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Grounding Sub Panels

| Posted in General Discussion on February 23, 1999 10:54am

*
Scooter,

It would appear that the inspector is actually asking you to create a Code violation instead of alleviating one.

NEC (1999) Article 250-50:

“Interior metal water piping located more than 5 ft (1.52m) from the point of entrance to the buliding shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are a part of the grounding system.” (emphasis added)

The whole concept of grounding the sub-panel is to treat it such that all grounds are potentially the same reference point. Adding a third ground path hardly seems an appropriate way to accomplish this.

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  1. simon | Feb 27, 1999 05:40am | #4

    *
    SSSSSSSSHHHHHH! Don't tell 'em I said so, but you can argue with city hall (and win); I see it all the time. Inspectors are NOT always right, they are human too. Some of them just seem to get more annoyed when they are wrong than you do.

    There are volumes to be written here, but not by me!

  2. Guest_ | Feb 27, 1999 05:51am | #5

    *
    Something that seems to work for me Scooter, is to simply ask the inspector to show you that section of the Code Book that he's refering to, so that you can be better informed of course.

    Regardless of where in North America you are working, the applicable code book must be used. If he can't clearly demonstrate the offence, there isn't one.

    1. Guest_ | Feb 27, 1999 08:49am | #6

      *I had a similar electrical project, wiring my barn 75' from the house. An electrician told me I had to run ground wires back to the service panel in the house. I didn't think that could be right so I called the state and they told me local codes cannot exceed state codes and that state code required in such a situation two ground rods a minimum of 6' apart from an unspliced wire. But I guess the question posed isn't one of wiring but of building inspectors. If only they were as easy to figure out as wiring is.

      1. Guest_ | Feb 28, 1999 04:14am | #8

        *Scooter, Our inspectors insist on grounding to an underground copper water line if it is available within a "reasonable" distance simply because it makes such a superior grounding electrode compared to a rod. It sounds to me like you have done that in the main panel and then run a grounding wire connected to the main grounding bar out to the garage. Is that correct? If so, your method is how they want it done around here.My only other comment is that we are required to use #4 grounding wire on 200 amp services and not run anything smaller than # 6 unprotected to other panels.We had an inspector here some years back that insisted on grounding (bonding) PVC conduit, so you do get some strange ideas out of some of these fellows!

  3. Guest_ | Feb 28, 1999 04:14am | #7

    *
    OK. Here's the beef I have with the inspector. I installed a new 200 amp service panel, fully grounded per code, which is double grounded: (1) copper rod pounded into the ground; and (2) An a pipe clamp attached to the incomming water main 5' into the house. The clamp is attached to unbroken 8 guage grounding cable that goes from the pipe to the ground rod and then UNSPLICED to the service panel. There is no splice in the ground cable at all, even though it makes a stop at the ground rod.

    We've installed a 60 amp subpanel for the customer in a garage, with 8 guage wire, including a ground into the panel. I also grounded the panel with a copper rod.

    The darn inspector wants me to repeat the ground from a cold water pipe into the subpanel. The nearest cold water pipe is, of course, in the home 30' away.

    The inspector is new, and before I get really pissed at this guy, I'd like to know if I am wrong. Since the main box is grounded, and the ground goes to the subpanel, and it is grounded again with a rod, any more is overkill. But you can't argue with city hall.

    Thanks.

    1. Guest_ | Feb 23, 1999 07:39am | #1

      *Scooter, tell him* to read Article 250 of the NEC, including all exceptions. 250-32, 250-50, 250-52,250-64 all deal with your situation.*Well, maybe ask would be better... and you should read it first.

      1. Guest_ | Feb 23, 1999 09:43am | #2

        *I take it the garage is detached from the house? And no water service is expected to go to the garage? If so, I go with George and read NEC section 250 for the choices other than cold water pipe.

        1. Jim_Haynes | Feb 23, 1999 10:54pm | #3

          *Scooter,It would appear that the inspector is actually asking you to create a Code violation instead of alleviating one. NEC (1999) Article 250-50:"Interior metal water piping located more than 5 ft (1.52m) from the point of entrance to the buliding shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are a part of the grounding system." (emphasis added)The whole concept of grounding the sub-panel is to treat it such that all grounds are potentially the same reference point. Adding a third ground path hardly seems an appropriate way to accomplish this.

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