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Loss Calculations

Hilly Member Posts: 427
I've been playing with some of the different software available out there.

One gives a

Total Heat Loss: 53,443

Downward to Ground: 12345

Total Infiltration Loss: 13,888

Program B gives a Total Heat Loss 49,050 and then also a Total Heating Load 62,500.

Would you size the boiler based on 'which figures??


  • Jamie Hall
    Jamie Hall Member Posts: 23,276
    Those things

    depend so much on so many assumptions...  the first thing to do is to study the program, and see what sorts of things it takes into account (or not!).  And then see what the assumptions are that are related to those things -- and especially the things which it doesn't ask about.

    Then take a look and see how closely those assumptions agree with the reality that you are dealing with.

    The two results aren't actually that far apart -- 63K vs. 79K seems like a lot, but it really isn't; anything within 10% is really good, and those average out to about 71K.

    Myself I'd be inclined to bias my selection towards the high side, but then I've always been a sort of belt and braces man.  But I'd have to know a lot about the structure you are heating and its exposure to be more confident.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Spence
    Spence Member Posts: 316
    Heat Loss

    The first step is to ensure your software program is blessed by ACCA. That way, you know the software designers have not added assumptions beyond those already in ACCA's design manuals.
  • icesailor
    icesailor Member Posts: 7,265

    Assumptions? You mean "Assumptions" made by designers from ACCA (Air Conditioning Contractors od America) for a program for cooling and heating houses with air? Those kind of assumptions? Like where the building is locared and what direction it faces? Heating only programs don't take into consideration where the sun is at 2:00 AM.

    Unless a heat/ac programs can switch off the cooling parameters when you switch to a heating side, you will have problems.

    And that is where your discrepancies come from. Making assumptions for heating that only apply to cooling.

    If it is a rally comprehensive cooling program, you need to allow for heat sources inside the envelope like refrigerators. And people and lights. In heating, it is considered as a gain that may or may not be present so don't allow for something that you can't control.

    If you work with and understand how they all work, you can make better decisions as to which is better. Heat only like IBR work best for hydronic systems. Scorched Air and frozen air will work better with air designing system. They use a bigger shotgun approach.

    I've bought and tried a whole tribe of them. None was more successful and easier to use than IBR/Slant-fin for hydronic heat. I always used the IBR as a base comparison. None ever came close. Especially the radiant ones. They were always pie in the sky programs. Maybe that's why I saw so many poor performing radiant heating installations. Overly optimistic expectations as to what you could get through a wooden floor and how much it took to heat a room when it was 10 degrees outside and the wind was gusting to over 50 MPH. from the NW and NW end of the house was cold.
  • Hilly
    Hilly Member Posts: 427
    slowly learning

    Icesailor I feel like I should just pay you to come tag along for a while to really learn some real world stuff. Most of my hedonic is practical because I do twice the reading and half the work. Plumbing is my trade but hydronics is definitely what I love.
  • icesailor
    icesailor Member Posts: 7,265
    edited May 2014

    I'm a Master Plumber first. 1994. A Journeyman before, 1967. I plumbed through the hydronic heat drought of the era of electric heat. I created a lot of opportunities for myself and had some given to me.

    You're way ahead of most. They won't ever ask questions or accept help or suggestions. When you get into dilemma's, not of your doing, and there is no  one to help you out, you figure out and learn. You have to think like whatever you are doing is being asked to do. No matter what it is, it is all related. Everything is related. If you don't know something, ask somebody. If they don't know the answer, ask someone else. But the someone that thinks they don't know, may know a lot more about something than even they know. I've never met anyone in my life that I didn't learn something from. Even if the information was wrong, it gave me something to contemplate and figure out the correct answer.

    Some of my most difficult domestic hot water problems were actually solved with hydronic hot water understandings. Reading will never make you stupid. Neither will talking about it. both ways will give you unexpected answers. None of us are born knowing it. And none of us will die knowing it all. Its what we learn during the journey that counts.