What Is Electrical Grounding?

[don_resqcapt19]

It is my understanding that the term equipment grounding conductor was replaced with the term equipment bonding conductor.

I submitted proposals for the 2005 code cycle to do that in the NEC. A majority of CMP 5 voted in favor, but not a 2/3s majority as required to accept a proposal

 

[__dan]

My preference would be three words, bonding, equipment grounding, and earth grounding.

Bonding is using methods other than those listed in 250.118 for interconnection. There is a lot of field activity done by people other than electricians, welding frames, assembling steel shelving, equipment or plant fabrication. Bonding is a lower standard of performance compared to grounding and does not imply it will trip a breaker or is connected to earth. Two pieces are joined together electrically with a general performance standard (effective path?) using conventional and varied field methods, metal to metal contact occurring naturally in the course of construction.

Equipment grounding is a strictly specified and required system that will trip a breaker using code required materials and methods. Under the existing code, the EGC is eventually bonded back to the GEC and the earth.

Earth grounding is strictly specified as a connection to the earth with strict compliance requirements regarding materials and methods.

Obviously among electricians and wiring there is a lot of non compliance with the code requirements as they are now.

There are also a lot of manufacturer requirements for earth grounding, for IT equipment, where imo, the manufacturer is using the correct wording. The equipment ground is already required by code. The manufacturer is adding a requirement for an earth ground by adding it to their instructions. They are not substituting the earth ground, they are imo requiring a second dedicated conductor for a different purpose using a different circuit path. It's an adder.

 

[don_resqcapt19]

...
Bonding is using methods other than those listed in 250.118 for interconnection. There is a lot of field activity done by people other than electricians, welding frames, assembling steel shelving, equipment or plant fabrication. Bonding is a lower standard of performance compared to grounding and does not imply it will trip a breaker or is connected to earth. Two pieces are joined together electrically with a general performance standard (effective path?) using conventional and varied field methods, metal to metal contact occurring naturally in the course of construction.
...

The true function of what we call the EGC is really a bonding function. It is to bond the non-current carrying parts back to the system grounded conductor. The connection to earth has nothing to do with its fault clearing job. As long as we use the term EGC we will continue have many who think that the connection to earth is what clears the fault and makes the system safe.

 

[__dan]

The true function of what we call the EGC is really a bonding function. It is to bond the non-current carrying parts back to the system grounded conductor. The connection to earth has nothing to do with its fault clearing job. As long as we use the term EGC we will continue have many who think that the connection to earth is what clears the fault and makes the system safe.

Agree and disagree. Fault clearing, that's a test question 99% of the population will fumble through haphazardly. Some will get the question right only because statistically, not everyone can get the question wrong. This is where the code rules, manufacturer requirements, need to be taught and enforced.

But the population's perception of safety, they are standing on bare ground in bare feet and they think, "I can touch that metal appliance surface safely because it is grounded".

To me, the word bonding does not carry the same weight as the word grounding. Bonded is a word used many times elsewhere with different meanings. The surfaces could be plastic glued or heat welded together. I don't see the upside, the increased clarity and reduced confusion from the proposed change. Grounded is already in common use and widely held in the population's mind, even if misunderstood and used incorrectly. That's what the electrician is for. The population does not say "I grounded it", they say "my electrician grounded it".

I will say that in all cases the EGC is grounded by being bonded back to the GEC and grounding electrode. To say the EGC is grounded is not an incorrect usage.

Not arguing for the sake of arguing. Just saying, at a technical level the word usage has a precisely defined meaning and purpose, to convey information or understanding, and sometimes a legal definition and obligation to comply. There is a duty to perform, to all use the wording the same way as defined.

 

[don_resqcapt19]

...
I will say that in all cases the EGC is grounded by being bonded back to the GEC and grounding electrode. To say the EGC is grounded is not an incorrect usage.
...

