Grounding vs. Bonding - difference

[inspector23]

I have done two interviews lately, and both asked the same question -
"What is the difference between grounding and bonding?"

I am searching for a short (under one minute) explanation that would convey the difference. I believe the reason for the short answer is that the more clearly you understand the situation, the more concise and targeted you can make the answer.


There seems to be so much BS that floats around on this subject, it makes it hard to give a short, concise answer to a question I admittedly find difficult to answer in such a short amount of time.

Any ideas/suggestions/help?

Thanks -
Mike

 

[roger]

Re: Grounding vs. Bonding - difference

Grounding, the intentional connection to earth.

Bonding, the intentional connection of conductive materials to achieve a equal potential between all. (this does not mean it will be zero potential to earth, take note that in the case of swimming pool bonding earth is of little concern)

Roger

[ May 05, 2005, 09:11 PM: Message edited by: roger ]

 

[bphgravity]

Re: Grounding vs. Bonding - difference

Grounding: A complete waste of time and resources


Bonding: An essential component for a safe installation.


I like Roger's answer and would supplement to say grounding is for the reasons listed in 250.4(A)(1) and bonding is the for the reasons listed in 250.4(A)(4) and (5).

 

[bthielen]

Re: Grounding vs. Bonding - difference

I'm probably going to get beat up for this but perhaps I need an education. I have been taught and consequently believed that the main purpose of grounding was to bond the device to the earth so that in the event of a ground fault to the device, an individual standing on said earth would be at the same potential reference as the device, eliminating voltage difference between the grounded device and the individual. Without a voltage potential difference to force current flow, there is no risk of electrocution.

Bob

 

[tom baker]

Re: Grounding vs. Bonding - difference

BHGravity: Well Put

There is a huge obsession with ground rods when the emphasis needs to be on bonding.

Mike Holt is running a 12 part series in EC&M on Grounding Vs Bonding, started in Jan 2005. EC&M is free. I highly recommend his Grounding Vs Bonding material.

 

[charlie b]

Re: Grounding vs. Bonding - difference

If there is a failure in a device, such that a hot conductor comes in contact with the case, we want there to be a low-resistance path from that case back to the source. This low resistance path will allow a high current to flow, and trip the breaker, thus terminating the event. That is the purpose of bonding: To make sure that any external metal parts with which a human hand might come into contact will not become energized. All such metal parts, all metal that ?might become energized? are connected (i.e., ?bonded?) to each other. Collectively, they form that ?low resistance path? back to the source.

Please note that planet Earth did not come into the above discussion.

I can think of only two reasons for intentionally connecting part of a power system to planet Earth. One is to give a lightning strike a low resistance path to Atlantis. Let the people of Atlantis deal with it. The other is to limit the voltage from any phase conductor to planet Earth to a value that is no higher than the voltage from any phase conductor to the neutral (i.e., ?grounded?) conductor. This is of value because the neutral and the ?low resistance path? discussed above are connected to each other at the main panel. If there is a voltage between that point and planet Earth, then there will be a voltage between anything metal you might touch and the floor beneath your feet.

ASIDE to Bob (bthielen):

That is a common myth. There is some truth to it, and to be honest I cannot tell all of the truth from all of the myth. I can say, however, that current can flow through dirt. If you put your hand on the N-G Bond connection, and your feet on the ground rod, then I think you will have no current flowing through your body. Put your feet a couple feet away from the ground rod, and all bets are off. Think of it this way: as current flows through dirt, it creates a voltage drop along the path, in the same way that voltage drop occurs throughout the length of a conducting wire. If your two feet are spread far enough from each other, the voltage drop (through the dirt) from your left foot to your right foot will force current through your body (translation: ?step potential?). So in reality, along the surface of the planet, there is no such thing as an ?equipotential plane.?

 

[karl riley]

Re: Grounding vs. Bonding - difference

I agree with Charlie's statements.

Since the poster was looking for a short way to say it, I'll try:

Grounding is for the purpose of connecting to earth for lightning discharge and other high voltage discharges.

Bonding is for safety, to allow fault currents to complete the circuit back to the transformer and in the process trip the breaker.

And Bob, please don't try connecting a hot conductor to a ground rod and then touching the ground rod (unless as Charlie says, you are standing on the rod). It will stay at 120V and will not trip the breaker. It could trip your heart, however.

Karl

 

[bthielen]

Re: Grounding vs. Bonding - difference

Thanks for the info.

So then the EGC is not intended to bond the components to earth but to provide an alternate low impedence path back to the source in the event of a ground fault. This would seem to suggest that the terminology and design should change and the EGC should no longer be referred to as a grounding conductor but a bonding conductor.

