If we use that approach then all conductors of a grounded system are "connected" to earth... :blink:
Grounding VS Bonding
- Thread starter RB1
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- Windsor, CO NEC: 2017
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- Service Manager
Ungrounded systems even.
jwelectric
Senior Member
- Location
- North Carolina
All except the ungrounded conductors, you know the ones that gets fuses or breakers
jwelectric
Senior Member
- Location
- North Carolina
And even this systems has equipment grounding conductors that are not bonded to a grounded conductor so how could the equipment grounding conductor of this system be called the bonding conductor?
- Location
- Windsor, CO NEC: 2017
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- Service Manager
Because 250.4(B)(3) says that's what it's for?
Wait, I bowed out of this one.
Wait, I bowed out of this one.
- Location
- Windsor, CO NEC: 2017
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- Service Manager
Actually, they are connected to ground when a load is applied.
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- Placerville, CA, USA
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- Retired PV System Designer
I think that both common usage and NEC usage support your sense of "connected", and I do not think that more than a few people will argue with that. But in common usage, not modified by any contradictory definition in the NEC, the two word phrase "directly connected" means something different.
And in both common and NEC usage, there is also the concept that two thing (neutral wire set and EGC wire set) can be connected in more than one place, but generally should not be.
So when I ask whether the neutral and ground buses are connected in a subpanel, I am most likely asking whether there is a direct connection within that panel rather than whether they are indirectly connected somewhere else.
One word that perhaps helps us work around this is "bonded". If I say that two wires are bonded at the subpanel, I am less likely to be misinterpreted to be referring to an indirect connection somewhere else in the wiring system.
- Location
- Illinois
- Occupation
- retired electrician
But they are not directly connected to the transformer. Even the code looks at that way. The code tells us there is no direct electrical connection between the grounded conductor of a 480/277Y system and the grounded conductor of a 208/120Y system that is supplied from the 480 volt system. If you use your idea of "connected" there would be no such thing as a SDS.
My head does not need any clearing. I know what the code says and means.
I am very well aware of what the code says. There is nothing there that tells me to define connected like you want to define it.
All I know is what I see in the field, even on design documents where people think that all you have to do to make the EGC to work is to connect it to the earth because that is what the term tells them to do.
In talking with instructors of the Canadian Electrical Code, where they eliminated the term Equipment Grounding Conductor a number of years ago and replaced it with Equipment Bonding Conductor, they tell me that that change made it a lot easier to teach the point of what the equipment bonding conductor is doing. They no long have people thinking that they can make the equipment safe by connecting it to the earth. They more clearly understand that the equipment bonding conductor is the fault clearing path.
- Location
- Illinois
- Occupation
- retired electrician
So branch circuits are not connected to the transformer...they are connected to fuses or breakers.
jwelectric
Senior Member
- Location
- North Carolina
250.4(B)(3) Bonding of Electrically Conductive Materials and Other Equipment. Electrically conductive materials that are likely to become energized shall be connected together and to the supply system grounded equipment in a manner that creates a low-impedance path for ground-fault current that is capable of carrying the maximum fault current likely to be imposed on it.
See 250.104 to find the requirements for complying with this section.
See 250.4(B) for the installation of the EGC. (1) Grounding Electrical Equipment. Non?current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth in a manner that will limit the voltage imposed by lightning or unintentional contact with higher-voltage lines and limit the voltage to ground on these materials
jwelectric
Senior Member
- Location
- North Carolina
Start at any receptacle and work backwards and tell me where you have to stop.
edited to add
Looking at these prints I can go from the receptacle all the way back to the secondary of the transformer supplying the building. The receptacle is connected to a wire that connects to a breaker that connects to a bus bar that connects to a breaker that connects to a feeder that connects to a breaker that connects to a bus bar that connects to a breaker that connects to a conductor that connects to a meter that connects to a conductors that connects to another conductor that connects to the secondary of the transformer giving conductivity between the secondary of the transformer to the receptacle.
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Truly, I do not know what this thread is about.
Grounded systems / circuits are referenced to earth. There is zero current flow to earth because of this, except for very rare and anomalous events.
Connected would imply a closed circuit and current flow with the earth, but the earth path is connected at a single point to the grounded (referenced to ground) system, so the earth is connected but the path through the earth is an "open circuit".
In order of strictness of NEC requirements:
Grounding electrode conductor: A wire from point A to point B with no splices or spliced using listed irreversible splices. Must be "accessible". Point A is the busbar where the system bonding jumper is located, point B is the "nearest" listed grounding electrode.
