mechanical ground

[Anonymous]

Good morning! and like a previous poster also wish to take time to express"great web site". Where located we have sand only, and good mech ground hard to come by. Only required ground per installation of new service (200amp) is 2 grnd rod's 6' spread, 1 0n roof drip line.(per nec) There is no AHJ here, just utility co requirements for main service entrance. Read in a previous post that sometimes, TO much of a good thing may not always be true." example comes to mind it pertained to tying of romex cables(heat vs appearance).With that in mind would like to present a two part question??# 1. With above mentioned(2 rod's) would we be creating any problems or hazard's by running #4 or #6 bare copper to well casing (drill & tap//lug)and marrying with grn rods mech grnd in service panel? (hope's of gaining better ground)# 2. Also if in dwelling,where adding a sub panel,understand that neutrals and mech grnd must be kept seperate in sub panel (isolated)& beyond.(trying to keep simple)Example/ New addition to dwelling along with NEW WELL, much easier for me to run (additional ground)#4 bare to newly installed sub panel as opposed to running back to Main Panel.(this of course would all hinge on answer to question #1 if even OK.)also would marry this #4 with mech grnd in sub where fed with 4 wire sub feeder? hope I made myself clear on this. Also do you have another way of relating to mechanical ground.(EGC)? thank you when you get time! :?:

[Wgoodrich]

YOU SAID;
Good morning! and like a previous poster also wish to take time to express"great web site". Where located we have sand only, and good mech ground hard to come by. Only required ground per installation of new service (200amp) is 2 grnd rod's 6' spread, 1 0n roof drip line.(per nec)

REPLY;
The NEC requires IF AVAILABLE the following but limited to the following SEE NEC article 250.52 for complete list to be used if available, rebar in concrete, metal plates, ground rods, metal water lines in direct contact with earth, well casings at least 10' deep, and many more. All IF AVAILABLE must be connected togetehr to make the GROUNDING ELECTRODE SYSTEM. Problem is most often none is availalble at the time of the service installation. Then 250.24 tells us that the grounding electrode conductor [sole connection between the grounding electrode system and the main service] may be connected to the service neutral conductor anywhere from the point of connection at the weatherhead of the utility company to that part inside the main service rated panel which included inside the meter base. The only time two ground rods are requried serving a structure is if the first ground rod megs more than 25 ohms to ground tested by a meggar process.

YOU SAID;
There is no AHJ here, just utility co requirements for main service entrance.

REPLY;
If the NEC is adopted in your state or jurisdiction then whether there is an AUTHORITY HAVING JURISDICTION [AHJ] or not you are not forgiven from meeting the minimum safety standard requirements of the NEC.

YOU SAID;
Read in a previous post that sometimes, TO much of a good thing may not always be true." example comes to mind it pertained to tying of romex cables(heat vs appearance).With that in mind would like to present a two part question??# 1. With above mentioned(2 rod's) would we be creating any problems or hazard's by running #4 or #6 bare copper to well casing (drill & tap//lug)and marrying with grn rods mech grnd in service panel? (hope's of gaining better ground)

REPLY;
YOu may install as many recognized grounding electrode conductors that you want and you are requried connect all NEC recognized grounding electrodes listed in 250.52 together to make the grounidng electrode system. All grounding electrodes must be connected together with a GROUNDING ELECTRODE CONDUCTOR connecting them in any manner as your like but all grounding electrode conductors must be made as one entity by connection with a grounding electrode conductor sized by 250.66 of the NEC. Remember the earth is not allowed to serve as a grounding electrode conductor or an equipment grounding conductor in any manner. Wire approved and sized as a grounding electrode conductor must be installed connecting all grounding electrode conductors together making the grounding electrode system.

Be careful using a well casing. Often times a well casing is metal a few feet into the ground but plastic from that point down. This would be a lightening invite due to being in such short contact with the earth but the above short contact with the earth would not a grounding electrode recognized by the NEC. Many metal wells are just a metal well head and not a metal driven well, rather it often is a plastic driven well casing withe a short metal well head. Know what you are connecting to before you connect to it.