Am I catching on??

Bob

 

[charlie b]

Re: Grounding vs. Bonding - difference

Yes you are. And there are some who favor replacing the term "Equipment Grounding Conductor" with "Equipment Bonding Conductor." I think it will happen some day.

 

[inspector23]

Re: Grounding vs. Bonding - difference

In this hurry up, time-is-everything-and-we-don't-have-time world, sometimes proper manners and gratitude are casualties.

Thank you all for your insight and help. I really appreciate you help, even if it takes me a couple of days to express it.

 

[pierre]

Re: Grounding vs. Bonding - difference

I am assuming that you are interviewing for a job as an inspector.

I would think you would want to show them how well you understand the industry and the code as it relates to the industry...
To answer your question and keep your answer short and SWEET use the code reference that handles this question very well.


250.4(A)(10, (2) & (3).

Using 1&2 as your answer for grounding, and using 3 as your answer to bonding.

Emphasize connection to earth and limiting/stabilizing voltage for 1&2.

For 3, emphasize- establishes an effective ground fault current path back to the source, to facilitate the opening of the overcurrent device

[ May 07, 2005, 08:33 AM: Message edited by: pierre ]

 

[LarryFine]

Re: Grounding vs. Bonding - difference

Another purpose of the driven and other made grounds is to minimize possible potential differences between accidentally-energized metal equipment and enclosures and that of nearby earth and other conductive surfaces.

 

[charlie]

Re: Grounding vs. Bonding - difference

It is only the guys that are covered by the NEC that are confused over this subject . . . wrong! I was in a meeting last week and one of the guys was talking about just driving a ground rod to "ground" a piece of equipment. I admit that for medium and high voltage, it works but not as well as a solid metal path back to the source.

For what it is worth, it is my understanding that a task group is intending to provide recommendations to change the word grounding to bonding in most places. At that time, we will be identifying the grounding conductor as the bonding conductor. I am looking forward to the 2008 NEC and the 2005 NEC has not been adopted yet by most jurisdictions.

 

[don_resqcapt19]

Re: Grounding vs. Bonding - difference

Has any one read the article titled "Preventing Electrical Shock with Proper Grounding Techniques" in the May/June IAEI magazine? The following statement occurs in the conclusion.

Test the integrity of the grounding system, which includes not only the equipment grounding conductors, but also the ground rod or grounding electrode system. A low impedance path on both of these systems is essential to protect against electrical shock.

I do not agree with the above and a number of other statements made in the article. Doesn't the IAEI review the articles for technical merit before they are published?
Don

[ May 08, 2005, 04:29 PM: Message edited by: don_resqcapt19 ]

 

[charlie]

Re: Grounding vs. Bonding - difference

I asked that same question some time ago to either Phil Cox or Phil Simmons and the response was something like, we have so much material submitted that we make the assumption that the submitter knows what they are talking about. We don't have the time to devote to checking the accuracy of their submittals.

For what it is worth, I tend to agree with the IAEI on this answer (I do not know if they still have the same attitude). Consider the cost of an extra person or two to proof all the submittals for publication. On the other hand, misinformation can be deadly in our field.

 

[iwire]

Re: Grounding vs. Bonding - difference

No information is better than incorrect information from a source that I would have, and I am sure many do take as reliable.

 

[pierre]

Re: Grounding vs. Bonding - difference

If in fact the IAEI does not have the time to peruse the material sent to them, there is a simple solution... don't print!!! There are many who do use this magizine as the gospel and I have seen too many mistakes there in the past.

I do have another solution, but I am not too sure if I should propose it here... but since I am not sure it is wrong I will


Form a committee on this site for review of material - where better than here to put this info in front of a select group to discuss the technical aspects, and only the technical aspects of the pieces.

 

[charlie b]

Re: Grounding vs. Bonding - difference

Originally posted by iwire: No information is better than incorrect information

My wife (the Reference Librarian) would applaud that statement!

 

[bphgravity]

Re: Grounding vs. Bonding - difference

See Below

[ May 09, 2005, 06:40 PM: Message edited by: bphgravity ]

 

[bphgravity]

Re: Grounding vs. Bonding - difference

Did anyone here download the 1884 paper provided by Mr. Holt in a recent newsletter? This paper seems to indicate that grounding of electrical systems came into being as an alternative to providing a return conductor by using the Earth as the return path of current. A few of the current NEC requirements for system grounding are actually suggested in this paper.

It appears to me that grounding resistance is quite important when using a single wire earth return (SWER) system, but even this paper, way back in 1884, indicates that earth resistance is not all that important.