That is correct, but neither of those things have anything to do with clearing the fault and making the system safe. The use of the word "grounding" in the term is the source of confusion leading far to many to think that all you have to do is make a connection to earth to make it safe.

 

[GoldDigger]

One thing that comes to my mind at this point is that "likely to become energized" metal can only be bonded, even indirectly, to a current carrying conductor for fault clearing purposes if that conductor is in fact grounded.
To that extent, the word grounded is inseparably linked to fault clearing.

Tapatalk!

 

[jxofaltrds]

One thing that comes to my mind at this point is that "likely to become energized" metal can only be bonded, even indirectly, to a current carrying conductor for fault clearing purposes if that conductor is in fact grounded.
To that extent, the word grounded is inseparably linked to fault clearing.

Tapatalk!

I can have no 'earth ground' and the breaker will still trip. (if everything else is wired correctly)

 

[dereckbc]

I will say that in all cases the EGC is grounded by being bonded back to the GEC and grounding electrode. To say the EGC is grounded is not an incorrect usage.

But a Earth connection has noting to do with clearing a fault. In fact you can say a grounded system is dangerous and prone to frequent outages. That is the exact reason why industry does not use grounded systems. No car, boat or plane uses earth, but they are safe as they use the frame to supply a return fault path, or if it is mission critical they are not bonded at all and install OCPd on each polarity or phase and use GFD in the event one phase or polarity should become faulted so maintenance crews can schedule a timely shutdown to repair the fault. In the meantime the equipment works just fine until the fault can be isolated and repaired. .

 

[__dan]

That is correct, but neither of those things have anything to do with clearing the fault and making the system safe. The use of the word "grounding" in the term is the source of confusion leading far to many to think that all you have to do is make a connection to earth to make it safe.

But a Earth connection has noting to do with clearing a fault. In fact you can say a grounded system is dangerous and prone to frequent outages.

Too funny. The change has not yet been made and you're already accusing me of being politically incorrect.

I have never seen a ground rod substituted for an equipment ground and the system called grounded. I have been told IBM has this spec for a piece of hardware, isolation from the equipment ground with a separate extensive isolated earth ground, which I disputed, requiring a single point grounding connection from the new to the old system. You are citing a problem that I have never seen to exist with professionally wired equipment (don't cite the neighbor's self wired chicken coop).

Adding an independent ground rod at equipment is a common manufacturer requirement (for network or CNC machines). This is widely ignored and it is never specified as a substitute for the equipment ground. It is always assumed and required that the mandatory equipment ground also be present. The ground rod is specified as an adder, not as a substitute.

I have never seen the requirement to substitute the ground rod and also not have an equipment ground. This is the problem you are citing that is happening. Cite your specific occurrence where you have seen this, a ground rod substituted for the equipment ground and the equipment ground also omitted. You are citing this as a problem that is happening.

Lastly, for the problem you cite, do not change the name to bonding which has a vague understanding with multiple preexisting meanings. Change the name to "the fault clearing path".

 

[dereckbc]

Too funny. The change has not yet been made and you're already accusing me of being politically incorrect.

I beg your pardon; but what did Don or I accuse you of?

 

[__dan]

I beg your pardon; but what did Don or I accuse you of?

But a Earth connection has noting to do with clearing a fault. In fact you can say a grounded system is dangerous and prone to frequent outages.

Recommending an unsafe wiring method, you're saying grounding is unsafe and bonding is required.

 

[don_resqcapt19]

Recommending an unsafe wiring method, you're saying grounding is unsafe and bonding is required.

Not even close to what I have been saying. I am saying that the very use of the term "equipment grounding conductor" results in an unsafe path.
As far as bonding not being defined it is defined in many case in the code. What about the "main bonding jumper" and the "system bonding jumper"? These two bonding connections connect what is now called the equipment grounding conductor to the system grounded conductor...without those bonding connections there is no fault clearing path.

