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Watts per square foot rules of thumb

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    Watts per square foot rules of thumb

    Realizing full well, that laboratories come in a wide variety of types and therefore electrical loading, if at the initial stages of a project, you were trying to take a preliminary shot at what the electrical demand load would be, in what range of watts per square foot would you guess?
    Mike Shields, PE
    Boston, MA

    #2
    I’ve wired a couple of analytical laboratories, you can’t generalise on loading. Two 25kW calcining furnaces switching in and out sends the total current draw haywire.

    All I’ll say is find out what the specific loads are and work from there.
    The reports of my death are greatly exaggerated.

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      #3
      When I don't know any better, I guess at 20 VA/sq-ft throughout the building for an overall conservative demand load for the service.
      Ron

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        #4
        Originally posted by mshields View Post
        Realizing full well, that laboratories come in a wide variety of types and therefore electrical loading, if at the initial stages of a project, you were trying to take a preliminary shot at what the electrical demand load would be, in what range of watts per square foot would you guess?

        With the disclaimer that there isnt really a "correct" answer due to many variables, I would say Ron is right on. I have done a lot of work in a 17,000 sq foot lab, three floors, one floor is offices, other two are all labs. They have tons of self contained refrigerators and freezers and thus lots of HVAC cooling. They have 4 10KW autoclaves, but not other single significant loads. The max demand per the utility is about 162 KVA or 9.5 VA/sq foot. Service size is about 21 VA/sq foot. I havnt done a formal NEC calc for the facility, but did for a similar one, and I think a calc would be a bit more, probably in the mid to high 20's.
        Ethan Brush - East West Electric. NY, WA. MA

        "You can't generalize"

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