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Thread: Open Apology

  1. #1
    Join Date
    Mar 2011
    Virginia Beach, VA

    Default Open Apology

    Within the last two weeks or so I posted into a thread that the NEC required load balancing on the bus bars of the service main panelboard.

    Well, I've dug backwards from 2011 through 2002 of code books - Article 408 and cannot not find a supporting statement. So, I apopogize for my error.

    However, if you think of panelboard as a Multiwire Circuit, 2 hot conductors and one shared Neutral then you can understand the benefits of balancing the loads on each bus to take advantage of the shared Neutral.

    How's that for "Justification"?

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  2. #2
    Join Date
    Mar 2007
    Santa Rosa, CA

    Default Re: Open Apology

    Apology accepted.

    And yes, it does make sense. When I worked as an electrician many years ago, the electrical plans for a restaurant specified where to place each circuit and attempted to balance the loads.

    Department of Redundancy Department

  3. #3
    Garry Blankenship's Avatar
    Garry Blankenship Guest

    Default Re: Open Apology

    Your justification is just fine The code and manufacturers pretty much have our backs on load balancing at building service locations. The code requires either the same size neutral wire or at least close to the same size, so even in the unlikely event of substantial imbalance the neutral can carry it. It's next to impossible to create a totally imbalanced load with the landing / termination / circuit breaker locations in a panel alternating as they do. It is utility companies that are concerned about and expert at load balancing. Their goal is to see there is no imbalance and there-by no need for a return conductor, ( neutral wire ), to the dam / gen plant / wind farm etc. In the utility distribution stations, they actually switch phases to correct / eliminate load imbalances. That is a dynamic process dependent upon which supply lines are showing what imbalances at any given time.

  4. #4
    Join Date
    Jul 2008
    Snowbird (this means I'm retired and migrate between locations), FL/MI

    Default Re: Open Apology

    There are circumstances in polyphase service applications where 200% Neutral/bus for imbalance are applicable.

    However on the original post and its historical application, edison type 120/240 service and distribution panel equipment, bus stab ratings and limitations, esp. that pre late 80s equipment, and subsequent are valid qualificiations of the equipment, standards, listing, and limiting restrictions.

    How that could apply to the initial (original, other discussion thread) post and its attached image esp. the quality of the image and equipment depicting, 'twas an unjustified leap, based on the information available (and unlikely, as the equipment doesn't appear obsolete, likely 10k AIC and 15/20 branches appear fully series protected) and nothing suggesting 100% equipment, non-series motor, or anything suggestive of Tsf or poly-phse(usual 80%/125% in 3-wire edison -120/240 Vac 1-Ph, for resi).

    Your local POCO (check their 'green book') may provide specific requirements/restrictions based on their distribution/supply network and regional factors.

    Last edited by H.G. Watson, Sr.; 12-05-2012 at 12:17 PM.

  5. #5
    Join Date
    Oct 2010
    Southwest US

    Default Re: Open Apology

    Apology accepted! Is this part of your 12 steps? If so, glad we could help.


  6. #6
    Join Date
    Aug 2008

    Default Re: Open Apology

    I certainly do not think your belief of something in the NEC that was not there needed an apology, but it does speak to your character as a person. Thumbs up.

    All answers based on unamended National Electrical codes.


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