Is there an international standard that specifies the size of the grounding conductor to bond a metallic part of the installation to a grounding bar?.

And to connect the grounding bar to the grounding rod?.

By "installation" I mean any metallic stuff such as the steel structure of the building, the case of an electrical panel, and so on.

  • What's the difference between grounding bar and grounding rod?
    – Federico Russo
    May 2, 2012 at 13:52
  • 1
    @FedericoRusso - I think it's safe to presume that this is an electrical panel which will contain a rectangular bar with holes and screw clamps. A wire runs from this bar to a long copper rod which is physically pounded into the dirt (aka 'ground'). The question is about the appropriate sizing of these bars, rods, and wires. For example, a typical 60A residential panel in the US requires a 10-gauge wire, and a 100A panel requires an 8-gauge per the US National Electrical Code. No idea about international standards, though. May 2, 2012 at 15:01
  • 2
    No international standards, follow the electric code for your region/
    – Steven
    Jul 1, 2012 at 19:32

2 Answers 2


If you are in the US, you'll likely follow National Electrical Code (NEC).

Lets start with some definitions.

NEC 2008

Bonding Jumper, Main. The connection between the grounded circuit conductor and the equipment grounding conductor at the service.

Grounding Conductor. A conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes.

Grounding Conductor, Equipment (EGC). The conductive path installed to connect normally non–current carrying metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor, or both.

Grounding Electrode. A conducting object through which a direct connection to earth is established.

Grounding Electrode Conductor. A conductor used to connect the system grounded conductor or the equipment to a grounding electrode or to a point on the grounding electrode system.

and a picture to help make things a bit more clear.

enter image description here

The size of the Main Bonding Jumper, Grounding Electrode Conductor, and Grounded Electrode is defined by table 250.66

NEC Table 250.66

The size of Equipment Grounding Conductors (the ones that run from the Ground bus bar out with each circuit), is defined by table 250.122.

NEC Table 250.122


There are various international standards that are trending towards "homologation" or which are being reissued under other standard numbers with no technical changes. BUT what applies currently varies by country and as grounding bars and rods all lead to ground in the country where the installation is (with a few very very unusual exceptions)(CERN would be interesting :-)) you need to check the regulations in the country of interest.

  • Hi @Russell, thanks for your post. any idea of which applies to USA?
    – miguelao75
    May 4, 2012 at 13:17

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