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  1. #1

    Commercial HVAC sizing - Simple Estimation possible?

    Hi there,

    I am a computer science student engaged in project pertaining to HVAC systems. I have little understanding of these systems but am reading extensively, trying to learn.

    I am required to create an application to estimate the size of a commercial HVAC compontent. This means calculating heat/cooling load. I am aware the manual N procedure for commercial calculations, but I am no engineer and am having a little difficultly making sense of it, and cannot afford to buy books on it.

    However since I only need an estimation, I am looking for a rule-of-thumb calculation for commercial spaces, could anyone possibly provide me with something like this, or link me to a resource?

    I have come accross articles explaining various methods, but they are uncited... http://www.openxtra.co.uk/articles/c...ting-heat-load

    How accurate are these methods, and where are their numbers coming from?

    I hope this question is not HVAC sacrilege, but any help in this regard would be extremely appreciated I am in Dublin, Ireland if climate is relevant.

  2. #2
    Join Date
    Jun 2010
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    Philadelphia PA
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    2,190
    Use my profile and we can "talk" off line.
    A little too much for this forum
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  3. #3
    Apologies, I could not for the life of me figure out how to write on your profile, not the usual v-bulletin it seems, or perhaps its my sleep deprevation :P

    Thank you for your answer, I have come across such load calculations in the mean time (which I will post shortly), please provide info if you can though :]

    However, It seems in my investigation I have neglected AHUs (Air Handling Units). As far as I can tell, these seem to be an all in one HVAC. Would you know of a calculation for the average size required (capacity) for these units? and perhaps an efficiency rating/method? I have been looking, but information is harder to find for these systems.

    I have found: http://www.engineeringtoolbox.com/ai...ate-d_882.html
    Would this m^3/s or air change rate represent simple capacity requirements for an AHU? Would you have information on these units?

    Also, how can one tell when a HVAC component needs replacing?

    Cheers, hope you can help :]

  4. #4
    Join Date
    Aug 2007
    Location
    Winter Haven, FL
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    4,367
    The only thing i have ever seen to be somewhat reliable, is cubic feet x .075. Then divideby 400. Should put you somewhere in range for a commercial office or retail space.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,913
    Quote Originally Posted by Joe Harper View Post
    The only thing i have ever seen to be somewhat reliable, is cubic feet x .075. Then divideby 400. Should put you somewhere in range for a commercial office or retail space.
    Probably not real close. Most retail has a fair gain from glass, and customers coming in and out of the entrance, along with the large load from the customers being in the store/retail space.

    Commercial office space usually has a fair amount of load from equipment.

    Both have fresh air requirements which adds to the load. Plus retail has a large load from lighting.
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  6. #6
    Join Date
    Aug 2007
    Location
    Winter Haven, FL
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    4,367
    Quote Originally Posted by beenthere View Post
    Probably not real close. Most retail has a fair gain from glass, and customers coming in and out of the entrance, along with the large load from the customers being in the store/retail space.

    Commercial office space usually has a fair amount of load from equipment.

    Both have fresh air requirements which adds to the load. Plus retail has a large load from lighting.
    I should have specified. The above method would only be somewhat (if at all) applicable on a structure under 5000 sqft. Its more of a quicke for a tech on a poor cooling call. There is no substitute for a proper heat load calculation.

  7. #7
    Join Date
    Sep 2008
    Location
    Western PA
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    ntopliffe

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