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

  1. #61
    Join Date
    Feb 2003
    Location
    Maryland
    Posts
    310

    Back to the 2 basic issues as I see them.

    Quote Originally Posted by docj67 View Post
    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 Attachment 19283Attachment 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....Attachment 19285
    Within the scope of the OP's post that I have copied above are two issues that I have not seen clearly addressed as yet. The first is that the Service Disconnecting Means (SDM); which here consists of 4 separate Service Equipment Enclosures (SEE) does no appear to have a Grounding Electrode Conductor (GEC) installed. To correct this you check the Size of the GEC which is required by the sizing of the Service Entry Conductors. In your case that is #6 AWG Cu or #4 AWG Al. As of 2014 NEC the GEC must be installed in accordance with NEC 250.64(D)(3):

    "250.64 Grounding Electrode Conductor Installation.
    Grounding electrode conductors at the service, at each building or structure where supplied by a feeder(s) or branch circuit(s), or at a separately derived system shall be installed as specified in 250.64(A) through (F).
    (D) Building or Structure with Multiple Disconnecting Means in Separate Enclosures. For a service or feeder with two or more disconnecting means in separate enclosures supplying a building or structure, the grounding electrode connections shall be made in accordance with 250.64(D)(1), (D)(2), or (D)(3).
    (3) Common Location. A grounding electrode conductor shall be connected in a wireway or other accessible enclosure on the supply side of the disconnecting means to one or more of the following, as applicable:
    (1) Grounded service conductor(s)
    (2) Equipment grounding conductor installed with the feeder
    (3) Supply-side bonding jumper

    The connection shall be made with exothermic welding or a connector listed as grounding and bonding equipment. The grounding electrode conductor shall be sized in accordance with 250.66 based on the service-entrance or feeder conductor(s) at the common location where the connection is made."

    The second thing that is not clear is if the feeder supplied panels (Commonly called Sub Panels) that are located in the interior of the unit have carefully separated Grounded Current Carrying Conductors (Usually called neutrals) and EGCs. In both the Square D Homeline panel, that is to remain, and in the new panel, that will replace the existing Federal Pacific Electric panel, the "neutral" conductors and the EGCs must be electrically separated and attached only to the corresponding conductor of the Feeder.

    If the OP confirms or corrects those 2 problems then he can walk away with a clear conscience.

    There is another land mine here in addition to the possibility that additional loads may have been added so as to possibly overload the Service Entry Conductors. Land mine number 2 is that If all 4 of those Service Equipment Enclosures is not fitted with a single Main Disconnecting Means then the number of throws of the hand required to disconnect the service may now exceed the maximum number allowed for a single service.
    Tom Horne

    "This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison

  2. #62
    Join Date
    Jul 2017
    Location
    Berkeley California USA
    Posts
    64

    update and thx for latest reply

    Zero: Each disconnect has an GEC that appear to be be bonded to 4 AWG inside building under customer's Homeline panel that then lands on a water pipe buried in concrete that matches one of the 6 valid NEC grounding electrode types.

    First, no additional load was added to SEC's, as was mentioned several times earlier in the thread, thread is dense so I can see it's easy to miss this important point!
    job was like for like subpanel replacement and refeed with EGC as per

    "(B) Conductors of the Same Circuit. All conductors ofthe same circuit and, where used, the grounded conductorand all equipment grounding conductors and bonding con-ductors shall be contained within the same raceway, auxil-iary gutter, cable tray, cablebus assembly, trench, cable, orcord, unless otherwise permitted in accordance with300.3(B)(1) through (B)(4)."

    and like for like replace FP disconnect with modern one.

    Second,
    both subpanels do have separated egcs and neutrals

    Third, work passed inspection but a second grounding
    electrode was ordered installed as we could only
    find one--mentioned above.

    This leaves the issue of the oddity of the egcs in the customers
    homeline subpanel.

    The customer and his wife are Berkely PHD's in Astrophysics
    and Chemical Engineering and have been thoroughly briefed on the ground issues.

    My understanding of the 6 throws rule is
    it applies to single services not a group of
    4. It
    sounds like there is something here?

    i also discovered in the course of work on the project that all the circuits from the old fp panel were using egcs to other means.... ie not thru the fpe panel. The customers are well aware of this but not interested in correcting it at this time.
    I
    moved those circuits to the new subpanel which has a proper egc to the new main disconnect
    i installed. These circuit feeders are all old cloth romex sans EGC.

    Thx for the feedback!






