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Thread: Hvac-calc

  1. #1
    Join Date
    Mar 2008
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    Hvac-calc

    The HVAC-CALC manual suggest adding in 20% to the calculated load.

    Do you also add 20% to the CFM?

    I have a Infinity Heat pump that was installed by the contractor we selected. At the time we were negotiating they wanted us to go with the zoning package but we declined because of cost. Is there any other place to get the Infinity zoning other than a Carrier dealer?

    The system we had installed is the Infinity 17 38YDB0060/FE4ANB006.
    Would someone like to take a look at our number s and see why I have such a big system? Works great though.
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  2. #2
    Join Date
    Jul 2001
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    Gold Coast of Connecticut
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    Cieling load, basement or floor load?

    Put the whole calc here.
    Aire Serv of SW Connecticut- Gas heat, dual fuel and central a/c systems installed and serviced

  3. #3
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    Mar 2008
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    15
    Im Sorry, not sure what you are asking? I posted the report. Do you need one with more info?

  4. #4
    Join Date
    Sep 2005
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    Texas
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    if you add 20% to the load then you need to match the load to the equipment that will handle the load. It gives you a cfm selection but you have to chose the equipment in order to know what cfms you will be using

  5. #5
    Join Date
    May 2007
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    DC Metro Area (MD)
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    Has that 5-ton Infinity ever gone into 2nd stage--for a reasonable amount of time? You should be able to check this on the Infinity control.

  6. #6
    Join Date
    Mar 2008
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    15
    Thats a good question. How would I tell? I am sure it's om the thermostat and I know how to enter the service menu.

  7. #7
    Join Date
    May 2007
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    DC Metro Area (MD)
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    Someone fluent with the Infinity control will have to direct you there. I looked online but I'm not sure if I should give this sort of information on a public forum per site rules, since it would allow other information/settings to be visible and maybe even editable.

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    I don't see a people load on that report.
    Nor did I see an infiltration load.
    These would be needed to see if you made a mistake.
    And then over the internet its stillnot something we can tell for sure.

    That program also wants you to list 2 people per bedroom, did you.
    What infiltration rate did you use.

    Also, make sure you have orientation correct, that also makes a big difference.
    HVAC CALC tells you the capacity the unit must deliver, NOT the nominal rating.
    In your report, you need a unit that can remove 28,150 BTU's sensible, at a 75*F indoor temp, many 3 ton units can't do that.

    Carrier Infinity zoning system=Carrier dealer.
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  9. #9
    Join Date
    Mar 2008
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    OK, Lets try this report. I did make some changes based on people and now it says I need a 3.5 ton. This is without any fudge factored in. Infiltration is listed on the report and I selected normal construction which this house is not. We have an excellent vapor barrier with Ty-vex that I personally sealed every joint with the tape.
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  10. #10
    Join Date
    Jan 2004
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    Lancaster PA
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    Looks good.
    Where is your ductwork located. That can add load also.
    A 3.5 ton heat pump won't meet your sensible load at your ID design temp, so they allowed for that and increased its size base on that.
    If your ductwork is in the attic, they may have allowed for the additional load it adds.

    Yaking into consideration the load on the ductwork, and the derate for the ID design temp it may have to be a 4 ton unit ot meet your requirements.
    After that, they may have gone the next size up because its a heat pump, trying to save you money on your heating bill.
    They may have used lower insulation valvues. Different load programs use different values for infiltration, and that will change the load it says your house needs.


    Of course thats speculation that they did a load calc.
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  11. #11
    Join Date
    Apr 2005
    Location
    new jersey
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    I counted 33 people added to these rooms. I would only add people to the areas where they will be during the hottest time of the day Peak load. Get rid of all those people and keep people in the main rooms of the house. Do you see your self haveing 33 people in the house between 2 and 5 pm ? I allso add 20 percent to my heat load only. other may differ but I can say what works for me.

  12. #12
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    Jan 2004
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    Lancaster PA
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    I didn't take notice to that.

    Gotta wear my glasses more often.
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  13. #13
    Join Date
    Mar 2008
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    15
    Duct work in basement. I added people based on one of the post.

    As stated do I need to increse CFM for each room by the amount of increase in unit size

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