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Old 06-16-2008, 07:44 AM   #1
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Grounding VS Bonding


Would it be correct that when discussing grounding vs bonding that the fault current must be routed back to the grounded source winding and all metal parts of the wiring system must be bonded back to ground so if any part becomes energized it will protect you from being the ground if the OCPD has not tripped. I know this is a very debated subject.
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Old 06-16-2008, 08:09 AM   #2
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;130741]Would it be correct that when discussing grounding vs bonding that the fault current must be routed back to the grounded source winding
huh?


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and all metal parts of the wiring system must be bonded back to ground
no

Quote:
so if any part becomes energized it will protect you from being the ground if the OCPD has not tripped.
partially

bonding is very simply put as: making 2 things electrically continuous. nothing more

grounding is another issue altogether.

you also need to understand the difference between a grounded system and a grounding system. The neut of a 120 volt system is a grounded conductor. The equipment grounding conductor (EGC) is a grounding conductor.

a grounded conductor is made to earth ground for the purpose of allowing a path for objectionable currents, accidental contact with high voltage, and to provide a 0 volt reference point.

electricity seeks to return to its source. That is why all electrical systems have at least two circuit wires. I'll speak to a 120 volt with a neutral since it is most common and easiest to explain.

a ground is not needed for this system to operate. It works just fine without a grounding conductor or actually even the grounded conductor being connected to earth ground.

the EGC is to allow a low impedance pathway for fault currents (unintentional short circuits) to be able to return to the neutral connection (the earth ground is not needed for this purpose) so enough current will flow through the overcurrent protective device (OCPD) to trip and stop current flow.

the reason all of this is connected to earth ground is in case of things like lightning strikes and unintentional contact with a high voltage source and this also allows a 0 reference point (neutral line to earth ground reads 0 volts. hot leg to neutral or earth ground (only because they are actually bonded together) will be 120 volts). If you removed the earth bond, you would still have 120 volts from the neutral to the hot leg but your voltage from ground would vary (a lot of factors will cause different readings).

so, thoroughly confused? I tend to write in disconnected thoughts so how I post may be hard to follow.

let me know what makes sense to you and what needs further explanation. Sometimes that is easier than rambling on fofr 2 pages.

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Old 06-16-2008, 05:54 PM   #3
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Grounding VS Bonding


NAP..are you an electrician?

some of that stuff I don't agree with (sorry not enough time to debate it all).

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Old 06-16-2008, 06:08 PM   #4
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Originally Posted by HandyPete View Post
NAP..are you an electrician?

some of that stuff I don't agree with (sorry not enough time to debate it all).

-pete
yes and I would be more than glad to discuss anything you don;t agree with. I have made mistakes in my life, proof of that is I am still working for a living so ask away.
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Old 06-16-2008, 07:43 PM   #5
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Hey Nap, no offense, judging by your post I thought so but, I just wanted to ask.

here goes...

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Originally Posted by nap View Post
the EGC is to allow a low impedance pathway for fault currents (unintentional short circuits) to be able to return to the neutral connection (the earth ground is not needed for this purpose) so enough current will flow through the overcurrent protective device (OCPD) to trip and stop current flow.
IMHO a "short circuit" is between two conductors thus, no EGC is in play. In fact, it serves no purpose for this.

you also gave a "NO" to all metal parts need to be grounded...

Hmmm? I like to see everything bonded to ground.

Utilities ground their systems. For human safety? nope, it's for detection and protection of the network. Once you ground a system, it's like you said...electricity will seek it's source. Because they do this, they need to spread the protection all the way to the end of the circuit. That said, what if the insulation of a conductor wears out and touches something metal? oupps...that metal becomes energized. Now, what if someone standing in water or bare earth touches the metal? dead.

So, in order to prevent accidental energizations, every metal part is bonded (groundED) to ground. Thus a low resistance path is created in order to increase the current (weird but true) so the damn breaker will trip!

insulation fails, metal gets energized, current flows, breaker trips..everyone's safe!

geez..I talk too much.

_ pete

BTW I was kinda talking to the laymen and not necessarily to you.
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Old 06-16-2008, 09:59 PM   #6
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Grounding VS Bonding


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Nap, no offense
No offense taken,


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IMHO a "short circuit" is between two conductors thus, no EGC is in play. In fact, it serves no purpose for this.
from wiki (because it is easy)
Quote:
A short circuit (sometimes abbreviated to short or s/c) allows a current to flow along a different path from the one intended
any unintended current flow is considered a short circuit whether it be to ground or another conductor. Therefore, EGC is critical, at least for the short to ground.