While, it is clear that you understand the term EGC, many installers do not and because of the word "grounding" in that term they continue to think that the connection to the earth is the most important part of the EGC. That is just not the case, the connection to the earth does not clear faults, and the connection to earth does not prevent dangerous voltages on the conductive non-current carrying parts of the electrical system.

 

[dereckbc]

Recommending an unsafe wiring method, you're saying grounding is unsafe and bonding is required.

Please explain to me how that accuses you of anything?

As for my statement is 100% accurate. Grounded systems are dangerous and prone to unnecessary outages. I never once implied or said anyone should not comply with electrical codes, just simply stating facts.

Great example if you come into contact with say 120 Single Phase service and are touching a chassis or in contact with earth, you will be electrocuted. No OCPD Device will operate unless it is on a GFCI circuit. Remove the earth reference and chassis bond, and no problem coming into contact with either phase, no shock. This whole thread is about is earth involved in clearing electrical faults in Low Voltage systems under 600 volts. The answer to that question is NO, earth has nothing to do with it.

Take a hot line to ground, sparks fly, wiring burns, you have an outage, and hopefully an OCPD will operate before damage becomes severe. On a non grounded system a phase can go to ground or chassis, nothing happens other than the required GFD alarm device signals a fault so a timely shut down can be scheduled at a later time to locate and repair the fault. Otherwise the machines keep on working with no damage.

The only reason we have earth or chassis referenced system has to do more with simplicity and economics of over current protection device rather than life safety. If life safety were the driving factor, electrical systems would not be referenced. Do not confuse a grounded system with grounded chassis and equipment as those are two separate issues. Even in ungrounded systems you still need and are required to earth (or bond to something in place of earth like a vehicle frames) the chassis, raceways, equipment frames etc, or about anything that can conduct electricity.

 

[charlie b]

Dereck, I agree that touching a "hot conductor" in a grounded 120 volt system, while also being in contact with planet Earth, will likely result in electrocution. But I submit that touching a "hot conductor" in an ungrounded 120 volt system, while also being in contact with planet Earth, is also likely result in electrocution. I am not certain if that agrees or disagrees with your statements within this thread, for I haven't been following the entire discussion. In the second scenario, the thing that completes the circuit, and that could thereby result in electrocution, is the capacitive reactance that exists between the conductors of the electrical system and planet Earth.

 

[dereckbc]

Dereck, I agree that touching a "hot conductor" in a grounded 120 volt system, while also being in contact with planet Earth, will likely result in electrocution. But I submit that touching a "hot conductor" in an ungrounded 120 volt system, while also being in contact with planet Earth, is also likely result in electrocution. I am not certain if that agrees or disagrees with your statements within this thread, for I haven't been following the entire discussion. In the second scenario, the thing that completes the circuit, and that could thereby result in electrocution, is the capacitive reactance that exists between the conductors of the electrical system and planet Earth.

I am aware of capacities coupling to earth. However in a residential system is so minimal (pico farads) it can be ignored. You are correct it can be of great concern in a commercial or industrial application where the system is far larger in size and ran in conductive raceways as the capacitance can easily reach the milli-farads and thus can conduct lethal current at 60 Hz.

The point I am trying to make is grounded systems are more dangerous than there ungrounded systems, not to mention much more prone to outages. The driving factor IMHO is grounded systems is driven by economics of OCPD and simplicity. Utility distribution is not grounded until the last leg of distribution, and for industrial is not grounded. Again that has more to do with economics and little to do with safety.

So to make myself crystal clear I do not advocate for anyone to not ground a system or follow electrical codes. I am only trying to point out that a earthed system does not make it safe or has anything to do with clearing faults on low voltage systems 600 volts and less. I am just trying to make pros think and clear up myths.

