Grounding Electrode System Question

[mbrooke]

Dave

I do realize that no one likes change for changes sake. We should have a pretty good reason for changing a long used term especially if it changes the meaning of the new language. Bonding is different from grounding but if you look at the reason for grounding electrical wiring I suspect that you might agree that the "Equipment Grounding Conductors" do not have a roll in Grounding per se. The fact that they are connected to the Grounded Current Carrying Conductor (GCCC) and the Grounding Electrode Conductor at the Service Disconnecting Means (SDM) is what led us to call it a Grounding Conductor in the first place. If you look at it objectively I think that you will see that the EGC's main purpose is to connect the non current carrying but conductive parts of the electrical system to the GCCC of the Service Entry Conductors so as to provide a low impedance path back to the source of the current in the secondary of the Utility's supply transformer. If there were no GEC connected to the the electrical system at all the EGCs could still perform that job. That is why some of us are asking why the industry and the section 250 Code Making Panel continue to call it a grounding conductor when that is not the function that it is installed to perform. It's essential role is to rapidly conduct any current flowing on the non current carrying conductive portions of the electrical system back to the current source so that that flow will briefly exceed the designed opening current of the Over Current Protective Device (OCPD). The more quickly the escaped current is returned to it's source the faster the OCPD will open and the less damage there will be to the electrical system and the less likely a "fire of electrical origin" will be. Without the EGC to send that leaking current back home to it's transformer the opening of the OCPD will not only be slower it is not likely to occur at all. What the conductor which we presently call the Equipment Grounding Conductor does is it connects all of the non current carrying conductive parts of the electrical system to the GCCC (Neutral) of the service conductors. Let me repeat that if I somehow manage to leave out the installation of a Grounding Electrode System so that there is no connection between the electrical system and ground a properly installed EGC will still provide an effective low impedance fault current path back to the source. What it is doing is not Grounding. That conductor bonds all of that conductive electrical system parts to each other and to the Neutral of the Service Conductors. That is why some of us want to see that name changed to reflect what the conductor is installed to do. We think that what is presently called the EGC would be more accurately called an Equipment BONDING Conductor. Further we believe that a more functional naming of that conductor will lessen the amount of confusion that presently exists both within the industry and amongst the public would not occur as readily.

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Tom Horne

Agree.

It is source loop conduction which protects life and property. Grounding and bonding is merely secondary after the fact when one looks at the theory.

 

[mbrooke]

You can call an EGC whatever you want, how about Protective Earth like they do in Europe? Thirty years from now we are going to have the same issues no matter what these components of the electrical system are called because it is not the nouns that are the problem it's a lack of understanding of electrical systems. Switching the language to equipment bonding conductors confuses things because not all bonding conductors are meant for fault clearing.

I propose calling it "protective conductor"

Dropping bonding, grounding, and earth from its name will end confusion as neither of any three protect life and property and typical electrical systems. Ultimately (I think) a clear picture will come to the industry when a 3rd pillar is added to article 250: source loop conduction or (SLC).

 

[hornetd]

I propose calling it "protective conductor"

Dropping bonding, grounding, and earth from its name will end confusion as neither of any three protect life and property and typical electrical systems. Ultimately (I think) a clear picture will come to the industry when a 3rd pillar is added to article 250: source loop conduction or (SLC).

I'll have to think about this suggestion. I suspect that many folks here would object to adding a new term to the code. Based on the reception of the idea on a couple of other Electrician message boards I thought that using the term Equipment Bonding Conductor might be a remedy to what appears to me to be a lot of confusion about what it is intended to do. Now I find that there is resistance to any change in the language and that some of that resistance is quite strident. I certainly never intended to wind folks out the way my support of that idea has.

It has been argued, both here and elsewhere, that the name Bonding Conductor has to be reserved for the Main Bonding Jumper. I don't see why since a few electrical system types don't even have a Main Bonding Jumper. One example of that is the ungrounded Delta secondary supplied systems that are used in SOME manufacturing operations which produce large conductive assemblies, such as ships and airplanes. Another use of these systems is to power critical equipment such as the refrigeration of dangerous pathogens at a research lab. But I have to admit that in those cases the conductors which connect all of the non current carrying conductive parts of the electrical system back to the Service Disconnecting Means could only Ground those system parts since there is no service conductor to which to connect them. In that case they would definitely be Equipment GROUNDING Conductors.

