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Thread: Unfamiliar w/ Particular Requirement by Building Department

  1. #1
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    Unfamiliar w/ Particular Requirement by Building Department

    Hi,

    I am designing a commercial, rooftop PV system, and we will have to do a line-side tap on a commercial switchboard.

    The building department wrote me that the switchboard w/ the tap installed has to be re-certified by a 3rd-party and designed by an electrical engineer.

    I understand the second part --that as they want an electrical PE to stamp the plans, but what do they mean about re-certification of the switchboard w/ the tap installed? How do I even start that process? Who would I go to? Sounds expensive!

    Thanks in advance!

    Kind Regards,
    Andy

  2. #2
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    Because you are modifying something that is UL listed and tested in a particular configuration

    https://services.ul.com/service/fiel...ction-service/
    Ron

  3. #3
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    Not sure how much you know about the specifics, If you have had your eyes on it, but I wonder if there is an option of changing out the lugs for ones approved by the manufacturer that would meet your needs. Maybe they will go easier on you if its all "approved" stuff. If the switchboard has metering provisions, then yeah thats not going to work as you would be forced to hit the bussbars. I have had to do such a thing a few times, but have always gotten lucky and the AHJ says just use listed lugs and dont drill holes and you're fine.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  4. #4
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    HERE is a link to a white paper written by UL that addresses tapping of buses in Switchboards and Panelboards.

    Panelboards and deadfront switchboards are not Listed to have their busbars tapped unless there are existing holes in the busbars marked with the word “Tap” adjacent to the holes. Other holes in the busbar that are not marked with the word “Tap” are intended for the connection of overcurrent devices, other device’s as identified by the product markings and in the installation instructions or other uses identified by the manufacturer.

    When the electrical equipment Listing does not include product markings or instructions for tapping busbars this should be treated like any other modification of a Listed Product. That would require a field evaluation of the busbar tap.

    You would want to contact a Certified Field Evaluation Body to perform a Field Evaluation.

    UL can provide field evaluations, if you are interested in more information regarding UL's field evaluations please PM me.

    Chris

  5. #5
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    Quote Originally Posted by andrew.tkelly View Post
    Hi,

    I am designing a commercial, rooftop PV system, and we will have to do a line-side tap on a commercial switchboard.

    The building department wrote me that the switchboard w/ the tap installed has to be re-certified by a 3rd-party and designed by an electrical engineer.

    I understand the second part --that as they want an electrical PE to stamp the plans, but what do they mean about re-certification of the switchboard w/ the tap installed? How do I even start that process? Who would I go to? Sounds expensive!

    Thanks in advance!

    Kind Regards,
    Andy
    Will the AHJ allow you to connect to the service conductors on the line side of the switchboard OCPD inside the enclosure via insulation piercing connectors? Most that we deal with will allow it.

  6. #6
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    Quote Originally Posted by ggunn View Post
    Will the AHJ allow you to connect to the service conductors on the line side of the switchboard OCPD inside the enclosure via insulation piercing connectors? Most that we deal with will allow it.
    Yeah that's what I was thinking, lugs or tap onto conductors. I don't see how they can require recertification or even engineer approval for that. Isn't that what we have electricians for?
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  7. #7
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    Quote Originally Posted by electrofelon View Post
    Yeah that's what I was thinking, lugs or tap onto conductors. I don't see how they can require recertification or even engineer approval for that. Isn't that what we have electricians for?
    Most commercial PV systems here in Texas are required by AHJ's to carry a PE stamp on the plans. It's not related to the method of interconnection.

  8. #8
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    Thanks for the all the info, guys. I just got off the phone with UL's program manager of field evaluations. They said they can send a field inspector to certify it for somewhere between $3-5k. That's not as bad as I thought it would be.

    As far as using insulation piercing conductors to connect to the line side of the service entrance conductors, I will ask the AHJ.

  9. #9
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    Also, just for own learning, it seems there are four ways to connect in a switchboard:

    1. Have the inverter output circuit protected by OCPD in the switchboard
    2. Do a line-side tap on the switchboard's busbar (usually has to be inspected by a NRTL field inspector)
    3. Use insulation piercing conductors on the service entrance conductors on the line-side of the switchboard OCPD
    4. ...and something about lugs? Can someone explain in detail about replacing the lugs to connect PV?

    If there are any other ways of interconnecting on a commercial switchboard, please let me know just for the sake of knowledge. Thank you!

    Andy

  10. #10
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    Quote Originally Posted by andrew.tkelly View Post
    Thanks for the all the info, guys. I just got off the phone with UL's program manager of field evaluations. They said they can send a field inspector to certify it for somewhere between $3-5k. That's not as bad as I thought it would be.

    As far as using insulation piercing conductors to connect to the line side of the service entrance conductors, I will ask the AHJ.
    Your post sort of implies a large service which likely means parallel conductors. If you have parallel service conductors tapping them can become very complicated and expensive as all the conductors of each phase would have to be tapped as one.

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