Why ground [earth]

[suemarkp]

Thank you for post #19. I can't believe some of the things posted in this thread...

The reason you ground is because the utility has chosen to earth itself and the neutral of your transformer. That has created a return path in the earth that can kill you, but not trip a breaker at voltages below 600V.

I think lightning is the main reason the utility grounds things. Whether they should ground the secondary of your transformer would be an interesting study.

There are some things that the physics people have correct, and that is how charges can build up on rotating machinery (generators, helicopters, etc). A high impedance ground would be sufficient to bleed off those charges.

 

[tryinghard]

...BUT should something short in the circuit(neutral to hot) it would raise havoc with the supplying transformer and the utility company would not be happy.

This would be an extremely high current situation and if low resistance it would cause an instantaneous trip. Creating an effective ground fault current path has nothing to do with the utility companies disposition and everything to do with safety.

Adding the EARTH ground gives a very low resistance path for any stray current or voltages to follow in some kind of breakdown.

So with your assertion when will the short clear? All current has a source; stray current is seeking its source not earth. Correct wiring practices and bonding will eliminate/disable stray current problems not electrode connections to earth.

Your assertion above is not true! The earth is always an unknown resistance and usually high. NEC does not allow its use for fault current see 250-4(A)(5). Ohms law proves the earth will allow fault current to remain on conductive items without opening the circuits: With premises wiring of 600 volts and less, unlike high voltage, 600 volts or less grounding to earth IS NOT effective to open a circuit that has ground fault, in fact it usually allows circuitry to remain activated.
A- 4.4A=110V/25 ohms
B- 11A=277/25 ohms
C- 19A=480/25 ohms
As you can see these circuits will NOT open even with 15 & 20A protection, respectively!

The actual bonding of EARTH ground to the neutral of a service serves as a SAFETY . It equalizes the neutral with the "ground" (EARTH).

Yes bonding is extremely important not because it allows a path to earth but because it allows a path from non-current carrying items to the power supply source usually the XO of a transformer. The bonding of the neutral at the service disconnect completes the effective ground-fault path as described in 250-4(A)(5) enabling ground fault protection, without it ground fault protection is disabled and dangerous touch voltage will remain where it does not belong.
How is the serving neutral equalized to earth and why would we want this? It cannot be equal at 10', 30', 80', 150'...in other words this is not obtainable. But why would we want this anyway because the only purposes for ground as per NEC is: "to limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines…as per 250-4(A)(1)"

...there is a vast world of answers to why we do or do not use a GROUND , or more precisely an EQUIPMENT GROUND. Many electronic circuits refer to "ground" but are in all actuality, referring to a DC return path, ie, one that is lower in voltage than the supply path.

It helps to remember if it is current carrying it's not a frame!
Part VI of 250 does a great job of qualifying equipment grounding I just wish it would refer to its intended use as bonding instead of grounding. It uses grounding because its ultimate path connects to a circuit conductor that happens to be connected to ground but I also think this conductor should be referred to as return conductor. Either way it helps to read 250-4(A)(4)&(5) before part VI of 250 to align with it true purpose, the creation of a permanent, low-impedance path that can carry the maximum ground fault current likely to be imposed on it from any point on the system to the electrical supply source.

Grounding is confusing if not understood exactly what the term means.

I agree to its misuse but it really does simply mean connection to "The Earth", it has noting to do with circuitry function

Sorry to pounce you MrHandy2005 but I've recognized the misuse of terminology is actually causing misapplications and dangerous installations; this is what I'm really fighting.

 

[MrHandy2005]

I am now confused....

I am now confused....

If we must bond the neutral with EARTH ground at the service entrance , and the EARTH does not serve as any protecttion to the feeding transformer, why must we do it then? Why can't the utility co just EARTH ground the neutral at the transformer feeder?
One of the biggest errors that I see is electricians(or those who think they are) BELIEVING that Neutral and EARTH GROUND are the same thing. The neutral is only a common point between two or more windings of a transformer. Without having that little bit of information, they are putting themselves and others in great danger. I have seen and corrected , in industrial settings, many , many services without any EARTH ground. Sure they will work just fine but only until there is a lightning strike or otther surge that the serving transformer simply cannot dissipate.
Earth grounding is SAFETY. As with many other installations I have done in commercial settings. I ground anything metal that could possibly come into contact with anything hot in the service. A steel building is grounded directly back to the service EARTH ground. I do run EGC in conduit. I do not trust emt connects to provide a good path....over time they loosen up, become corroded , etc. Bottom line, any work that I do is as safe as I can possibly make it. Sometimes at a greater expense but which costs more,,,,lives or wire?