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you also gave a "NO" to all metal parts need to be grounded...
semantics. Take note, I said :

Quote:
the EGC is to allow a low impedance pathway for fault currents (unintentional short circuits) to be able to return to the neutral connection (the earth ground is not needed for this purpose) so enough current will flow through the overcurrent protective device (OCPD) to trip and stop current flow.
earth ground does nothing for a short circuit. The purpose of the EGC is to allow a path to the neutral of the electrical supply so the OCPD will trip. A system does not even need to be grounded for this to take place since it is basically an extreme overcurrent and the breaker trips on that action and the flow is from hot to neutral, not hot to ground.

all metal fixtures MUST be "grounded" per NEC but that is because that EGC is connected to the neutral of the service. The fact it is also attached to earth ground does it no benefit in this situation, well, let me change that, it does allow a 0 reference point since the neutral is also connected to earth ground and as such, a neutral will not read line voltage but if you understand this, you will understand why a dryer and an oven cannot have the EGC and grounded conductor in common anymore.



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Hmmm? I like to see everything bonded to ground.
so do I and it is a requirement in most situations but I was speaking in the theoretical sense. Attaching anything to ground does not provide and benefit for an overcurrent situation except for extreme situations where high voltage is introduced.

Quote:
Utilities ground their systems. For human safety? nope, it's for detection and protection of the network. Once you ground a system, it's like you said...electricity will seek it's source. Because they do this, they need to spread the protection all the way to the end of the circuit. That said, what if the insulation of a conductor wears out and touches something metal? oupps...that metal becomes energized. Now, what if someone standing in water or bare earth touches the metal? dead.
electricity will seek its csource regardless of being earth grounded. There are ungrounded systems all over the place. Ground is for protection of personel. I can run an electrical system just fine without an earth ground. (example: ungrounded delta services)

Quote:
So, in order to prevent accidental energizations, every metal part is bonded (groundED) to ground
It is connected to the EGC and that is connected to earth ground but the earth ground is not what provides the safety of the system. The EGC being connected to the neutral (grounded conductor) is what provides the safety.

Quote:
. Thus a low resistance path is created in order to increase the current (weird but true) so the damn breaker will trip!
right but earth ground has nothing to do with this.



Quote:
BTW I was kinda talking to the laymen and not necessarily to you.
don't BS me. You think I was wrong. The problem is when you start talking about this type of thing, you need to speak of EGC's and neutrals as a seperate issue than earth ground. An electrical system works just fine (including overcurrent protection) just fine without an earth ground. Example; an ungrounded delta service. It is intentionally NOT grounded but guess what, the breakers still work as intended. Why? because the current flow back to the source is what makes them trip, not current flow to ground.

actually, the earth is a fairly poor conductor and typically will not flow enough current to cause an OCPD to trip. Code requires no greater than 25 ohms for a single ground rod. At 120 volts, that would allow only 4.8 amps of current to flow. A 20, or even a 15 or 10 amp breaker would never trip but that much current would surely kill a man. So, how do you fix this? you make the current flow back to the neutral (via the egc) so the current flows fast and furious and the breaker trips.
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Old 06-17-2008, 05:53 AM   #7
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Grounding VS Bonding


Just my 2 cents, I agree with Nap, and had no problems understanding his first post, but you should have no problems understanding his 2nd.
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Old 06-17-2008, 06:25 AM   #8
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These were some very good posts. To make it clear to myself. I understand that the ground has nothing to do with fault current. I remember when there were no grounds. But what is still not clear, if all the metal components are bonded but not to ground what is the point of bonding. If everything is bonded but not grounded and becomes energized you are the ground if the OCPD has not opened. Remember the ranges that if the neutral opened or was missing it would shock you.
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Old 06-17-2008, 06:30 AM   #9
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Sorry I forgot my point. Old age. If you by a pool pump and it comes with a three prong plug on the frame it has a lug and instructions that it must be grounded. What is the point since it comes grounded or if it is hardwired with ground is it still required to ground the frame or is this bonding?
Sorry
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Old 06-17-2008, 08:10 AM   #10
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What is the point since it comes grounded or if it is hardwired with ground is it still required to ground the frame or is this bonding?
The plug ties it to an equipment ground. The lug on the side of the motor is for attaching the bonding wire to the bonding grid, per the code's bonding requirements for swimming pool equipment.
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Old 06-17-2008, 02:31 PM   #11
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. But what is still not clear, if all the metal components are bonded but not to ground what is the point of bonding. If everything is bonded but not grounded and becomes energized you are the ground if the OCPD has not opened. .
try this. think of grounded conductor, grounding conductor, and earth ground for a minute in your head

grounded conductor= neutral=white or gray wire=center tap of the supply transformer happens to be connected to earth ground also

grounding conductor= green wire=bonded to neutral service disconnect and also happens to be connected to earth ground

earth ground=that stick in ground

all current seeks to return from which it came. on a 120 volt with neutral, that would be where the neutral comes in. Now, as you said, we do not, any longer, intentionally bond the grounded and grounding conductors at the appliance anymore for the reason you stated.

