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Residential Oil Fired Boiler Ratings

CTYankee Member Posts: 9
Good Morning: I have a circa 1964 American Standard Series A3 Model A35 1BJ1 boiler and I am planning on replacing over the next year. I am not clear on how the nameplate rating of this unit translates to a modern unit. Its nameplate states the following:

173 MBtu Gross Output
129 MBtu Water Installed Radiation
1.7 Gal/hour Firing Rate

Question: Assuming I was looking to replace this with a modern unit that can output what this unit does, what would the specs be on the new unit? Thanks!

I should add that since that boiler was installed (when the house was built) I have added nearly 600 sq ft of living space and an additional 400 sq ft of workshop space that are also heated by this boiler. Seems to handle the added load (for the last 10 years or so) with no problem, although I do keep those spaces at a lower temp most of the time (50 to 60 degrees).


    HVACNUT Member Posts: 5,478
    Your not going to take ANY info off the existing boiler to size the new one.
    A heat loss calculation must be done to properly size the system.
    Download the Slant/Fin heat loss calculator app. I think you'll be surprised how little a boiler you'll need.
  • CTYankee
    CTYankee Member Posts: 9
    I hear you and am planning on that, BUT, if I wanted to do a replacement of what I have with roughly the same output, what would I be looking for (in terms of contemporary nomenclature)?
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,378
    Basically, if your heat loss says 60000 btu's a boiler that nets 60000 btus. Never bigger.
    Gross btu's X efficiency of boiler (probably 87% for a triple pass)=YourHeatLoss.
    YourHeatLoss / .Efficiency of boiler = YourBoilerSize
    60000 / .87 =68966 btus
    Or most likely, for oil, the smallest btu's you can find. Just make sure it's a triple pass or an EK (even higher efficiencies).
    HVACNUT Member Posts: 5,478
    Yeah, a 3 section triple pass with an indirect water heater and outdoor reset or the EK-1 Frontier with their water heater.