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Oversized boiler freakout

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capouch
capouch Posts: 26
edited 7:37AM in THE MAIN WALL

After years of working with 80% cast-iron boilers, I'm doing my first high efficiency install, using an NTI Trinity TI-150. I've had a LOT of learning to do!

I am restoring and refactoring an 1860s home which was previously refactored as a carriage house in 1915. We are finishing two 16' x 12' rooms now, and next summer will add an upstairs apartment of about 500 square feet.

I'm installing three vintage cast-iron radiators, 49K BTU, 23K BTU, and 16KBTU (the last one as a backup if the 23K unit can't keep up in the dead of winter).

My question: the turndown on this boiler is 25KBTU at its lowest firing, and as an older unit the TI-150 has a somewhat rudimentary control regime. I don't particularly trust AI agents, but one of them assured me that although this setup is marginal, I shouldn't have any problem with excessive cycling during the "edge months" of winter.

I'd rather hear that from a human expert, and I'm also curious about how can optimize my chances of success in this situation. The 23K radiator is a pantry type. I also have another, bigger bordenwarmer type radiator (currently stored in the garage) that I could use if necessary, but I have an eye on a much more appropriate location for it down the road. Images of both are attached.

I got great help with a previous question. I am very grateful for the willingness of experienced experts to help here.

pantryRadiator.jpg 20260916_183304.jpg 20260916_183314.jpg

Comments

  • KC_Jones
    KC_Jones Posts: 5,952

    So when everything is done you will have a total of 884 sq ft of conditioned space? Just want to confirm what you have. Also, what did the heat loss calculations tell you the load was?

    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
    GGross
  • Jamie Hall
    Jamie Hall Posts: 27,853

    Those are beautiful radiators, by the way!

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    tcovert83
  • hot_rod
    hot_rod Posts: 28,412

    The heat load of the room that the radiators are in plays into the equation

    A wild guess would be a total load around 25,000 for the 884 sq ft total?

    The modulation will help lessen cycles, on mild days, one zone calling, it would be good to know the heat load to predict cycling

    The boiler may be 3 times what you need, but the 25,000 turn down will help

    The manual will indicate if it has other functions to address cycling like

    Rate limit allows you to lock the boiler output, in your case 25k

    Step fire

    Anti cycling

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • capouch
    capouch Posts: 26

    I have run heat loss calculations on the two rooms that will be heated this season. Each calculator seems to give a varying answer, even with the same inputs. Roughly 8.5BTU/hr for the two rooms is an average. Radiators total is just above that.

    Just over 400 square feet in the short run, and yes, slightly larger rooms upstairs next year.

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