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How many btus should my boiler be?

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Natcunliffe
Natcunliffe Member Posts: 1
in THE MAIN WALL
I live in a 1500 square foot house in bethlehem pa and I have hydronic baseboards. The total length of baseboard heaters are 60 feet. It's a three bedroom house with double paned windows dating from 1890. It has one bathroom and we are not a big water consuming house. We have short showers and a relatively small shower head like 2 gpm. Our design temperature is about 11 degrees. We want to switch to gas heat and have gas pipe to our house already. Currently we have oil heat and electric water storage for hot water. Do we go for a combi boiler or do we keep the electric water storage tank and just go for a regular direct vent boiler. We plan to stay in the house for about 5 years so cost recovery is definitely important. the oil burner needs to go as it has packed up!! I would be interested to know thoughts on size of boiler? Combi boiler benefits versus cost of unit? Value in getting a modulating heat only boiler? Or do I just go for a standing non modulating boiler that runs less efficient but costs less?

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  • SWEI
    SWEI Member Posts: 7,356
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    A heat loss calculation

    should really be done, which will determine the water temperature required on a design day. With that size house your big concern will be the minimum firing rate of a modulating boiler.  I'd suggest looking at one of the newer combi units with a decent tank size (like the Viessmann 222-F or Rinnai QP85.)  Either would occupy a ~2' square space.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,578
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    Heat loss survey

    SlantFin boiler co has an excellent app for iPhone , iPad , and Android which will enable you to calculate your heat loss.--NBC
  • Zman
    Zman Member Posts: 7,569
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    Max

    The advise to perform a heat loss calc is right on. It is the most important step in your design.

    As a double check, your 60 feet of baseboard will never be able to put out more than about 33,000 BTU's.

    You could install a 1,000,000 BTU boiler and it would make no difference in the output of your heaters.A boiler this large would be very inefficient. for your application.

    This in going to put you into the smallest boilers available. Anyone suggesting a boiler with an output higher than 33,000 BTU's or the nearest available size, is incorrectly sizing your system.

    Swei suggested some nice models.

    Homeowner 1 will soon be promoting the Navien that he has in his house. The Navien is a much different product at a much lower price point.

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
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