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Thread: Opinion of 230.91

  1. #1
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    Opinion of 230.91

    A recent ice storm has brought on a tremendous amount of people (not just electricians) wanting to install generators in every fashion imaginable. I would like to know the opinion of others regarding section 230.91 when a manual transfer switch (SSE) without internal overcurrent protection is retro fitted and mounted back to back to the original service panel that is equipped a with a main overcurrent device. The original panel would no longer be the service panel. Some think that section 230.91 is satisfies because the transfer switch and panel are installed back to back while others think this is a violation because the two panels are separated by the exterior wall. Please let me know your opinion.

  2. #2
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    My opinion is that it would not comply with "immediately adjacent thereto".

    From Merriam-Webster.com:
    adjacent may or may not imply contact but always implies absence of anything of the same kind in between <a house with an adjacent garage>.
    I think it would follow that "immediately adjacent thereto" would not allow the structure of a wall to divide the two.

    Welcome to the forum.

  3. #3
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    Quote Originally Posted by Volta View Post
    My opinion is that it would not comply with "immediately adjacent thereto".

    From Merriam-Webster.com:


    I think it would follow that "immediately adjacent thereto" would not allow the structure of a wall to divide the two.

    Welcome to the forum.

    I absolutely agree with this. Good luck getting anyones attention for this.
    Instructor, Industry Advocate

  4. #4
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    Quote Originally Posted by Mvillines View Post
    The original panel would no longer be the service panel.

    Help me understand this statement.
    1. Does the outside panel count as a "disconnecting means"? That is, will the transfer switch have an "off" position?
    2. Does the outside panel have to be rated as "service equipment"?
    3. Would the N-G bond have to be disconnected in the insider panel, and an N-G bond (with connections to the grounding electrode system) have to be installed in the outside panel?
    4. Would an EGC have to be run between the panels?
    5. Does anyone do any of steps 1-4?
    Charles E. Beck, P.E., Seattle
    Comments based on 2008 NEC unless otherwise noted.

  5. #5
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    Smile

    Quote Originally Posted by charlie b View Post
    1. Does the outside panel count as a "disconnecting means"? That is, will the transfer switch have an "off" position?
    2. Does the outside panel have to be rated as "service equipment"?
    3. Would the N-G bond have to be disconnected in the insider panel, and an N-G bond (with connections to the grounding electrode system) have to be installed in the outside panel?
    4. Would an EGC have to be run between the panels?
    5. Does anyone do any of steps 1-4?
    I do not believe it has to have an off position. A transfer switch does not meet the requirements of 230.82 so it must have a SUSE label if installed in front of service equipment. By doing so, it becomes the service equipment. The grounding must then originate in the new service equipment (the transfer switch) then an EGC does have to be run to the downstream panelboard.

    To answer your last question, probably not. :smile:
    Charlie Eldridge, Indianapolis, Utility Power Guy
    Responses based on the 2011 NEC, unless stated otherwise.

  6. #6
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    Yes Charlie, I totally agree with your post. I am having a problem with “immediately adjacent thereto”. Are we introducing a hazard by adding a transfer switch that is suitable for service equipment (SSE) outside the building, thereby changing the conductors entering the building from service entrance conductors to feeder conductors? I would understand the hazard if the switch was outside and knife blade fuses without a disconnecting means inside.

    There are transfer switches that are designed to be installed between the meter base and meter if installed, and under the control of the serving utility. The code making panel agrees that these switches can be safely used if installed correctly. Does any one see any added hazards by installing the transfer switch outside if the inside OC device also has a disconnecting means such as a breaker? Maybe a good place for a code change?

  7. #7
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    Smile

    Quote Originally Posted by Mvillines View Post
    . . . I am having a problem with “immediately adjacent thereto”. . .
    I think the code means what it says.

    Quote Originally Posted by Mvillines View Post
    . . . Are we introducing a hazard by adding a transfer switch that is suitable for use as service equipment (SUSE) outside the building, thereby changing the conductors entering the building from service entrance conductors to feeder conductors? . .
    Not if the required rewiring is done. This is no different than a room addition on an existing home where the old service is now in the middle of the home. The old service equipment is now a downstream panelboard and must be rewired accordingly.

    Quote Originally Posted by Mvillines View Post
    . . . Does any one see any added hazards by installing the transfer switch outside if the inside OC device also has a disconnecting means such as a breaker? . .
    This is in the purview of the AHJ. :smile:
    Charlie Eldridge, Indianapolis, Utility Power Guy
    Responses based on the 2011 NEC, unless stated otherwise.

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