Code Q-Ambiguous ???

[pattbaa]

I'm baffled by a Code-question which I perceive to be ambiguous----

Q------"The conductor (that) connects the metal of equiptments and other enclosures to the System Grounded Conductor (Neutral) and/or the Grounding Electrode Conductor at the Service equiptment is the -----"

(A) Equiptment bonding-jumper
(B) bonding-jumper
(C) equiptment-grounding conductor
(D) grounded conductor

The question is specific on a connection to the System Grounded Conductor at the Service.

The "Main Bonding Jumper" is defined as "The connection between the Grounded Circuit Conductor and the Equiptment Grounded Conductor at the Service"

Please Advise-----

 

[charlie b]

Re: Code Q-Ambiguous ???

Originally posted by pattbaa: The "Main Bonding Jumper" is defined as "The connection between the Grounded Circuit Conductor and the Equipment GROUNDED (my emphasis, the NEC definition has the word ?Grounding? here) Conductor at the Service"

I agree that the question is not worded as well as it could be. But I would not call it ?ambiguous,? for that word implies that the question could be interpreted in more than one way. The only way to get from an enclosure to the service panel is via the Equipment Grounding Conductor, and that is the right answer to the only way to interpret the question. Once you are inside the service panel, the Main Bonding Jumper connects the EGC and the Grounded Conductor to each other. The GEC connects to one or another of these two points.

 

[Ed MacLaren]

Re: Code Q-Ambiguous ???

I think I would go with answer (b) because the question specifies a conductor "at the service equipment".

Ed

 

[charlie b]

Re: Code Q-Ambiguous ???

But it also says that it connects the enclosures of equipment to the service panel. Those enclosures could be a couple hundred feet away, and the bonding jumper is not that long. The EGC does have one termination point in the service panel, but it is the only conductor under discussion that has a termination point at the equipment. I will stand by my answer of (C).

 

[don_resqcapt19]

Re: Code Q-Ambiguous ???

The question is very poorly worded, and in my opinion the correct answer is not shown. The answer should be "main bonding jumper". I also agree with the original posted that the question is ambiguous as it is not clear if the equipment in question is service equipment or other equipment. Per 250.28, the main bonding jumper connects the EGCs to the grounded conductor at the service equipment.
Don

 

[charlie b]

Re: Code Q-Ambiguous ???

Several of us are seeing different things in the question. The only thing we agree on is that the question is poorly worded.

Please let me point out that the question is not asking about connecting the neutral to the ground wire. It is asking about connecting the metal enclosures of equipment to the neutral. That tells me that the answer must involve a termination at the equipment. The question also includes an ?or? statement that asks about connecting the metal enclosures of equipment to the ?grounding electrode conductor? ? the one that goes from the service panel to the ground rod. Neither a bonding jumper nor "The Main Bonding Jumper" terminates at the metal enclosures of equipment. The only thing that does this job is the EGC.

That, at least, is how I see the (poorly worded) question.

 

[pattbaa]

Re: Code Q-Ambiguous ???

Reffering to "Equiptment-Bonding Jumpers", "Bonding-Jumppers",and "Equiptment Grounding Conductors" when discussing Grounding connections at the Service between the metal of enclosures, the Grounding Electrode Conductor, and the Grounded Service Conductor is "mixing apples and oranges"

The basic purpose of an EGC is to conduct the Fault-Currents of Branch-Circuits and Feeders "back to the source,i.e., the Grounded Circuit Conductor.This requires a direct connection between the EGC and the "Neutral", not the Grounding Electrode Conductor. (refered to in the Q)

The EGC of a Branch-Ciruit supplied from a panel in a "detached" structure could conduct a Fault-Current back to the Grounded Feeder Conductor, not the Service Conductor, in certain installations. In discussing EGC's, on must distinguish between their application; Feeder, Branch-Circuit, specific equiptments, etc.

Art. 250.28 reads----"A Main Bonding Jumper shall connect the Equiptment Grounding Conductor(s) to the Grounded Service Conductor within each Service Dis-Connect"

Art. 250.92 (A), "Bonding of Services reads----"Metal parts indicated shall be Bonded together"---"raceways, gutters, enclosures,---" A conductor so used would be a "Bonding Conductor", not a EGC.

3 "Exhibits" (illustrations) in the NEC "Handbook" illustrate Service Grounding connections between the "metallic surfaces", the Grounding Electrode Conductor, and the Grounded System Conductor. All 3 indicate "Bonding-Jumpers" but none indicate an EGC.

 

[charlie b]

Re: Code Q-Ambiguous ???

It seems to me that you are saying, in part, that the phrase ?and/or the Grounding Electrode Conductor? adds nothing to the question, causes confusion, and should have been removed from the question. I agree.

But now I perceive another source of confusion, and it relates to the English language, not to the code. Delete the phrase mentioned above, and what is left in the question matches the following pattern: ?The conductor that connects ?A? to ?B? at location ?C? is called ____. Our language would require the preposition ?at? to refer back to the thing immediately preceding it, not to something far earlier in the sentence. The thing that is located at ?C? (the service panel) is the ?B? thing (the neutral), not the ?A? thing (the enclosures). Here is the difference:

The question does not say, ??connect the metal of equipments and other enclosures (meaning the enclosure of the service panel itself) to the neutral (located at the Service Panel).? If it did, the answer would be Main Bonding Jumper.

The question does say, ??connect the metal of equipments and other enclosures (such as the case of a motor located out in the facility somewhere) to the neutral (located at the Service Panel).? That answer is the EGC.

 

[Ed MacLaren]

Re: Code Q-Ambiguous ???

I don't really see much wrong with the question, except a few typos. If one is looking for perfect grammar and syntax, I suspect that many such questions could be suspect.

Paraphrasing, it says - "The conductor that connects ------- equipment ----- enclosures to the System Grounded Conductor (Neutral) and/or the Grounding Electrode Conductor at the Service equipment is the -----"

The "and/or" statement is technically correct if ungrounded three phase, three-wire systems are to be considered, because, in such systems the equipment enclosures are bonded (by the main bonding jumper) to the Grounding Electrode Conductor (GEC) only.

I agree that (the correct) Response (B) should read - "Main bonding jumper".

Ed

[ October 16, 2003, 10:53 PM: Message edited by: Ed MacLaren ]

 

[eprice]

Re: Code Q-Ambiguous ???

Take a look at the definition of "Grounding Conductor, Equipment" in section 100. It is very similar to the wording of the question. The question may not be worded the best, but I'm with Charlie, the answer is C.