Now, since we do not bond those together at the appliance, we still need a fault current path for when the frame becomes energized. That is the grounding conductor.

OCPD has nothing to do with earth ground. All it needs is excessive current flow which either the neutral will allow, or in the case of energizing an unintended chunk of metal (frame of the dryer for example), the grounding conductor provides the path.

this will allow the current to flow whether anything is earth grounded or not. We really don;t care about earth ground for this purpose because remember, current will return to from whence it came namely, the transformer. Earth ground has nothing to do with it

So, where does earth ground come in? Well, it serves several purposes which the code actually states as: 250.4 (A)(1) Electrical System Grounding:

Electrical systems that are grounded shall be conenected to the earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilze voltage to earth during normal operation.

what that means is: if a higher voltage than the system is designed for is imposed on the system, the ground will provide a pathway for that voltage to drain off. This includes lightning, system surges, or other voltage sources that may accidentally be imposed on the system. The last part means this provides a reference voltage that remains constant. That is why you can read 120 volts to ground (earth ground actually). If you removed the earth ground, you would still have 120 volts line to neut or line to the grounding conductor (because it is still connected to the neut) but you would have a floating voltage to earth ground. This connection remedies that. If you have ever worked on control systems with a control transformer that does not have a grounded leg, you will understand what that earth ground connection does for the reference voltage.
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Old 06-21-2008, 03:57 PM   #12
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Hi Stubbie.

Are you doing what I am doing? Are you amused by the incorrect advice by the "closet" electricians? I'm totally amused. If they keep up their "good" work, they may get someone killed.

There must be a million electrical threads on the internet. ALL of them attract unqualified people. On the odd occasion, the qualified people are WRONG!!!!! The only way to secure a correct answer is to question the answerer. A "qualified" person should be able to mathematically, physically & chemically give a correct explanation. This explanation can usually be easily checked.

Bonding & Earthing are two different things with two different purposes. This situation exists for most other countries besides America.

"Equipotential bonding" exists for a reason that has nothing to do with immediate "personal" protection. "Earthing" (grounding) is directly connected with "personal" protection. I think that you will find that the Main Neutral conductor is connected to the Main Earth conductor AT THE SWITCHBOARD ("breakerbox" for you yanks or pommies) for the reason of impedance. Quite simply, you now rely on an earth/neutral "return" system. There are 2 current paths back to the supply transformer. These paths are intended to reduce the "impedance" back to the supply source & as such, allow OCPD's to trip quicker than if one return path existed.

By "equipotentially" bonding equipment to the earthing circuit, the chance of extraneous voltages on metallic cased equipment is reduced. Even though this is NOT intended to be a part of the "personal protection" earthing circuit, it does assist in the reduction of possible "personal" earth faults.

Equipotentential Bonding DOES NOT provide "personal" protection when it comes to earthing.
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Old 06-21-2008, 04:49 PM   #13
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A "qualified" person should be able to mathematically, physically & chemically give a correct explanation. This explanation can usually be easily checked.
Wrong a qualified person is one that has the knowledge and can teach others. You failed there.
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Old 06-21-2008, 04:54 PM   #14
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A "qualified" person should be able to mathematically, physically & chemically give a correct explanation. This explanation can usually be easily checked.
Wrong a qualified person is one that has the knowledge and can teach others. You failed there.
Please explain.
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Old 06-21-2008, 05:16 PM   #15
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You seem to want to use fancy words that most DIY people would not understand. Only people in the trades could follow. If you put it in layman terms we could maybe better understand.
Its like asking a doctor why your knee hurts and he tells you in terms only doctors would understand. If he put it in layman terms you might know why your knee hurts. See the difference.
I use this as an example and not to imply that electricians are on the same intellectual level as doctors. We are DYI people looking for help understanding and we do thank everyone of you for trying to help and educate. Even doctors make mistakes, ask the lawyers.

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