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    Demand - diversity factors

    We are beginning work for a new client - fitness centers - and we are wondering if anyone is familiar with any NEC code language that would allow us to take a reduced demand or diversity load on large groups of electrically-powered same-type fitness equipment (similar to the demand factors for commercial kitchen equipment when there are 6 or more pieces of cooking equipment). We have not seen anything in the code.

    The specific question is this - the fitness center has as many as 20 to 30 treadmills, each requiring a dedicated 20 amp circuit (equipment nameplate says FLA = 16 at 120 V). From experience, we have rarely (or never) seen all of the treadmills operating at one time, and anticipate that even if every one were operating, they would likely not all be operating at maximum speed. That being the case, we are wondering if we are permitted to take a reduced load for the combined equipment at the feeder or service level, while still providing individual 20 amp circuits to each piece of equipment.

    Any help or thoughts would be very much appreciated.

    #2
    The NEC does not define diversity. In fact, I'm almost certain that word does not appear in the NEC.

    Do the treadmills plug into receptacles?

    To me, you are dealing with Receptacle loads in other than dwelling units which is covered by 220.44. You might be able to convince the AHJ that table 220.44 applies, which is first 10 kVA at 100% demand factor, remaining kVA at 50%. But he/she might decide that 220.50 applies since treadmills presumably have at least one motor and must be calculated in accordance with 430.24, 25 and 26. So 430.24 or 25 unless the AHJ gives permission to use 430.26.

    Using 220.44 and assuming 30 treadmills at 100% FLA (16A):
    30 x 120 x 16 = 57,600 kVA

    First 10 kVA + 0.5 x 47,600 = 33,800 kVA

    That's 281 Amps for the receptacle loads.

    Not sure how much you can shave from that trying to apply 430.26.

    I don't know if you ever been to Orange Theory, but around here that place is PACKED. Every single unit can be used during a popular class and some time of that session can potentially be spent at 100%.

    I would advise two things. First get in touch with the AHJ and talk it through with them. Make your case and see what they say. If they insist on a particular method, your hands might be tied. Second, see if you can somehow get your hands on historical data as the information note in 430.26 suggest. Does the owner have other location with the same setup? If so, what is the max demand according to the utility?

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      #3
      they are receptacle-connected and we thought of the 50% above 10 KVA - but the snag we see is article 220.14(A) since those receptacles are outlets for a specific "appliance" or other load. that section excludes such receptacles from the demand load reduction. what you are saying is more or less what we came up with also. thanks.

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        #4
        Originally posted by rlqdot View Post
        they are receptacle-connected and we thought of the 50% above 10 KVA - but the snag we see is article 220.14(A) since those receptacles are outlets for a specific "appliance" or other load. that section excludes such receptacles from the demand load reduction. what you are saying is more or less what we came up with also. thanks.
        This could be helpful: LINK
        It says, gymnasium demand factor = 70 to 75%; load factor = 20 to 45%.

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          #5
          Originally posted by topgone View Post
          This could be helpful. It says, gymnasium demand factor = 70 to 75%; load factor = 20 to 45%.
          That link takes you to a document that has no meaning in our industry. It does not supersede the NEC. More to the point, it does not apply to the facilities for which the vast majority of forum members spend our work days. I am an exception to that rule; I am able to use the information discussed in that document. That is because I work for the US Army Corps of Engineers, and my projects are all on US Military bases. These projects are required to be designed and installed in accordance with the United Facilities Criteria (UFCs). You can find them at www.wbdg.org. The document from the link is nothing more than a restatement of UFC requirements and allowances. I have the ability to apply a 70 - 75% demand factor for a gym, if and only if that gym is located on a military base. That would not help the OP


          Charles E. Beck, P.E., Seattle
          Comments based on 2017 NEC unless otherwise noted.

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            #6
            Originally posted by rlqdot View Post
            they are receptacle-connected and we thought of the 50% above 10 KVA - but the snag we see is article 220.14(A) since those receptacles are outlets for a specific "appliance" or other load. that section excludes such receptacles from the demand load reduction. what you are saying is more or less what we came up with also. thanks.
            Reading it back again, 220.44 applies only with 220.14(H) and (I). I would amend my remarks to say 220.14(A) applies.

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              #7
              Originally posted by Non-Sequitur
              Never understood why treadmills have motors instead of generators.
              Alternate current
              Line to ground and ground to line
              Current alternates

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