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Sizing Indirect Tanks

Jacob G.
Jacob G. Member Posts: 9
If I go by first hour ratings, a relatively small indirect WH with a Muchkin boiler or equivalent would give me plenty of hot water.

Who wants to give me sizing guidelines for say, a 2000 sq. ft. home with 3 baths, a dishwasher, washing machine and a 55,000 btu/hr radiant system.

According to first hour ratings, an UltraStor 35 gl, for example, would be sufficient. I'm skeptical.

What do you say boys?


  • hr
    hr Member Posts: 6,106
    Got kids?

    are you into long showers? Do a lot of back to back HW useage. Clothes washing, showers, dishwasing all in a short span of time? Large jetted or soaking tub?

    How cold does your incoming water get?

    "These are a few of my favorite things," to consider when sizing DHW. Personally I'd go up a size or two.

    Never had a customer complain of too much hot water. But I have missed the boat on a number of homes. For the cost difference go with a larger tank, imo!

    hot rod

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  • Maine Ken
    Maine Ken Member Posts: 531

    Absolutely, bigger is better. Esp w/ such a small boiler. W/ 55k and small tank you will never fill a party tub!!!! Laws are laws, it takes a lot of horsepower to heat water FAST. 55k is not a lot of horsepower.
  • Nron_9
    Nron_9 Member Posts: 237

    if you go with a larger tank with good insolation and a port to clean them you can get away from larger boiler and do domestic priority and size very close to your heat load ,not to close thogh ,we still want lots of hot water on the coldest day of the year
  • Me_8
    Me_8 Member Posts: 21
    read the fine print

    in the spec. sheets most of those first hour ratings are based on 180* water and a rather large boiler.
  • Nron_9
    Nron_9 Member Posts: 237

    most give rateing at 100mbh or higher and at high flow rates to some as high as 22-25 gal per min through the coil but it is pooible to work the math if you are useing a zone valve or smaller boiler to check recovery rates remember it takes 1 btu to raise 1 gal of water 1 degree F
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