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Thread: Service Conductor tap inside Main Panel

  1. #1
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    Service Conductor tap inside Main Panel

    I have a job where the electrician tapped the main service conductors from the transformer inside of an MDP. The reason for the tap was to go from (3) conductors per phase to (2) because there were only two lugs inside the MDP.

    This panel has a 600A main inside of it acting as the main disconnect for the whole building and also has other over-current devices for HVAC equipment. The closest code section that I could find is 312.8 which it seems to meet this criteria but im questioning it because they are service conductors being tapped within this panel.

    Any other code sections that visit this more specifically?

    (Job Permitted Under NEC 2011)

    Picture Attached.

    Thanks!
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  2. #2
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    The word tap has a specific meaning in Article 240. This is not a tap it's more like a splice. From the photo it appears that you have the applicable code section.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  3. #3
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    Quote Originally Posted by infinity View Post
    The word tap has a specific meaning in Article 240. This is not a tap it's more like a splice. From the photo it appears that you have the applicable code section.
    Agree, splice is more appropriate. Thanks for the quick response!

  4. #4
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    not sure about code but I thought that 600 frame size had 3 lug/ph
    apparently so did the guy who pulled the wire

  5. #5
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    Quote Originally Posted by Ingenieur View Post
    not sure about code but I thought that 600 frame size had 3 lug/ph
    apparently so did the guy who pulled the wire
    Yes - I was under that impression also. Makes me think a 400A panel was installed instead of a 600A. I will definitely be checking that tomorrow.

  6. #6
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    Quote Originally Posted by Ingenieur View Post
    not sure about code but I thought that 600 frame size had 3 lug/ph
    apparently so did the guy who pulled the wire
    There often multiple options of the breaker lugs on that size of breaker...you just have to specify the correct ones when you order the panel. That being said, the correct lugs would be available and it probably would have been a more cost effective, but maybe not timely, fix to the issue.
    Don, Illinois
    (All code citations are 2017 unless otherwise noted)

  7. #7
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    Quote Originally Posted by don_resqcapt19 View Post
    There often multiple options of the breaker lugs on that size of breaker...you just have to specify the correct ones when you order the panel. That being said, the correct lugs would be available and it probably would have been a more cost effective, but maybe not timely, fix to the issue.
    new lugs for the cb are not usually stocked at the local supply house but the connectors are.
    Bob

  8. #8
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    Quote Originally Posted by infinity View Post
    The word tap has a specific meaning in Article 240. This is not a tap it's more like a splice. From the photo it appears that you have the applicable code section.
    Not even in 240 in general if so we would likely have a 240.2 definition. Mostly the meaning only applies to 240.21.
    I live for today, I'm just a day behind.

  9. #9
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    Quote Originally Posted by Npstewart View Post
    I have a job where the electrician tapped the main service conductors from the transformer inside of an MDP. The reason for the tap was to go from (3) conductors per phase to (2) because there were only two lugs inside the MDP.

    This panel has a 600A main inside of it acting as the main disconnect for the whole building and also has other over-current devices for HVAC equipment. The closest code section that I could find is 312.8 which it seems to meet this criteria but im questioning it because they are service conductors being tapped within this panel.

    Any other code sections that visit this more specifically?

    (Job Permitted Under NEC 2011)

    Picture Attached.

    Thanks!
    Might look a little like someone didn't plan very well, but as long as there is enough space to comply with 312.8 nothing wrong with it.

    I believe if you don't order that Square D breaker with optional lug provisions, you get ones that accept two 500 (maybe 600) conductors per terminal. Is usually least cost to order lug options at same time you order the panel/breaker/branch breakers/cabinet/ cover all on one order. If you change your mind after but want to connect it immediately - something like done in that picture is likely the fastest way to get it working.
    I live for today, I'm just a day behind.

  10. #10
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    I would have done one thing differently: placed the line conductors in holes 1,3, and 5, and the jumpers in 2 and 4.

    Just the symmetrical gremlin inside me.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

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