Re: Adjustment Factors for Conductors with Load Diversity
If, for example, you have 8 wires in a conduit (i.e., two sets of A, B, C, N), and if there is a control mechanism (i.e., an interlock) that allows only 3 of the wires (plus its associated neutral) to carry current at a time, then I believe you can simply say that the number of current-carrying conductors is 3, and not 6. You would not have to correct per Table 310.15(B)(2)(a). But that has nothing to do with “load diversity.”
The phrase “diversity factor” (ASIDE: Is that the same thing as “load diversity”? I do not know.) is defined as “The ratio of the sum of the individual maximum demands of the various subdivisions of a system to the maximum demand of the whole system.” If anyone can figure out how to apply this definition in a useful way (i.e., to get more ampacity out of an installation), then I would love to hear about the method.
To Steve66: Regarding your “what if?” situation: The difference between the number (or total rating) of the circuits you install, as compared to the VA per square foot allowance that 220 requires us to include, is unrelated to “diversity factor,” as defined above. But no knowing what is meant by “load diversity,” I can’t comment on your “what if.”
Charles E. Beck, P.E., Seattle
Comments based on 2008 NEC unless otherwise noted.