 

[MrHandy2005]

"So with your assertion when will the short clear? All current has a source; stray current is seeking its source not earth. Correct wiring practices and bonding will eliminate/disable stray current problems not electrode connections to earth."

There is the word again "bonding"......I ask simply....bonding what to what?

 

[76nemo]

If we must bond the neutral with EARTH ground at the service entrance , and the EARTH does not serve as any protecttion to the feeding transformer, why must we do it then? Why can't the utility co just EARTH ground the neutral at the transformer feeder?
One of the biggest errors that I see is electricians(or those who think they are) BELIEVING that Neutral and EARTH GROUND are the same thing. The neutral is only a common point between two or more windings of a transformer. Without having that little bit of information, they are putting themselves and others in great danger. I have seen and corrected , in industrial settings, many , many services without any EARTH ground. Sure they will work just fine but only until there is a lightning strike or otther surge that the serving transformer simply cannot dissipate.
Earth grounding is SAFETY. As with many other installations I have done in commercial settings. I ground anything metal that could possibly come into contact with anything hot in the service. A steel building is grounded directly back to the service EARTH ground. I do run EGC in conduit. I do not trust emt connects to provide a good path....over time they loosen up, become corroded , etc. Bottom line, any work that I do is as safe as I can possibly make it. Sometimes at a greater expense but which costs more,,,,lives or wire?

I wouldn't work with you if you didn't pull an EGC.

 

[iwire]

There is the word again "bonding"......I ask simply....bonding what to what?

Bonding non-current carrying parts back to the source of the current which in most cases is the utility transformer......not bonding to dirt.....that does very little.

 

[andinator]

I wouldn't work with you if you didn't pull an EGC.

Why? Conduit is listed as an EGC.

 

[boboelectric]

Thank you for post #19. I can't believe some of the things posted in this thread...

The reason you ground is because the utility has chosen to earth itself and the neutral of your transformer. That has created a return path in the earth that can kill you, but not trip a breaker at voltages below 600V.

I think lightning is the main reason the utility grounds things. Whether they should ground the secondary of your transformer would be an interesting study.

There are some things that the physics people have correct, and that is how charges can build up on rotating machinery (generators, helicopters, etc). A high impedance ground would be sufficient to bleed off those charges.

My conclusions also

 

[76nemo]

Why? Conduit is listed as an EGC.

If you truly hold that concept, we are from different planets. How in the HELL the NEC considers conduit, rigid or not, as a fault path is beyond me. If you don't pull a segregated EGC, let me know ahead of the contract. That is about as lazy, penny-pinching, foolish, underminded, "what were you thinking?" bologna as it gets.

I see you not pull one, and I'll never refer you again.

It is how it is.

 

[crossman]

I see you not pull one, and I'll never refer you again.

Good thing that your referral isn't needed. If it was, 95% of commercial electricians would be "not referred".

 

[76nemo]

Guess that's 95% of the work party who doesn't stand in my league. It's O.K. to be different though. We're all entitled to our own opinions:wink:

 

[tom baker]

If you truly hold that concept, we are from different planets. How in the HELL the NEC considers conduit, rigid or not, as a fault path is beyond me. If you don't pull a segregated EGC, let me know ahead of the contract. That is about as lazy, penny-pinching, foolish, underminded, "what were you thinking?" bologna as it gets.

The code is a minimum standard. Feel free to make a code proposal to change 250.118.
We often go beyond the code minimums, for example for dwelling units we use three way switches and install the light switches next to the door, neither of which (OK stairs) are required.

 

[cadpoint]

Let me apologize to the original poster, tryinhard, this is a direct answer to being highlighted Quote for Quote, I've done my best to put some effort into answering Crossman #19 post, in no way am I trying to steal this thought provoking post.

