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Thread: HVAC calculator

  1. #1
    Join Date
    Jul 2006
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    I am getting really close to buying this sites HVAC Calculator. How accurate is it and what kind of info will I need to know in order to do this? Example, will I have to measure rooms, know what my insulation is etc....

    Looks like hubby and I will have a project to do tonight
    With it being 108 today nothing better to do anyways.

  2. #2
    Join Date
    Nov 2000
    Eastern PA
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    HVAC Calc is as accurate as can had and easier to use then other load calc programs., and ye shall find;..
    So always seek the Truth, not just what you want to believe to be true…
    Ecclesiastes 10:2 NIV

  3. #3
    Join Date
    Jun 2006
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    I just got it yesterday and it took about 1-2 hours but once I got the hang of it - it went fast. And my husband didn't help much!

  4. #4
    Join Date
    Nov 2004
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    someone ask this it is:

  5. #5
    Join Date
    Feb 2006
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    The trial version asks about wall dimensions for each room (length, width, height which helped for my vaulted ceilings). I used interior measurements. It also asks about insulation R values, duct insulation (if any). It also asks about windows. When I used the program, I didn't realize that my windows were "Low E". My HVAC contractor told me after he looked at my HVAC Calc screens that I have Low E windows. It was an easy edit to change it to Low E windows.

    I was very pleased with the results. I ended up getting a 2 ton unit. The contractor suggested 2.5 tons because it is a heat pump. Also, he was concerned that the unit might not get down to 72 indoor if it was 105 outdoor (HVAC calc default for Denver).

    HVAC calc (or any calculation) can be imperfect. However, as I posted on another thread, Sunday it was 102 outdoors, thermostat set on 71, indoor temp was 73 only for 2 hours. The all time record high for my Denver suburb was 103 per

    I normally set my AC on 77 with the indoor fan running constantly. As the HVAC Talk pro's advised me, be sure you have HVAC Calc with the correct pull down options for your city/state (minimum and max winter/summer temps will be shown).

    The pro's on HVAC Talk and my contractor were very helpful with advice on the results (and corrections) and appreciative that I had used the program.

    Here were my two threads of questions regarding my HVAC calc results. It probably won't help you personally, but you could read it if you want.

    AC only question

    Heat pump final question

    Also, the big factor that helped me decide to go with the recommended HVAC calc 2 ton as opposed to contractor suggested 2.5 ton was MY DUCTS. The HVAC calc can estimate your duct capacity. If you have your HVAC contractor compare your duct capacity to the RATED airflow that is published by the equipment manufacturer of your proposed equipment, this will also reassure you that you won't exceed your duct capacity.

    I don't think anyone would disagree, using HVAC Calc is better than relying on a "sizing by rule of thumb" that many HVAC companies do.

    Also, the HVAC Calc has a customer support number. I only talked to the guy when I renewed my trial version, but I may have even talked to the guy that wrote the program (small company?).

    After you calculate the official (actual) values and perhaps print them, then you can experiment with the software and it will show you how much heating/cooling btu you could save with any possible additional insulation/windows etc.... This was very valuable also. Most people don't think insulating crawlspace joists is important, but it is !!!

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