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Thread: sizing boilers

  1. #1

    sizing boilers

    I don't have much experiance with sizing boilers can anyone give me some info on how to do this or tell me where to find it... I'm talking about the boiler itself and the piping

  2. #2
    Join Date
    Nov 2011
    Location
    Long Island, NY
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    279
    Google heat loss calculation in your free time.

    http://www.slantfin.com/index.php/pr...onals/heatloss

    Don't use any fudge factor, the programs have them built in to them.

  3. #3
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
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    4,656
    Steam or water?
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  4. #4
    Join Date
    Jan 2013
    Location
    Westchester, New York
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    19
    For a ballpark figure of BTU heat loss, multiply square footage of the house by 45 if it's old, or 40 if its new. The result will be close to your BTU heat loss per hour.

    For the correct way to do it, you have to either find an app/program/calculator to help you, as someone posted above, or use some kind of table with charts/formulas. You will have to take a ton of more measurements into consideration, such as doors, windows, insulation, etc.

    I've seen both done and the "ballpark figure" way is usually pretty close.

  5. #5
    Join Date
    Feb 2008
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    pulaski ny
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    3,258
    Quote Originally Posted by Stevel6416 View Post
    I don't have much experiance with sizing boilers can anyone give me some info on how to do this or tell me where to find it... I'm talking about the boiler itself and the piping
    bring your design to a supply house, they usually can do it for you. a heatload is important. the rule of thumb is a guess and can waste money in the long run.

  6. #6
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
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    Start with doing the heat load calculations on the structure room by room or area by area, depending on how it is zoned or you plan to zone it.

    Then you take what kind of radiation you have or are going to install and determine the temperatures you need to deliver to each.

    Then you decide what efficiency range your new boiler is going to be and it's ability or lack of ability to produce the temperature(s) that your above calculations showed you needed.

    IF the boiler itself can not deliver the temperatures you need then you need to design a system beyond the boiler that can supply these required temperatures.

    Sizing of the boiler itself will then be determined by all the above and anything else you decide you want to use it for heating. This could be domestic hot water, ice melting, garage heating, tempering of ventilation air...... the list is endless almost.

    Depending on the type and size of boiler you choose the manufacturer will always be able to supply their recommended near boiler piping schematics for each. If they don't....... choose a different brand.

    Hydronics is all about the math! If you don't do the math you're just setting yourself up for problems that will cost many times what it would have cost to do it right the first time around not to mention the potential for a very uncomfortable system to live with and a service life expectancy of sometimes less than half that of a well designed system.

    Search for books on the subject that talk about and explain the math required to design systems and then go into how to properly utilize the math to design the system. The circulator manufacturers are a very good source for software for doing a lot of the piping math, but you need to know what to plug into them. There are also some very good heat load software programs available for doing radiant and hydronic sizing.

    Have fun!

    OH! You can never put enough valves in a hydronic system.
    Last edited by firecontrol; 02-02-2013 at 01:47 PM. Reason: My mentor would turn over in his grave if I didn't add that last little comment.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  7. #7
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
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    4,656
    What those guys said, unless it's steam.

    If it's steam, forget everything they said, and size it on the radiators.
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

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