Page 3 of 4 FirstFirst 1234 LastLast
Results 21 to 30 of 38

Thread: panel board as an EGC

  1. #21
    Join Date
    Dec 2012
    Location
    Placerville, CA, USA
    Posts
    17,044
    IMO the fact that under some circumstances the code does not require use of a grounding/bonding bushing or other special hardware to connect a raceway to a box constitutes implicit recognition that the box may then act as part of the EGC path.

    Sent from my XT1585 using Tapatalk

  2. #22
    Join Date
    Aug 2004
    Location
    Northern illinois
    Posts
    14,832
    Quote Originally Posted by infinity View Post
    So you cannot connect an EGC to a metal cabinet or enclosure? Same thing to me.
    you can bond the cabinet with an EGC. I don't see anywhere in 250 where it says you can use the box as part of the EGC though, despite it being a common practice. Normally I would say the code allows you to do whatever is not prohibited but since the code restricts you to using certain things as an EGC, and a metal box is not one of them, I don't see how it is not legalistically a code violation.
    Bob

  3. #23
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    31,314
    Quote Originally Posted by infinity View Post
    You do not need a wire type jumper from EGC bar to EGC bar. When you purchase the listed EGC bar it comes with two screws to connect it to the enclosure that's all that's required. You do not even need to remove any paint the deign of the screws does that for you.
    If you install the bar in a spot designed to install the bar, if installing the bar in some other spot in the panel or even some other manufacturer's bar - you may need to remove paint behind the bar.

    Quote Originally Posted by petersonra View Post
    the screws bond the bar to the box. nothing says that makes the box a legal EGC.

    I am inclined to agree that it is just something that is done but actually not allowed by the code.

    However, for EMT and other metal conduit, the code allows the conduit or EMT to be an EGC. I think you can make a good argument that the UL listing effectively makes the box part of the EGC since the box is part of the conduit/EMT system.

    IMO, as for using an enclosure as an EGC in general, such as the situation the OP mentioned, you don't really have any good argument other than it is a common practice.
    If you have a panel that contains the service disconnecting means and bonding screw installed in the grounded conductor bus, do you make jumpers from the grounded conductor bus to any EGC bars installed in the panel, or are they bonded via the cabinet? Most will say they are bonded via the cabinet and no additional jumpers are needed, if you install additional jumpers then the bonding screw shouldn't be needed, and is one way to do the bonding if you lost the screw.

  4. #24
    Join Date
    Jul 2003
    Location
    New Jersey
    Posts
    22,828
    Quote Originally Posted by kwired View Post
    If you install the bar in a spot designed to install the bar, if installing the bar in some other spot in the panel or even some other manufacturer's bar - you may need to remove paint behind the bar.
    I agree that is why I initially stated the listed EGC bar with its screws from the manufacturer. Any deviation like using a lug or other EGC bar would require the paint to be removed.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  5. #25
    Join Date
    Nov 2010
    Location
    Fort Collins, Colorado
    Posts
    2,365
    Quote Originally Posted by kwired View Post
    If you install the bar in a spot designed to install the bar, if installing the bar in some other spot in the panel or even some other manufacturer's bar - you may need to remove paint behind the bar.

    If you have a panel that contains the service disconnecting means and bonding screw installed in the grounded conductor bus, do you make jumpers from the grounded conductor bus to any EGC bars installed in the panel, or are they bonded via the cabinet? Most will say they are bonded via the cabinet and no additional jumpers are needed, if you install additional jumpers then the bonding screw shouldn't be needed, and is one way to do the bonding if you lost the screw.
    I had this same question as the OP come up the other day and have had this question a number of times. I'm with you, I think a panel used as service equipment illustrates that no jumper would be required between ground bars just like you would not use one in a service rated panel. Another example that illustrates that the enclosure is an EGC is when you need to bond a conduit entry to an enclosure you can use a bonding bushing with a jumper to the enclosure and then continue the conduit out another KO with another bonding bushing and jumper. I think all of these types of examples clearly imply that a metallic enclosure is an approved EGC.

  6. #26
    Join Date
    Feb 2013
    Location
    Aspen, Colo
    Posts
    1,907
    it appears that a screw could be considered a bonding jumper & all terminals are connected to the same metal surface - no bonding between terminals are required IMHO

    250.28 Main Bonding Jumper and System Bonding Jumper.
    For a grounded system, main bonding jumpers and system bonding jumpers shall be installed as follows:
    (C) Attachment. Main bonding jumpers and system bonding jumpers shall be connected in the manner specified by the applicable provisions of 250.8.
    250.8 Connection of Grounding and Bonding Equipment.
    (A) Permitted Methods. Equipment grounding conductors, grounding electrode conductors, and bonding jumpers shall be connected by one or more of the following means:
    (5) Machine screw-type fasteners that engage not less than two threads or are secured with a nut
    (6) Thread-forming machine screws that engage not less than two threads in the enclosure
    CircuitRyder --- Unfortunately not all good ideas are code enforceable.

  7. #27
    Join Date
    May 2011
    Posts
    3,490
    One could argue that a box or the case of a panelboard is a raceway, in which case if your box or panelboard is listed then you can use it as an EGC as long as you don't otherwise violate the listing instructions.

    As for the fact that everyone sometimes uses metal boxes that aren't listed.... Yeah, that's one of those things everybody does even though there isn't a legalistic justification in the code.

  8. #28
    Join Date
    Aug 2004
    Location
    Northern illinois
    Posts
    14,832
    Quote Originally Posted by jaggedben View Post
    One could argue that a box or the case of a panelboard is a raceway, in which case if your box or panelboard is listed then you can use it as an EGC as long as you don't otherwise violate the listing instructions.

    As for the fact that everyone sometimes uses metal boxes that aren't listed.... Yeah, that's one of those things everybody does even though there isn't a legalistic justification in the code.
    where does it say in the code that metal boxes have to be listed?
    Bob

  9. #29
    Join Date
    Dec 2012
    Location
    Denver, Co., U.S.A
    Posts
    16
    I talked to the inspector today about this. He said it is not UL listed to be an EGC.

  10. #30
    Join Date
    Nov 2010
    Location
    Fort Collins, Colorado
    Posts
    2,365
    Quote Originally Posted by JJspark View Post
    I talked to the inspector today about this. He said it is not UL listed to be an EGC.
    Let's look at a garden variety service rated Panel. You put the neutral bond screw in. You install a factory ground bar because you want the extra terminals for equipment grounding conductors (that you could otherwise connect to the neutral bar in this case). Is he the then saying that you need a bonding jumper from the EGC bar to the neutral bar? How would this be any different than the case of multiple EGC bars?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •