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Thread: Odd intriguing and perhaps dangerous multi unit grounding question/problem: JUMPER??

  1. #1
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    Odd intriguing and perhaps dangerous multi unit grounding question/problem: JUMPER??

    Oh mighty gurus: I have the following scenario:

    A 4 unit condo has a 4 tapped gutter from one main service drop providing 4 services/disconnects. I have been hired and maybe soon to be fired, to replace a FED Pacific subpanel in a closet in one unit and replace the FP disconnect. This unit has another newer subpanel installed by the prior owner /contractor /builder. I discovered early on that the the ground bar of this newer panel has TWO #8 GEC"S attached to it.

    It was brought to my attention early on in the project; I was originally hired for data work , that there were 4 ground wires going into my customer's unit--this came up when he mentioned the possible FP replacement project.

    I discovered that the 4 ground wires into his unit were in fact the 4 ground wires from the 4 units disconnects--they go into his unit right under the prior mentioned newer subpanel

    The customer's unit has two 50 amp 240 feeds for the two subpanels---one is FP and has no ground and is slated for replacement, the other is new. Today I stopped by the unit bc I suddenly realized there was no recollection on my part of whether I had seen a GEC for newer subpanel. BC this is my first permitted / to be inspected job, I have been sweating bullets. I looked in the FP disconnect and saw NO ground from the newer subpanel.

    My assumption is that the the 1.25 inch feeder for the subpanel feed was used as ground, as all circuits on that newer subpanel have "valid" grounds.

    If this is true then it means that likely the 2 #8's on that subpanel bar are main grounding connectors from other unit's services!!!

    My sense is not to proceed w work until this is resolved.

    I'd like to request feedback on hazard potential of such an odd grounding scenario, or maybe I'm losing my mind and it's legit.

    If it is UNLEGIT, I'd like to know as much as possible, or if more info is needed, I may be interested in any experts in
    grounding in Northern Calif who maybe avail for hire.

    Then there's the main building ground: I don't have the test equipment to see if the apparent bond to a waterpipe of all 4 units meets 25ohms NOR whether there is the second Grounding Electrode present.

    Thx so much!

    Newbie_Nate

  2. #2
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    First off I think we ought to get the right terminology so we know exactly what it is you are asking. The grounding electrode conductor is the wire that goes from the neutral bar (or wherever the grounded conductor is connected to Earth) to the grounding electrode system..

    Equipment grounding conductors are the green wires that connect all the metal parts of the system together that are not electrically energized.

    There are also bonding conductors that connect the various grounding electrodes together to form a grounding electrode system.

    I don't believe there's any prohibition in a code that says you can't connect equipment grounding conductors from one unit to another.

    I don't even recall that there is any prohibition on running grounding electrode conductors through one unit to get to another unit. I'm not entirely sure you're allowed to use a ground bar in a panel to connect multiple grounding electrodes together though but I think you could use the neutral bar for such a purpose.
    Bob

  3. #3
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    What the heck! Don’t yell at me, I did not do it. I swear!

    So, I am intriguing and dangerous, I thought I was just nuts.
    "Electricity is really just organized lightning." George Carlin


    Derek

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    reply to Bob

    Thx for the reply: What can I clarify in my use of terminology?

    Multiple service grounds are possibly connected to a subpanel from another service

    Please detail what I can clarify.

    thx!


    Quote Originally Posted by petersonra View Post
    First off I think we ought to get the right terminology so we know exactly what it is you are asking. The grounding electrode conductor is the wire that goes from the neutral bar (or wherever the grounded conductor is connected to Earth) to the grounding electrode system..

    Equipment grounding conductors are the green wires that connect all the metal parts of the system together that are not electrically energized.

    There are also bonding conductors that connect the various grounding electrodes together to form a grounding electrode system.

    I don't believe there's any prohibition in a code that says you can't connect equipment grounding conductors from one unit to another.

    It seems to me that most likely the place where the grounding electrode conductor is terminated would be at the service Point outside.

  5. #5
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    Quote Originally Posted by docj67 View Post
    Thx for the reply: What can I clarify in my use of terminology?

    Multiple service grounds are possibly connected to a subpanel from another service

    Please detail what I can clarify.

    thx!
    What do you mean by Service ground? Is this the grounding electrode system, the grounding electrode conductor, or an equipment grounding conductor?

    The term Service ground does not have a defined meaning
    Bob

  6. #6
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    "We have met the enemy and they are us" - Pogo. I use this in my grounding and bonding classes. We are confused on grounding and bonding as we tend to use "ground" for different functions.
    Mike Holt once said (for grounding) what color is it and what does it do?
    Moderator-Washington State
    Ancora Imparo

  7. #7
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    reivisted job site: here are some pics and hopefully this makes my q clearer.....

    It's likely that at least ONE Grounding Electrode Conductor from one unit's main panel is bonded to ground bar in another unit'subpanel. All 4 units are tapped from one feed from Pacific Gas and Electric. Building ground electrode is most likely not up to code and I have recommended to client that we simply redo the building ground to code. This would involve removing that ( or those ) #8(s) from my customer's sub panel. The Subpanel ground appears to be done with the RMC or EMT used to run the subpanel feed from Click image for larger version. 

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Name:	mutipleGECuptocustunitunderpanel.jpg 
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ID:	19284 is service, as there is no discrete wire from that panel coming in to the main panel.

    This all began when the customer showed me inspection report questioning why 4 #8's go into his unit. I traced them back and found they were the 4 service Grounding Electrode Conductors....
    Click image for larger version. 

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ID:	19285

  8. #8
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    The whole set up is a little too muddled for me to understand what is going on.

    I will just say the if these are (main) GECs, what I assume you were calling service grounds, and land in sub panels then you have violations of 250.24(A)(1).

    If these GECs are going to auxiliary electrodes then it could be legal, this assumes building has a proper GES to start with.
    "Electricity is really just organized lightning." George Carlin


    Derek

  9. #9
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    Thx J

    If they do land on other subpanel bar in fact and i ve yet to prove that conclusively, that would be violating as you say

    250.24(A)(1).

    If that is the case is there a risk for unpredictable behavior in subpanel if say there's a ground fault incoming to the subpanel?

    Also this scenario if true has a ground loop between customer service and subpanel.....

    going to recon
    250.24(A)(1).

    THX !!

  10. #10
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    250.24(A)(1).

    My interpretation is that it would be a violation BC it does not bond directly to building electrode.

    Care to shed some wisdom from this scenario if true relative to 250.24(A)(1).?

    thx!

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