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  1. #1
    Join Date
    Oct 2004
    Posts
    76

    HVAC calc questions

    So I decided to get a copy of the software. Very neat and thorough. Took me a while to get all the stats down for my home.

    Anyway I've got a couple of questions on how to properly enter the information into the program.

    First, when I went to the design conditions screen, I changed it to the DFW area in Texas and pressed the change button, but it doesn't keep the settings. It keeps reverting back to some city in Iowa. What's going on with that?

    Second, after compiling all of the rooms in my home, it seems that the cooling load is about right for what I have now, but the heating load is just off the scale...like 190k btu for a 2800 sq. ft. house. The furnace I have now puts out around 98k btu and does a good job for the whole house. I can only assume this is because of the design conditions not working right.

    Third, when you enter the information for the separate rooms in the house, I have entered the square footage for each wall. Now not all walls in every room are exterior walls, so for the interior ones I have a wall of certain square footage entered with no insulation and a hollow wooden door for entry. Does this adversely affect the infiltration for the room as a whole? I mean, does the software take this to mean outside infiltration? I was looking at a couple of rooms where I did this and the heat loss seemed rather high...but again this could be because of the design conditions problem.

    Fourth, when I input the square footage for the floor in each room, I always select concrete slab on grade with no edge insulation. This is about as close as I could get to my actual conditions. The foundation is a concrete slab; I have no idea if there is any edge insulation, so I just select no, but the majority of the floor has carpet. How should I go about entering this?

  2. #2
    Join Date
    Sep 2007
    Location
    Lucedale, Ms
    Posts
    27

    Confused

    The software you purchased should have came with a book. If the book is not clear enough for you then it should have a phone number for a tech. service dept. and they can fill in the blanks. This should be your best bet as they have been replying to many different questions. I don't know which software you have and I may have a different brand.

  3. #3
    Join Date
    Dec 2006
    Location
    Arkansas
    Posts
    292
    I do not use HVAC-Calc, but Manual J would not have you entering interior walls. If you have done so the software probably thinks you have uninsulated exterior walls. That, coupled with it using a city in Iowa would likely explain the high winter load and a reasonable summer load. If you switch the city to Dallas you will likely see the summer numbers skyrocket and the winter numbers come down some.

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,741
    With HVAC calc. You are not suppose to enter walls or ceilings that have no load.
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  5. #5
    Join Date
    Feb 2007
    Posts
    999
    Quote Originally Posted by txnoob View Post

    First, when I went to the design conditions screen, I changed it to the DFW area in Texas and pressed the change button, but it doesn't keep the settings. It keeps reverting back to some city in Iowa. What's going on with that?
    When you entered DFW, did you click on 'use this setting'?

    AM

  6. #6
    only enter exterior walls. when you enter interior walls with no insulation the program thinks you have an exterior wall with no insulation and as such the loads will be off the chart.

  7. #7
    Join Date
    Jan 2007
    Location
    Minneapolis, MN
    Posts
    415
    Is this a registered copy? It sounds like you are using a demo version.

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