As a total aside we did try to get an change order to install a Ground Detector on that pathogen refrigeration supplies Service Disconnecting Means but our offer to propose on it was rejected for reasons unknown to me. That was three decades ago so it presumably is ~10 editions of the US National Electric Code (NEC) ago. I looked at the code language on ungrounded Delta systems a couple of days ago. Be aware that the newest version which I still have on hand is the 2014 as I retired 5 years ago and even just the code itself is kind of expensive on a retiree's income. I didn't have time to study that section really thoroughly but at first reading it looks like the NEC now requires a Ground Detection System to be installed on ungrounded systems. I just want to say I really like the inclusion of a mandatory requirement for ground detection because the absence of one always seemed dangerous to me. I always suspected that no matter how careful we were that there would eventually be a ground fault to one of the phases and it would remain that way until a ground fault occurred on a different phase. My concern is that since neither of those ground faults would necessarily be a low impedance one that the possibility of a burn down due to prolonged arcing was raised to too high a likelihood.

--
Tom Horne

 

[mbrooke]

I'll have to think about this suggestion. I suspect that many folks here would object to adding a new term to the code. Based on the reception of the idea on a couple of other Electrician message boards I thought that using the term Equipment Bonding Conductor might be a remedy to what appears to me to be a lot of confusion about what it is intended to do. Now I find that there is resistance to any change in the language and that some of that resistance is quite strident. I certainly never intended to wind folks out the way my support of that idea has.

I support a language change 10,000%. In addition to re-writing all of article 250.

Unfortunately many individuals are strongly against any type of code change as I've gradually found out that individuals begin to distance themselves from you or begin to call your theory/experience into question. The idea is to discredit the voice of change, even if that voice is for the betterment of the trade. I am fully for the individual electrician, technician and engineer.

It has been argued, both here and elsewhere, that the name Bonding Conductor has to be reserved for the Main Bonding Jumper. I don't see why since a few electrical system types don't even have a Main Bonding Jumper. One example of that is the ungrounded Delta secondary supplied systems that are used in SOME manufacturing operations which produce large conductive assemblies, such as ships and airplanes. Another use of these systems is to power critical equipment such as the refrigeration of dangerous pathogens at a research lab. But I have to admit that in those cases the conductors which connect all of the non current carrying conductive parts of the electrical system back to the Service Disconnecting Means could only Ground those system parts since there is no service conductor to which to connect them. In that case they would definitely be Equipment GROUNDING Conductors.

I, IMO, would not use the word bonding conductor to describe an EGC. In my view bonding is merely connecting two or more pieces of metal together. This in of itself does not eliminate danger as 1) the size of the danger relative to remote earth is only increased 2) voltage drop along the impedance of the bond wire creates differences of potential 3) bonding energizes more parts making a single unbonded object with a reference to remote earth more hazardous (think pool ladder where one handle is bonded and the other is disconnected from the bonding grid)

That is not to say bonding has no merit.

However, what removes touch potential in both grounded and ungrounded systems is high circulating current between any two secondary terminals of the serving transformer in series with an OCPD.

As a total aside we did try to get an change order to install a Ground Detector on that pathogen refrigeration supplies Service Disconnecting Means but our offer to propose on it was rejected for reasons unknown to me. That was three decades ago so it presumably is ~10 editions of the US National Electric Code (NEC) ago. I looked at the code language on ungrounded Delta systems a couple of days ago. Be aware that the newest version which I still have on hand is the 2014 as I retired 5 years ago and even just the code itself is kind of expensive on a retiree's income. I didn't have time to study that section really thoroughly but at first reading it looks like the NEC now requires a Ground Detection System to be installed on ungrounded systems. I just want to say I really like the inclusion of a mandatory requirement for ground detection because the absence of one always seemed dangerous to me. I always suspected that no matter how careful we were that there would eventually be a ground fault to one of the phases and it would remain that way until a ground fault occurred on a different phase. My concern is that since neither of those ground faults would necessarily be a low impedance one that the possibility of a burn down due to prolonged arcing was raised to too high a likelihood.

--
Tom Horne

Indeed. However, even with a ground detector one must always consider a second fault that could occur between orderly shut down.

Theoretically the circuit protective conductor and phase conductors in an ungrounded system should be sized for a circuit disconnection time twice a fast as that for a solidly grounded system in that fault current must travel from faulty circuit #1 through its CPC, to the CPC bar, into the CPC of the second faulty circuit and then up into its hot conductor before heading back to the source. The fault loop impedance is technically doubled.

Every circuit breaker has a minimum admittance value as determined by its worse case maximum clearing time.