wording of article 250-54

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curious george

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In the '99 NEC (which, incidentally, our city still enforces - sadly) article 250-54 deals with supplementary grounding electrodes. The last portion of the sentence states "but the earth shall not be used as the sole equipment grounding CONDUCTOR.

After referring to definitions, to my way of thinking this should read sole equipment grounding ELECTRODE.

Since there is no way to connect the earth to the areas described in definitions for GEC, I am thinking this should be stated as the electrode; ie:, just laying a bare conductor in a trench in the ground, where the earth is used as the electrode.

The 2002 NEC reads the same way as far as this sentence is concerned, but I am not aware of the 2005 NEC wording.
Your thoughts would help - thanks!
 
Re: wording of article 250-54

This sentence was revised for the 2005 cycle to read, in part: " the earth shall not be used as an effective ground-fault current path as specified in 250.4(A)(5) and 250.4(B)(4)."

Essentially, this means that your supplemental electrode needs to be bonded to the main electrode.
 
Re: wording of article 250-54

Originally posted by bdarnell:
This sentence was revised for the 2005 cycle to read, in part: " the earth shall not be used as an effective ground-fault current path as specified in 250.4(A)(5) and 250.4(B)(4)."

Essentially, this means that your supplemental electrode needs to be bonded to the main electrode.
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He not talking about a supplemental electrode he asking about a supplementary ground electrodes and is does not have to be bonded to the main electrode
 
Re: wording of article 250-54

Originally posted by curious george:. . . to my way of thinking this should read sole equipment grounding ELECTRODE.
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The Earth is never an "electrode," so it cannot have been intended that way. All it is saying is that you cannot rely on planet Earth as the only path to get fault current back to the source (i.e., to force the breaker to trip, thereby terminating the fault).
 
Re: wording of article 250-54

Maybe I mispoke. 250.54 deals with Supplementary Grounding Electrodes. This paragraph requires that the earth not be used as the sole return path. I agree that you do not have to install a supplementary electrode in the same manner as the main GEC required in 250.50, however, you do have to connect the supplementary electrode to the grounding electrode at the source. Otherwise, what is your return path ?
 
Re: wording of article 250-54

All this section is stating is that an equipment grounding conductor needs to be installed and connected to the equipment. Some manufacturers try to indicate that their equipment needs a separate ground and some electricians interperate this to mean that it should be isolated from the premises grounding system. This section clearifies that if a grounding electrode is installed at equipment, it can't be used as an EGC.

Supplementary grounding electrodes serve no purpose and it shouldn't be asumed that they can.
 
Re: wording of article 250-54

Originally posted by bdarnell:
Maybe I mispoke. 250.54 deals with Supplementary Grounding Electrodes. This paragraph requires that the earth not be used as the sole return path. I agree that you do not have to install a supplementary electrode in the same manner as the main GEC required in 250.50, however, you do have to connect the supplementary electrode to the grounding electrode at the source. Otherwise, what is your return path ?
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Well let me ask you this if I did not use a supplementary electrode what would be my return path?

A supplementary electrode is just that. It's not needed as far as i am concerned.
 
Re: wording of article 250-54

Originally posted by bphgravity:
... some electricians interperate this to mean that it should be isolated from the premises grounding system.
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I can remember reading field installation instructions from one of the large office equipment manufacturers (I won't mention the name, but it starts with "X") which directed the electrician to install an isolated, dedicated ground, connected to nothing else. Basically, they wanted a ground rod outside connected just to their equipment. The factory tech would not do the install unless it was done this way. Thank goodness that has gone away, but, sadly remnants of that thinking remain.
 
Re: wording of article 250-54

Well let me ask you this if I did not use a supplementary electrode what would be my return path?

A supplementary electrode is just that. It's not needed as far as i am concerned.
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I agree. It's not needed. All I'm trying to say is that if you install one, for whatever reason, and ground your widget with it, you also have to have an effective return path and the earth can't be that path.

Sorry if I wasn't clear.
 
Re: wording of article 250-54

Also some phone companies wanted it that way to.

When some of the computer people want it that way even today I say no problem I will add as many supplementary grounds you want but it has nothing to do with the wiring of his power system. It has nothing to do with nothing but if it makes them happy and they don't mind paying the tab then no problem.
 
Re: wording of article 250-54

I believe the supplementary electrodes are for eliminating any voltage potentials that my exist between the equipment and its IMMEDIATE surroundings. We had a job several years ago where the customer claimed to be getting shocked by an old steel light pole. The customer wanted us to diagnose and fix the problem. All conductors were in good shape as well as the grounding conductor. As it turns out, the pole had no supplementary electrode and was next to a high tension power line. We installed a supplementary ground rod and conductor and the problem went away. Static electricity build-up can be the death of some computer equipment components and boards. This has nothing at all to do with clearing faults.
 
Re: wording of article 250-54

If connected to a properly sized EGC, static nor induced voltage will / should be present. Explain how sticking a conductor in the Earth corrected the problem? :confused:
 
Re: wording of article 250-54

Originally posted by bphgravity:
If connected to a properly sized EGC, static nor induced voltage will / should be present. Explain how sticking a conductor in the Earth corrected the problem? :confused:
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By bringing the pole and the surrounding earth to the same potential, whether at 0 volts or not. Think equipotential grid.
 
Re: wording of article 250-54

Larry,
By bringing the pole and the surrounding earth to the same potential, whether at 0 volts or not. Think equipotential grid.
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That is not really possible by the use of a ground rod. It may be possible, to some extent, if you use a closely spaced grip under the earth, but a rod cannot accomplish that because the earth is not a good enough conductor. The rod could provide some reduction in potential in a small area very close to the rod, but ~70% of the voltage is dropped in the first 12" around the rod. If you are touching the earth more than 12" from the rod and the energized pole, you will be subjected to at least 70% of the pole to earth voltage.
Don
 
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