Let me throw my thoughts in here solely so I can be corrected if I am wrong. I am not being rude, just trying to learn.

Let me start with the last statement first then I'll go in order.

Someone above noted that electronic circuits often use the term "ground" as one side, or perhaps the center point of DC sources. This is a totally different usage of the term than what we as electricians are doing. This has definitely messed things up with our thinking.

|The use of the term ground (or earth) is so common in electrical and electronics
|applications that circuits in vehicles such as ships, aircraft, and spacecraft may be spoken
|of having a "ground" connection without any real connection to the Earth.
http://en.wikipedia.org/wiki/Ground_(electricity) (( I personally don't like using Wiki- but so be it))
The above is a quote from ?Ground (electricity) third paragraph.

#1. When you get a different name for that leg of service that completes the service let me know.
#2.If you don't know and understand the difference between the 3- G's then yes in-fact one don't belong in our field.

The word neutral doesn't appear in NEC 05' in the Article 100 nor is it in the Index.

Article 100 - Ground. The earth NFPA 08'.

I quoted the NEC, there not much humor in this crowd, or I don't get to express my humor, I've had Ten posts ripped out over the last month, how about U ?
If your going to stop me from Posting then take it out of MY Profile to, there no sense in me seeing a post vaporize in the wind and still have it show up my Listed subscriptions!

Based on the above quoted definition of ground, the following statement is not correct, it is misleading, and an old wife?s tale that has confused many electricians and muddied the waters of grounding and bonding for the last 100 years.

See #2 above (frankly I think that the general line of the thread is using three different variables of the same word for three different applications)

Because the basic circuit(s) of AC or DC needs a ground for some form of work to be done , IE it completes the circuit.

#3 IE it completes the circuit. Let me say it is a complete circuit. Seems that certain people read right past that part so I slanted it and underlined it. Refer to #1 above.

A flashlight does not require a connection to the earth to work. Electrical circuits on a spacecraft which is halfway to Mars do not require a ground to work. The service on your house does not require a connection to earth to work.
Electrical work can be done without any relation or connection to earth.

Refer to #1 above & #3 IE it completes the circuit
Now the first sentence yes in fact that truth. The second sentence if it is a complete service. the Third, I really have a problem with electrically describing, but by using the Ground wire on the pole or on the Service Side, see post #21.

Now granted you can run both a truly resistive load and 2-pole or 3 phase, with out a neutral (grounded), but I can only think of a purely resistive load. Now again, you are correct, I?ve seen it in manufacturing plants.
Frankly I didn?t learn my vocation that way, and have learned ?here? that under certain conditions a fault will not be cleared.

For current to flow, all you need is a potential difference and a path which allows current to flow. This could be a solar cell with a wire to a load and another wire back to the opposite side of the solar cell.
I can build a generator which will power a lamp and completely isolate the entire thing from earth. A path through earth is not necessary for a circuit to work.

Here
Are You really Sure ? no ground, no grounded, no grounding, no bonding,
OK as Said, I?ve seen 3 Pole and a Ground wire (to clarify no neutral)
Hey teach me something! You can?t just install it that way any more. Maybe if its sealed by an engineer but the one I was with, was as shocked as I to see what we both were looking when we looked at an existing service just as you described, and we just left it as is!
The correct way we are required to wire a generator something is going to touch that service. Maybe you can wire it that way, But I wouldn't want to touch it!

The earth's core is a bigger electron draw that we use to help complete a circuit.

Incorrect. This is one of the most misunderstood thoughts out there.
Electrons from a voltage source will leave the negative terminal and migrate in a completed path to the positive terminal. There is no need for the earth to play any role in this.

Here
You know it funny that Physic's is back in the conversation, Let me say this, the same equation that measures atomic repulsion and attraction of atom's is the near same equation that they put those satellites in space with.
F=m1m2/d2 is Newton?s law on Gravity
F=k*Q1*Q2/d2 is Coulomb?s law

In the units of the Syst?me International, universally used in science, there are no conversion factors for the base units, so we can relate the newton, the unit of force, to other base units: 1 N = 1 kg.m.s-2.

http://www.glenbrook.k12.il.us/gbssci/phys/Class/estatics/u8l3b.html

Coulomb?s work is based on a ?Newton? with is a measurable quantity!

