Diversity Factor VS. Demand Factor

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charlie b

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Lockport, IL
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Retired Electrical Engineer
I think the biggest difference between the two terms is that the NEC uses "demand factor" and does not use "diversity factor." It does mention "load diversity," but it is not clear whether that is the same thing.

The NEC allows us to size services and feeders at a smaller size than would be needed to simultaneously supply every single item that is installed in the building. The NEC recognizes that not everything will be running at its full rated load at the same time. For example, if a restaurant has 8 items of permanently connected (i.e., hard wired) kitchen equipment, then Table 220.56 allows us to only count 65% of the total load of these items. That is a "demand factor."

As another example, Table B.310.15(B)(2)(11) gives us a method of calulating ampacities under certain conditions that include "load diversity." But the NEC never defines the term "load diversity," and we are left to wonder if it is intended to mean the same thing as "diversity factor." That later term is well defined in electrical engineering textbooks (I have one at my desk that includes that definition). The link that kingpb gave you explains the definition of "diversity factor." I just don't know if it is at all useful in NEC load calulations.

For my part, in an effort to maintain clarity through the precise and correct use of terminology, I would prefer that members of our industry stop using the phrase "diversity factor" completely. It really doesn't often affect anything we do.
 

Smart $

Esteemed Member
Location
Ohio
FWIW, there is only one section in the entire Code which actually permits adjustment using load diversity... and that is the application of Table 520.44.

Article 520 is for THEATERS, MOTION PICTURE AND TELEVISION STUDIOS, AND SIMILAR LOCATIONS.
 
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