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Thread: Hvac-calc

  1. #14
    Join Date
    Apr 2005
    Location
    new jersey
    Posts
    752
    once your sure of the calculations inputs and results. you can go to the tools at the top of the program and select cfm calculation. you must know the amount of CFM /tons cooling size. an axample type in 1200 cfm for 3 tons and it will tell you according to the calculations where the cfms should be per rooms. add the ductwork one time to the program input .Adding the people the way i explained it was how it was explained to me by the company who sells the program.I have been faithfully useing this program on every single job for 3 years now.I will admit that I have not derated any of my jobs. and have had very satisfyed customers. This was something I overlooked until recently reading the threads on the issue. maybe in jersey it was not as crucial.maybe when wall inputs I allway leave blank the exterier sideing type insulations and only input R value in the walls.

  2. #15
    Join Date
    Jan 2007
    Location
    Minneapolis, MN
    Posts
    415
    Is there a basement? Are the floors really insulated over the basement? Duct losses are greater in unconditioned spaces and should be insulated. If the basement is in the conditioned space it needs to be added. Why do you have so much shading on your windows? Are there awnings? Windows add allot of load. Don't count trees as shading. Not seeing the plan it's hard to tell if the inputs are correct.

  3. #16
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,705
    Sorry.

    When I said 2 people per bedroom. I meant if you have 3 bedrooms. Include 6 people for the load.
    Not list 2 people in the bedrooms, plus people in every room.
    Didn't mean to mislead you.
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    How many times must one fix something before it is fixed?

  4. #17
    Join Date
    Mar 2008
    Posts
    15

    Cool

    Yes I will have to admit I am very confused on the people/

    Do add the people expected or the total of people in the house.

    As a homeowner/ built this place, and contracted out the hvac to a reputable dealer, I still have questions about if they over sized my HVAC by a great amount. I appreciate everyones comments and will go to helping me have some piece of mind.

    To answer another post, yes this is a ranch on a full basement and in order to get a building permit it had to pass RESCHECK which is a DOE (Department of Energy) home energy efficiency check. AS the builder it was a surprise to me when I went to get the permit. The only way it would pass was if the flooring was insulated, lowE double pane windows and doors and R30 attic insulation. I have seen numerous house being built at the same time that did not have insulated flooring over a full basement.

    As for the shading most of the windows are on the front and rear which does have full length a eight foot covered porch on the front and rear.

  5. #18
    Join Date
    Apr 2007
    Posts
    6,285
    The most people that will be there on a regular basis will be 2 people per bedroom so you would only want to add 2 people per bedroom and leave the other rooms blank......unless your have in laws living with you permanently

  6. #19
    Join Date
    Jan 2007
    Location
    Minneapolis, MN
    Posts
    415
    Just add 1 person per bedroom plus one (they assume two people in master bedroom) and add them to the living room. The load is considered during peak time of the day. People in the bedrooms don't add enough during sleeping hours to matter (system is over sized during the night). The load won't make much difference and you can prove it to yourself by changing the number of people in the program and watch the load change. I would double check how they entered the info into Res Check, I have Res Check but I only use REM/Rate, if you insulate the foundation to R-10 on the exterior it should be fine and not need floor insulation (there are trade offs in the program). If you plan on using the basement you will want to insulate the walls anyway. I would also insulate the basement ground floor, it will make a big difference in comfort. It sounds like you are building an unconditioned basement and it doesn't make sense to me. I would meet with the local code inspector and clarify the construction details.

  7. #20
    Join Date
    Aug 2006
    Location
    Marco Island, Fl
    Posts
    729
    I ran the data from your second load calc with the Carrier system product data.
    At system cooling design conditions the system will produce about 50,000 btu/hr. in high speed. about a 10,000 btu/hr over-size. You have a modulating two-stage system, and if the ducts are correct, I would not worry about it.


    For your heating design conditions, the system will produce about 42,000 btu/hr in high speed. This is right on for your design conditions.

    Sounds like they sized it for heating, and you have a great system.

  8. #21
    Join Date
    Mar 2008
    Posts
    15
    Thanks Davo thats good to know. It's these little things that bug me. I do wish I had found this website during construction and it would have removed some of my troubles.

    The system has performed flawlessly and I consider it to be very energy efficient.

    Mbarson. I built a basement. It is not and was not intended to be finished. The only way to insulate the foundation for a unfinished basement would be to put Styrofoam panels on the exterior or frame the interior walls. Yes this would have worked except it is an unfinished basement. Georgia law will not allow Styrofoam below grade. Why TERMITES

  9. #22
    Join Date
    Feb 2008
    Location
    Dallas & Longview, TX
    Posts
    629
    You might try to remove all the shading from the windows and see what the load is. I think the manual says to use unshaded unless there is a room with blockout curtains/shades always closed. The covered porch still allows reflected IR heat to enter. This might bring you closer to the 5 ton unit selected (when adding 20&#37 and reflect that the program is correct.

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