The electrons coming out of a generator do not want to go into the earth.
They want to travel toward the opposite side of the power source.

I don?t quite get that last part of the statement, But I?ll let that go: ?They want to travel toward the opposite side of the power source?

http://www.physclips.unsw.edu.au/jw/electricmotors.html
Check out motors and generators. Electricity will go anywhere that available, why do they want to travel there, there pushed by the voltage, or the curent down a circuit.

The lights on an airplane will work without ground.

But they sure have a complete circuit, refer to #3

(Note that AC voltage will regularly change the polarity of the terminals and the electrons will migrate one way, and then the other way, on and on.

OK, AC its pulsing the wire with a beat of 60 Hz in the USA who says that it returned? Energy is neither created or destroyed but only changes form (transforms). A law of the conservation of energy!

Who said it returns? In a Sine wave only the positive side of a graph is doing work, are you saying that the whole Bottom of the Sine wave isn't going out, or is the only thing returning? Put Time in the ?X?, put anything in the ?Y?, any measure but some measurable volume, Amp, voltage, a simple quantity, Time doesn?t return.

Note that Time is the ?X? factor in most of these equations.
http://www.physclips.unsw.edu.au/jw/AC.html#inductors

Be sure to play with all the animations most require two quick clicks to see it play!

http://www.physclips.unsw.edu.au/

When Time returns, quick we?ll bottle it and sell it, I know some people!

 

[RayS]

How in the HELL the NEC considers conduit, rigid or not, as a fault path is beyond me.

because properly installed metallic raceways are much better for fault clearing than the actual ground conductor. I do however like to see an actual ground wire for when someone knocks the pipe loose or it corrodes...

 

[RayS]

The reason you ground is because the utility has chosen to earth itself and the neutral of your transformer. That has created a return path in the earth that can kill you, but not trip a breaker at voltages below 600V.

I think lightning is the main reason the utility grounds things. Whether they should ground the secondary of your transformer would be an interesting study.

I think it'd be great if the utility did the grounding, and ran an EGC from their xfmr to the service. Then we'd have a lot less problems with stray current. I can see the need for the secondarys to be "earthed" to help voltage stability, but it doesn't do much for the consumer, just the utilities.

 

[76nemo]

because properly installed metallic raceways are much better for fault clearing than the actual ground conductor. I do however like to see an actual ground wire for when someone knocks the pipe loose or it corrodes...

If, and only if I carried a camera to every site, I could feed you your words. "Properly installed", does not mean "properly maintained". The NEC in my stupid opinion really lacks allowing raceway to be acceptable as an EGC. Quite frankly, I think it's bull.
Again, just my stupid opinion.

 

[JohnJ0906]

If, and only if I carried a camera to every site, I could feed you your words. "Properly installed", does not mean "properly maintained". The NEC in my stupid opinion really lacks allowing raceway to be acceptable as an EGC. Quite frankly, I think it's bull.
Again, just my stupid opinion.

If you feel so strongly, then make a proposal for the 2011 NEC.

 

[76nemo]

Construction vs. Maintenance

Construction vs. Maintenance

It's one thing when you personally run all the pipe. You get a helper, or apprentice, you can't guarantee anything. Wish I had a camera for all the pipe work I've seen. "He works under who's license again???" Spell that please? No thanks, give me the pipe, you grab the wire runs.
You can fix bent wire, you're screwed on pipe.

 

[roger]

76nemo, in healthcare installations, (specifically speaking of article and section 517.13) it is recognized that the metallic raceway or metallic cable sheath is the primary/superior EGC and the insulated conductor is a secondary or backup, this is regardless of who runs the conduit.


Roger

 

[chris kennedy]

This is going to get yanked

This is going to get yanked

76, relax, and above all quit using questionable language. This thread will disappear.
I stopped pressing this piont on this Forum because I can't sway enough opinions. And as per Bob, the CMP's don't care to move on this.