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NEC 110.9 Short-Circuit Current Rating

Discussion in 'Electrical Codes' started by jar546, Feb 7, 2020.

  1. jar546

    jar546 *****istrator

    Oct 16, 2009
    Likes Received:
    We always require AIC ratings from the POCO tranformer to the line side of the service disconnect whenever we have an application to either install or change an electrical service, whether just a meter-base change or service disconnect. This is for residential or commercial with commercial having even more requirements, right down to the permanent labeling of the fault current and date calculated that must be affixed to the service equipment.

    Here is an example of a calculation provided on a set of plans for a new service.

    Does your jurisdiction require this during plan review before the permit is issued? If not, it is always possible that the equipment installed will not be compliant with NEC 110.9 and have to be changed after inspection.

    It is clearly pointed out that the service equipment cannot be a typical 10KAIC as often seen because it would not meet the minimum requirements, especially during a fault condition.
    Annotation 2020-02-07 074550.png
  2. Rick18071

    Rick18071 Sawhorse

    Nov 28, 2009
    Likes Received:
    New commercial plans I see don't have this info and I have to write the requirement on the plans with a red pen. Most of the time the transformer is not there yet for new buildings or it is being changed for existing buildings.
  3. steveray

    steveray Sawhorse

    Nov 25, 2009
    Likes Received:
    And then layer 110.24 on top of that...

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