The primary reason for grounding a system on a single phase 240/120 residential system (3-phase is another issue) is to provide a fault path for unintentional contact between primary and secondary distribution and a planned path for lightning faults. Secondary purposes are:

Economic OCPD
Short out coupling capacitance to ground. Which makes it more dangerous to accidental contact and prone to outage.
Static discharge.

It has no other purpose. than the 5 reasons listed.

FWIW and Fun; If I were the Electricity CZAR I would make all residential systems balance 240/120 where L to L is 240, and L-G is 120. It would eliminate a lot of problems of an unbalanced system and still easy and economical to provide OCPD. It would require both phases (dual pole breakers) to have OCPD.

 

[__dan]

Please explain to me how that accuses you of anything?

As for my statement is 100% accurate. Grounded systems are dangerous and prone to unnecessary outages. I never once implied or said anyone should not comply with electrical codes, just simply stating facts.

Great example if you come into contact with say 120 Single Phase service and are touching a chassis or in contact with earth, you will be electrocuted. No OCPD Device will operate unless it is on a GFCI circuit. Remove the earth reference and chassis bond, and no problem coming into contact with either phase, no shock. This whole thread is about is earth involved in clearing electrical faults in Low Voltage systems under 600 volts. The answer to that question is NO, earth has nothing to do with it.

Take a hot line to ground, sparks fly, wiring burns, you have an outage, and hopefully an OCPD will operate before damage becomes severe. On a non grounded system a phase can go to ground or chassis, nothing happens other than the required GFD alarm device signals a fault so a timely shut down can be scheduled at a later time to locate and repair the fault. Otherwise the machines keep on working with no damage.

The only reason we have earth or chassis referenced system has to do more with simplicity and economics of over current protection device rather than life safety. If life safety were the driving factor, electrical systems would not be referenced. Do not confuse a grounded system with grounded chassis and equipment as those are two separate issues. Even in ungrounded systems you still need and are required to earth (or bond to something in place of earth like a vehicle frames) the chassis, raceways, equipment frames etc, or about anything that can conduct electricity.

I have to say I am now completely confused about what you are saying or trying to say.

Ungrounding every circuit and adding GFI is a total non starter except for the GFI manufacturer. Residential GFI's have a useful life less than five years. They go bad frequently and fail to trip on the red button but the power is still on (they do not self test or alarm for protective function failure).

Ungrounding, removing the earth reference from the frame, can never be accomplished in practice. There will always be haphazard and unintentional earth contact with the exposed metal of the load or its attached systems. You are describing something you can only build in a lab that works only during the test period. You would be proposing that every piece of metal nationwide that is part of the load would be double insulated, insulated from both earth contact and human contact.

You cited plane, train, boat, and car wiring which are not under the jurisdiction of the NEC. Also there's a difference going from <1kW loads in a car to >1 MW loads in a facility, specifically, voltage drop and the potential for parallel paths with the neutral, "grounded" conductor. In a car, train, or boat you can eliminate parallel paths by using the chassis (and DC), which cannot be done in a plant (AC power, EMI and RFI radiation). If you want to propose a Direct Current facility power distribution system, I would agree you could probably reliably use the steel frame of the building for an intended current path.

You cited reliability for critical loads. Existing methodology is layered dual feed and dual power cords at the device with the device dual power supplies paralleled redundantly at the output. There are dual feeders with a fast transfer static switch at the PDU, then dual power cords from two independent PDU's to the device (which I'm sure you know). Implemented correctly as intended, this allows any part of the power distribution system to be shut off for servicing. I did not understand what you proposed as an alternative.

Grounded electrical systems less than 1 MW are extremely reliable, especially compared to alternatives (batteries, generators, solar). Over 1 MW resistance grounding with GF detection may be advised or preferred.

I would say the highest percentage of problems is not due to the currents codes but failure to follow, comply with, or maintain to, the existing codes.

250.4 ( A ) 1 through 5 is pretty clear. This thread is claiming 250.4 is improperly worded. The problem is not with the naming convention, it would be with the lazy clueless fakers ignoring what the code says. Changing the name will not make the lazy suddenly get up and go, the clueless suddenly become competent.

