Ed

You should not go by the rating plate on the old boiler as most were oversized. + most homes have had insulation added and windows replaced since 1964.

The right way is to do a heat loss. Most use the "Slant Fin App" that you can download. It is fairly easy to do and is reasonably accurate,

250,000 is the amount of gas burned (input)

200,000 is what is left after subtracting the heat going up the chimney

150,000 is what is left over to heat the baseboard after the piping losses

New boilers are rated slightly different

Tom_133

EBEBRATT-Ed is spot on here. For fun the other day I put my house info in the slant fin app and then the current outdoor temp (-12) it came back with 34K of heat loss, I jumped on my computer brought up my boiler and checked boiler BTU output at that moment and it was nearly spot on. Super impressive free App. Keep in mind its only as good as the info you put in it, try to be as accurate with windows, doors, insulation, etc.

cegan

Okay thanks Ed and Tom. I have bids on a Crown AWR-140 140000 BTU, a New Yorker CG70
198000 BTU and a Burnham X2 Nat245M 208000 BTU. Maybe the Crown would be big enough if the old boiler is oversized. Need to run the Slant Fin App yet to see what it says.

Hot_water_fan

If you have usage records, you can use this:
https://www.greenbuildingadvisor.com/article/out-with-the-old-in-with-the-new

Peter_26

I would definitely reconsider accepting any of the bids or do business with them since it looks like none of them performed a heat loss calculation. You might be having equipment installed that is 3-5 times larger than what you need. I think it shouldn't be up to the homeowner to tell them what you need, but that's just my opinion.

hot_rod

Natural gas? What type of distribution, baseboard, radiators?

KC_Jones

cegan said:

Okay thanks Ed and Tom. I have bids on a Crown AWR-140 140000 BTU, a New Yorker CG70
198000 BTU and a Burnham X2 Nat245M 208000 BTU. Maybe the Crown would be big enough if the old boiler is oversized. Need to run the Slant Fin App yet to see what it says.

Serious question, how big is your mansion?

The smallest one in that list could quite happily heat at least a 4000 sq ft home, unless it's made of glass.

Heatloss calculations need to be done.

EBEBRATT-Ed

@cegan you might post your location and check 'find a contractor" on this site. if your other contractors are not doing a heat loss you could use someone better

cegan

Thanks guys much appreciated. It's about a 2900 sq.ft. 2 story built in 1900 in northeastern Wisconsin. It has 19 windows. There are 15 cast iron radiators. It uses natural gas. KC it's interesting you would say the 140000 Crown would probably work. I have a different 3200 sq.ft. older 2 story property that has a 10yr old Bryant BW-3 boiler with 150000 input and 120000 output (all on one zone) and the people upstairs get so warm they are covering two of their radiators. I told all 3 contractors about the Bryant but it didn't seem to matter much to them as far as sizing goes.

I am trying to get the simplest and most reliable unit I can find because I am concerned they could disappear. The Bryant I talked about has a solid Dunkirk casting in it. Not sure about the quoted units.
I wish the crown didn't have the expensive to replace circuit board controller in it.

Ed and Peter--I think you are right and I am getting a couple more quotes. It's funny how the bigger contractors are not always the best.