    Quote Originally Posted by hornetd View Post
    Within the scope of the OP's post that I have copied above are two issues that I have not seen clearly addressed as yet. The first is that the Service Disconnecting Means (SDM); which here consists of 4 separate Service Equipment Enclosures (SEE) does no appear to have a Grounding Electrode Conductor (GEC) installed. To correct this you check the Size of the GEC which is required by the sizing of the Service Entry Conductors. In your case that is #6 AWG Cu or #4 AWG Al. As of 2014 NEC the GEC must be installed in accordance with NEC 250.64(D)(3):

    "250.64 Grounding Electrode Conductor Installation.
    Grounding electrode conductors at the service, at each building or structure where supplied by a feeder(s) or branch circuit(s), or at a separately derived system shall be installed as specified in 250.64(A) through (F).
    (D) Building or Structure with Multiple Disconnecting Means in Separate Enclosures. For a service or feeder with two or more disconnecting means in separate enclosures supplying a building or structure, the grounding electrode connections shall be made in accordance with 250.64(D)(1), (D)(2), or (D)(3).
    (3) Common Location. A grounding electrode conductor shall be connected in a wireway or other accessible enclosure on the supply side of the disconnecting means to one or more of the following, as applicable:
    (1) Grounded service conductor(s)
    (2) Equipment grounding conductor installed with the feeder
    (3) Supply-side bonding jumper

    The connection shall be made with exothermic welding or a connector listed as grounding and bonding equipment. The grounding electrode conductor shall be sized in accordance with 250.66 based on the service-entrance or feeder conductor(s) at the common location where the connection is made."

    The second thing that is not clear is if the feeder supplied panels (Commonly called Sub Panels) that are located in the interior of the unit have carefully separated Grounded Current Carrying Conductors (Usually called neutrals) and EGCs. In both the Square D Homeline panel, that is to remain, and in the new panel, that will replace the existing Federal Pacific Electric panel, the "neutral" conductors and the EGCs must be electrically separated and attached only to the corresponding conductor of the Feeder.

    If the OP confirms or corrects those 2 problems then he can walk away with a clear conscience.

    There is another land mine here in addition to the possibility that additional loads may have been added so as to possibly overload the Service Entry Conductors. Land mine number 2 is that If all 4 of those Service Equipment Enclosures is not fitted with a single Main Disconnecting Means then the number of throws of the hand required to disconnect the service may now exceed the maximum number allowed for a single service.
    Last edited by docj67; 02-07-18 at 05:18 PM. Reason: correction 2

  3. #63
    Join Date
    Jul 2017
    Location
    Berkeley California USA
    Posts
    64

    Reply 2: Supply side bonding jumper and EGC

    After rereading I interpret this to mean that the service taps and meter can array ( supply side ) should have an EGC and bonding jumper to EGC which then goes to grounding electrode array. I did not open all of this equipment but I would guess that it does not. As per bold below. Is this correct?

    250.64 Grounding Electrode Conductor Installation.
    Grounding electrode conductors at the service, at each building or structure where supplied by a feeder(s) or branch circuit(s), or at a separately derived system shall be installed as specified in 250.64(A) through (F).
    (D) Building or Structure with Multiple Disconnecting Means in Separate Enclosures. For a service or feeder with two or more disconnecting means in separate enclosures supplying a building or structure, the grounding electrode connections shall be made in accordance with 250.64(D)(1), (D)(2), or (D)(3).
    (3) Common Location. A grounding electrode conductor shall be connected in a wireway or other accessible enclosure on the supply side of the disconnecting means to one or more of the following, as applicable:



    Quote Originally Posted by docj67 View Post
    Zero: Each disconnect has an GEC that appear to be be bonded to 4 AWG inside building under customer's Homeline panel that then lands on a water pipe buried in concrete that matches one of the 6 valid NEC grounding electrode types.

    First, no additional load was added to SEC's, as was mentioned several times earlier in the thread, thread is dense so I can see it's easy to miss this important point!
    job was like for like subpanel replacement and refeed with EGC as per

    "(B) Conductors of the Same Circuit. All conductors ofthe same circuit and, where used, the grounded conductorand all equipment grounding conductors and bonding con-ductors shall be contained within the same raceway, auxil-iary gutter, cable tray, cablebus assembly, trench, cable, orcord, unless otherwise permitted in accordance with300.3(B)(1) through (B)(4)."

    and like for like replace FP disconnect with modern one.

    Second,
    both subpanels do have separated egcs and neutrals

    Third, work passed inspection but a second grounding
    electrode was ordered installed as we could only
    find one--mentioned above.

    This leaves the issue of the oddity of the egcs in the customers
    homeline subpanel.

    The customer and his wife are Berkely PHD's in Astrophysics
    and Chemical Engineering and have been thoroughly briefed on the ground issues.

    My understanding of the 6 throws rule is
    it applies to single services not a group of
    4. It
    sounds like there is something here?

    i also discovered in the course of work on the project that all the circuits from the old fp panel were using egcs to other means.... ie not thru the fpe panel. The customers are well aware of this but not interested in correcting it at this time.
    I
    moved those circuits to the new subpanel which has a proper egc to the new main disconnect
    i installed. These circuit feeders are all old cloth romex sans EGC.

    Thx for the feedback!
    Last edited by docj67; 02-07-18 at 05:25 PM. Reason: addition 2nd correction

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