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  1. #1
    Join Date
    May 2008
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    23

    Question: What's the difference between Cooling & Heating Calculation Load?

    Hi i've been designing and do cooling load calculation in our country. Now, im here in the USA and there's snow and lots of freezing temperature.

    my question is, if i compute for the cooling load (example 50TR to cool down the offices) is it the same load for the heating? I mean it's also 50TR for the HEAT required during winter/snow?


    thank you in advance!

  2. #2
    Join Date
    Mar 2004
    Location
    Grottoes VA
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    5,856
    Depends on were your located, the short answer is no, there are two different loads.

    Look at it this way.

    Indoor temp of 75 degs in summer, outside temp of 100 degs, thats a 25 deg difference.

    Indoor temp of 70 degs in winter, outside temp of zero, thats a 70 deg difference.
    Karst means cave. So, I search for caves.

  3. #3
    Join Date
    May 2008
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    23
    Quote Originally Posted by karsthuntr View Post
    Depends on were your located, the short answer is no, there are two different loads.

    Look at it this way.

    Indoor temp of 75 degs in summer, outside temp of 100 degs, thats a 25 deg difference.

    Indoor temp of 70 degs in winter, outside temp of zero, thats a 70 deg difference.
    got it.

    how about the equipment (ex. chiller or package AC units)....if i compute 50TR for cooling and 70TR for Heating if i bought the chiller or AC equipment, do i need to buy 70TR capacity with capable of doing HEATING and COOLING?

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,120
    You should intern for a design/engineering firm before you do this yourself.
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  5. #5
    Join Date
    May 2008
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    Quote Originally Posted by beenthere View Post
    You should intern for a design/engineering firm before you do this yourself.
    yup i'll work as entry level hvac engineer....but i want to know also the answer to my question....i can easily understand if you give me some idea.

    thanks

  6. #6
    Join Date
    Jan 2004
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    Lancaster PA
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    ALL equipment must be sized to meet the load requirement of the season it will operate for.
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  7. #7
    Join Date
    May 2008
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    Quote Originally Posted by beenthere View Post
    ALL equipment must be sized to meet the load requirement of the season it will operate for.
    yeah thats right.

    thats why i give example....so i can't buy split type AC equipment (indoor unit + ACCU) that can do two things....HEAT during snow/winter/cold season and COOL during summer season?

    i just wonder why my car AC system can do heating and cooling.

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,120
    Cause your car A/C doesn't heat the car.
    Your cars heat comes from the engine, not the air conditioner.

    There are units that can do both.
    But since you want to design for commercial. You can't be taught how to do it online.
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  9. #9
    Join Date
    May 2008
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    23
    Quote Originally Posted by beenthere View Post
    There are units that can do both.
    thanks!

    if they can do both, what size or capacity should i select?....example 50TR for cooling required to cool down the offices and 70TR for heating to provide heat during winter season.

    do i need to specify 50TR cooling and 70TR heating capacity i need to AC manufacturer?...or i'm good with just 70TR capacity?

  10. #10
    Join Date
    May 2004
    Location
    Rapid City, SD
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    7,415
    You're an engineer, it doesn't matter... just blame the guys who put it in when it doesn't work!

    Sorry, ahem, I mean welcome aboard! lol

    This is an interesting question, and honestly I don't have any "by the book" answers.

    What I would say is this though, make sure you have enough heat to keep things comfortable, but since you're doing commercial, you'll almost always have way more need for cooling vs heating, which will lead your heating system to be plenty over sized.
    "If you call that hard work, a koala’s life would look heroic."

  11. #11
    Join Date
    Feb 2005
    Location
    Barrie, Ontario
    Posts
    4,622
    Let me complicate this for you...

    One calculation is called heat gain and the other heat loss. There is no set size or load for a home, business or outhouse because the outdoor design temperature that is used to calculate heat loss or heat gain depends entirely on location on this planet's surface. Design humidity must also be taken into consideration. Insulation, building materials, occupancy, appliances all play a part in load calculations.

    Load calculations are not a guessing game for those who need to do it right. In the case of residential, it's probably the difference between satisfying a customer or not... but in the world of commercial/industrial it can be several million dollars worth of difference. You either do it right... or don't do it.

    It should be obvious to anyone who does them, that there would be a set of design temperatures/humidities for both, gain or loss.
    Is this a Fabreze moment? C.Y.D. I'm voting white elephant. 2’.
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  12. #12
    Join Date
    May 2008
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    23
    Quote Originally Posted by gruntly View Post
    .

    Load calculations are not a guessing game for those who need to do it right. In the case of residential, it's probably the difference between satisfying a customer or not... but in the world of commercial/industrial it can be several million dollars worth of difference. You either do it right... or don't do it. .

    you're absolutely right.

    guys, is there any online course to study ASHRAE heat load calculation?

  13. #13
    Join Date
    May 2008
    Location
    Ireland
    Posts
    5
    And the type of usage of the building will play a big part

    The last thing you'd wanna do is get it completly wrong......Imagine having to rip it out after people have moved in.....The joys of it all

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