 

[dereckbc]

250.4 ( A ) 1 through 5 is pretty clear. This thread is claiming 250.4 is improperly worded. The problem is not with the naming convention, it would be with the lazy clueless fakers ignoring what the code says. Changing the name will not make the lazy suddenly get up and go, the clueless suddenly become competent.

Then I dare to say you do not understand what 250.4 (A) is telling you. Read 250.4 (B) and compare the two

What I suspect is you do not understand what the terms GROUNDED SYSTEM, UNGROUNDED SYSTEM and GROUNDED actually means. Ground does not imply earth empirically. It can be anything including the frame of your work truck aircraft, boat, ship, or flashlight.

Answer these two questions.

1. Let's say you set a 120 volt battery on the ground with no wiring of any kind and you touch either polarity. What happens to you?.


2. A bird lands and perches on a 1 MV overhead line. What happens to the bird?

The only right answer is NOTHING.

There is no complete circuit to conduct current.

Now take the 120 volt battery example from above, bond one of the two battery post, makes no difference which one, to a ground rod driven into the dirt. Wet the area down, take off your shoes and dig your toes into the mud and pee on the ungrounded battery post terminal. I bet you will not do it again. I learned that lesson on the farm with an electric cow fence at the age of 6 50 years ago. :ashamed1:

 

[__dan]

The bird is safe because the air is an insulating material. The bird is contained within the insulator also serving the wire. Yes you could take the same approach with humans, contain them within insulators. Require everyone to wear the skin tight rubber suit to contact electrically operated devices. I know many would like to pass that law.

I will take a closer look at 250.4 A and B. At first guess they may be identical except for using the earth as reference.

BTW, induced voltages through the air from nearby lightning strikes are no joke and cause a lot of personal injury and property damage. That would be damage inside the building, brought in from outside aerial exposed wires. Try running your TV set with an ungrounded aerial antenna and see how long the tuner lasts.

Same with the battery scenario. Run 100 ft aerial to the solar panels, another 100 ft aerial to the other outbuilding, and pray the charger, inverter, can withstand the transient overvoltage from nearby lightning strikes.

I agree the earth connection does nothing ... most of the time. During the time it does nothing, it provides a clean reference point for instrumentation and sensitive electronic technology. During the time it does something, limiting induced transient overvoltage from the sky and elsewhere, it is protecting life and property, mitigating damage.

Key point is that when necessary, the intended wired connection to the earth can safely pass much more current than the haphazard and accidentally occurring connection to the earth.

 

[jxofaltrds]

The bird is safe because the air is an insulating material.

This is where I stopped reading.

PS I think Tesla thought that too.

 

[__dan]

This is where I stopped reading.

PS I think Tesla thought that too.

I was already getting the feeling, how did I get sucked into this thread.

The air is an insulator under the conditions provided. The bird picks up the same highly energized free electrons from the wire by contact. The charge is static except for the 60 Hz fundamental. There is no place for the highly mobile free electrons to go from the bird except back into the wire because the voltage is lower than the breakdown voltage rating of the air (neglecting air moisture).

There are ways to electrocute the bird using Tesla technology and ways to transmit power using the bird and Tesla tech.

The typical Tesla coil uses very high frequency, high voltage. The high frequency travels on the surface of the person or bird, not through the interior where burn damage would occur. You can see this in demos of Tesla coils where the user touches the coil and extends his hand. Lightning, corona shoots from his hand. The current path is over the body surface (skin effect) and they use metal thimbles or metal gloves at the fingertips to prevent burns.

So you could tie the bird to the top of a Tesla coil with some metal points attached to the extremities. That will give you some current flow into the air with the path being over the body surface, not through it.

Grounding the energized bird would of course have a less desirable effect (the air is acting as a current limiter).