Equipment ground: A wire or raceway listed in 250.118, required to carry fault current and facilitate OCPD tripping. Also is connected to earth by convention, is bonded back to the source, which is bonded back to the GEC and the earth..
Bonding: Required to be able to carry fault current, but the path can be through the accessory metal structures, metal enclosures, strut, and other methods not listed in 250.118.
If the requirement says "ground it", the methods are stricter (250.118 materials). If the requirement says "bond it" the methods are looser, metal other than 250.118 methods may be used.
Grounded systems / circuits are referenced to earth. There is zero current flow to earth because of this, except for very rare and anomalous events.
Connected would imply a closed circuit and current flow with the earth, but the earth path is connected at a single point to the grounded (referenced to ground) system, so the earth is connected but the path through the earth is an "open circuit".
In order of strictness of NEC requirements:
Grounding electrode conductor: A wire from point A to point B with no splices or spliced using listed irreversible splices. Must be "accessible". Point A is the busbar where the system bonding jumper is located, point B is the "nearest" listed grounding electrode.
Equipment ground: A wire or raceway listed in 250.118, required to carry fault current and facilitate OCPD tripping. Also is connected to earth by convention, is bonded back to the source, which is bonded back to the GEC and the earth..
Bonding: Required to be able to carry fault current, but the path can be through the accessory metal structures, metal enclosures, strut, and other methods not listed in 250.118.
If the requirement says "ground it", the methods are stricter (250.118 materials). If the requirement says "bond it" the methods are looser, metal other than 250.118 methods may be used.
- Location
- Illinois
- Occupation
- retired electrician
It about changing the name of this conductor to reflect the fact that is is really a bonding conductor and not a grounding conductor.
jwelectric
Senior Member
- Location
- North Carolina
Even though the NEC does require that the EGC connect to earth as outline here See the underlined portion
250.4 General Requirements for Grounding and Bonding. The following general requirements identify what grounding and bonding of electrical systems are required to accomplish. The prescriptive methods contained in Article 250 shall be followed to comply with the performance requirements of this section.
(A) Grounded Systems.
(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.
Informational Note: An important consideration for limiting the imposed voltage is the routing of bonding and grounding electrode conductors so that they are not any longer than necessary to complete the connection without disturbing the permanent parts of the installation and so that unnecessary bends and loops are avoided.
(2) Grounding of Electrical Equipment. Normally non?current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth so as to limit the voltage to ground on these materials.
Thanks for the reply Don, but if you say "bond it", looking at 250.12, clean surfaces and paint removal required, or 250.8, sheet metal screw threads shall not be used, the wording seems to apply to grounding but not to bonding.
I could bond it using tin foil and paper clips as long as there was enough of it to carry the fault current. I am concerned about the applications where I will say "the grounding is not compliant" and the response will be "it is bonded".
- Location
- Illinois
- Occupation
- retired electrician
Nothing would change as far as the installation...all of the rules that tell us how to install and Equipment Grounding Conductor would be changed to match the new term of Equipment Bonding Conductor. The real point is that "grounding" is not the primary function of what we now call the Equipment Grounding Conductor.
Yep as I can see in this thread, grounding has a few folks confused. I have taught several grounding classes even wrote a book or two on the subject, and I make my living at it in the telecom sector. Trust me there are no bigger jerks than there is in the Telecom when it comes to grounding. Most of the equipment manufactures are clueless, especially the ones that claim they must have 5 ohms or less to earth impedance. What follows if 3 very simple circuit diagrams I have used that gets the basic idea across. Excuse the mess, but I drew it up real quick for here. Two circuits will work and safe, one will get you killed, and only one is compliant Can you tell which one and why they would or would not work?
I agree, even in a NEC compliant EGC is employed will not save your life. Even on a simple 120 VAC circuit, if there is a ground fault at the equipment, the chassis will have 60 volts until the fault is cleared. Now here is the shocker and killer. If that was say 480, you get hit with 240 or more volts during a fault.
@Mike
In the most technical sense of the word, if electrical energy can or does get carried by an entity, it is connected to the system... so using the broadest definition of connected, all conductors of a grounded system are grounded. In NEC usage the meaning varies with context.
Debate on...
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
Teach me, Mike: how does the earthing connection limit the voltage to ground on equipment, bearing in mind that the definition of "ground" in the NEC is given as, "The Earth."?
You are hanging your hat on that section, stating it is more important than the bonding principle. You are adamant on this point. All of us have seen countless examples that this section in the NEC is patently unenforceable and defies the laws of physics, yet you seem to believe it more important than sections the majority fully understand and believe to be far more important at the equipment served.
So please, without posting miles of code we already have access to, enlighten us. Why is it more appropriately called EGC instead of EBC.
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