Residential Electric Panel Grounded at Meter Not at Panel?

Discussion in 'Electrical Forum discussion & Blog' started by molo, Mar 31, 2021.

  1. molo

    molo Member

    Joined:
    Sep 23, 2006
    Location:
    Cold New York
    Is it acceptable/sufficient to have a residential electric service with one ground going from the panel to the copper water line, and the other ground going from a ground rod to the electric meter box?
    If so, can both grounds be grounded at the electric meter box, thus avoiding the need to run a ground to the indoor breaker panel?

    Thank you in advance for any replies!
     
  2. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    A few points:

    The "grounds" you are referring to are properly called Grounding Electrode Conductors, or GECs. They are a bit different than the typical ground run with a circuit, the Equipment Grounding Conductor, or EGC.

    If your copper water line is buried outside for at least 10', then it is a grounding electrode, and you need to connect a GEC to it within 5' of it entering the building. If the buried metallic portion is less than 10', then it is not a grounding electrode, and you instead run a bonding jumper to the metallic water piping system, anywhere along its length. In either case you jumper across any short non-metallic breaks, e.g. dielectric fittings at a water heater.

    1 ground rod alone, or 1 ground rod and a water pipe electrode, is not sufficient for the NEC. You need to add a 2nd ground rod, or another electrode like a Ufer (concrete encased electrode, foundation ground).

    At the service the GECs terminate to the grounded (neutral) service conductor. This can be anywhere from the weatherhead (for an aerial service) to the main service disconnect, or in between. Connecting them at the meter is at discretion of the utility, and practice varies by region; some utilities prohibit it, some expect it.

    One GEC has to be unspliced, e.g. a continuous copper conductor from the grounding electrode to the grounded service conductor. If you have one unspliced GEC, then you can have splices in any of your other GECs. That means if your unspliced GEC is as large as your other GEC or bonding jumper, you can just bring the latter to the unspliced GEC and connect them together. Note that the required size for a GEC to a water pipe electrode (or I think for a bonding jumper for a water piping system) depends on the service size and may be larger than the minimum allowable size for the GEC to a ground rod (which need not exceed #6 Cu)

    So if your utility permits it, and your water pipe is a grounding electrode, you can bring both GECs to your meter. You can also just bring your water pipe GEC or bonding jumper to anywhere on the the GEC to your ground rod, as long as the latter is as large as as the water pipe connection.

    Cheers, Wayne
     
  3. Sponsor

    Sponsor Paid Advertisement

     
  4. molo

    molo Member

    Joined:
    Sep 23, 2006
    Location:
    Cold New York
    Thank you very much for the detailed reply. Forgive my lack of familiarity with the terminology. In a residential service is the ECG included in the cable that connects the meter to the panel? And am I interpreting it correctly, that it is acceptable to not have a GEC directly to the panel if other means of ground, such as water pipe and ground rod both connected to meter, are provided?
     
  5. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    The EGC system originates in the main service panel and is used for downstream bonding. The service panel has the unique EGC-neutral bond in the system, which means that if an EGC gets energized by an ungrounded conductor, the circuit is completed and the breaker should trip. Downstream of the service panel there should never be a neutral-EGC (ground) connection. Upstream of the main panel, there is no EGC, and the neutral conductor itself is used for bonding.

    So no, there is no EGC between the meter and the service panel, just the two ungrounded conductors (for single phase) and the neutral. The meter can is bonded to the neutral.

    If your utility allows the GEC(s) to go to the meter can and land there, yes, there need not be any GECs going to the service panel.

    Cheers, Wayne
     
  6. mikha'el

    mikha'el Member

    Joined:
    Jan 27, 2015
    Location:
    Texas
    Most utilities don't want any grounds entering the meter can.
    It creates a parallel path - if you lost the neutral the (much smaller) ground wire would take its place, and no one would be the wiser until something burned up.
     
    Stuff likes this.
  7. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    I think this has more to do with concern that allowing access to the meter can could facilitate illegally tapping the service before the meter, rather than due to parallel neutral paths. Bringing a GEC to the neutral in the meter can would only create a parallel path if other grounding electrodes are brought to the service disconnect, and those other electrodes having a bonding jumper to the electrodes brought to the meter can. And lots of allowable or required practices on the utility side of the service disconnect create parallel neutral paths--for example any time a separate meter can and service disconnect are connected via metallic conduit.

    Cheers, Wayne
     
  8. WorthFlorida

    WorthFlorida The wife is still training me.

    Joined:
    Oct 28, 2009
    Occupation:
    Retired
    Location:
    Orlando, Florida
  9. mikha'el

    mikha'el Member

    Joined:
    Jan 27, 2015
    Location:
    Texas
    Last edited: Apr 15, 2021
  10. mikha'el

    mikha'el Member

    Joined:
    Jan 27, 2015
    Location:
    Texas
    Perhaps - though now if you have a "smart" meter they'll know if you've pulled it.
    It does differ from one POCO to another.
    Oncor here doesn't allow it (edit - they'll allow you to run it through the meter can, but not terminate).
    Can't recall PSE (Seattle) but I'm pretty sure you always took it to the service disconnect.
     
    Last edited: Apr 15, 2021
Similar Threads: Residential Electric
Forum Title Date
Electrical Forum discussion & Blog DIYer's doing residential electrical repairs/installs before Sep 16, 2010
Electrical Forum discussion & Blog What is the new year bringing, especially in residential, especially in service panel Jan 5, 2014
Electrical Forum discussion & Blog Residential Lights and Outlets on Same Circuit? Aug 23, 2010
Electrical Forum discussion & Blog PVC conduit for residential install Sep 8, 2008
Electrical Forum discussion & Blog Residential Wiring & Crimp Fittings Jul 22, 2007

Share This Page