YOU SAID;
# 2. Also if in dwelling,where adding a sub panel,understand that neutrals and mech grnd must be kept seperate in sub panel (isolated)& beyond.(trying to keep simple)Example/ New addition to dwelling along with NEW WELL, much easier for me to run (additional ground)#4 bare to newly installed sub panel as opposed to running back to Main Panel.(this of course would all hinge on answer to question #1 if even OK.)also would marry this #4 with mech grnd in sub where fed with 4 wire sub feeder? hope I made myself clear on this. Also do you have another way of relating to mechanical ground.(EGC)? thank you when you get time!

REPLY;
The NEC requires that the equipment grounding conductor of a feeder to a subpanel must be inside the same conduit of sheathing of a cable ran with the feeder from the panel's source to the non service rated panel. You are not allowed to install a three wire cable as a feeder to a sub panel in the same building and pick up a new grounding electrode. You are required to have the equipment grouding conductor ran with the feeder from its source to the sub panel.

Your term mechanical ground is a generic slang referrance to what the NEC names to be an equipment grounding conductor. Using generic terms is an invite to be misunderstood from what you are saying.

Hope this helps

Wg

[Anonymous]

In referring to "grounding to main service "that portion is refered to as GEC, while interior system ground is refered to as EGC. Very confusing when reading about! Well system grounding understandable. Marrying GEC with Utility neutral allowed from their point of entry to main service panel.(understand) Getting back to original Question, yes would be OK to properly attach GEC to well system, since it's required if available to incoming Neutral. But the GEC is not allowed to marry with the EGC after the EGC leaves the main panel(in this case where I asked if ok to run GEC from well to sub panel for simplicity reasons,in not running all the way to other side of home where main panel located!)I have trouble here in understanding reason or what dangers are involved. I see the EGC as the fault end of the system,but apparently lose it here?? I was always under the unstanding that the EGC was the back up to the GEC(starting to sink in) if the neutral was lost from the Utility CO. If neutral is lost from POWER CO the EGC would now be the neutral in main panel bur yet in new perfectly wired Sub Panel power would be lost. With out going on I think by know you will know where my confusion is coming in. Am I right here. Also still do not understand why new GEC from well couldn't connect to sub panel. I know the two are not to be married together EGC and EGC, but WHY?? guess totally lost now. TY

[Wgoodrich]

At this point we need to clarify what a grounding electrode system is designed to do. Read the following coped section of the 2002 NEC that provide the intent of a grounding electrode system. [contact to earth] [ground rods, well casings etc.]

250.4

(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.

(5) Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a permanent, low-impedance circuit capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. THE EARTH SHALL NO BE USED AS THE SOLE equipment grounding conductor or EFFECTIVE GROUND FAULT CURRENT PATH.


Commentary;

Notice that the bold print says that the main purpose of the grounding electrode system is to be used along with the netural conductor [center tap of the transformer] to disappate a high voltage faulted current such as lightning. Remember lightning comes in unlimited power levels. Pay close attention to that last sentence I just said. HIGH VOLTAGES SUCH AS LIGHTNING! Now lets look what would happen if lightning hit you electrical system or non current carrying metallic parts such as frames of washers dryers etc. If all the grounidng electrodes [ground rods, well casings, rebar in concrete and the like are joined together before they enter into your house wiring system wouldn't this extremely high voltage exit the house a fast as possible limiting this high faulted current from passing through most of your house?

Now lets connect that extra grounding electrode [your well casing] to the sub panel. Now we have the same lightning hit the same place as discribed above. Wouldn't you be directing that lightning EXTREMELY HIGH VOLTAGE SURGE OF CURRENT not only to your primary grounding electrode system but also to that second added grounding electrode [you well casing]. When installing that contact to earth in a different location that your main service rated panel but instead in your remote sub panel didn't you just direct that EXTREMELY HIGH VOLTAGE SURGE OF CURRENT through your entire house instead of the main point of connection to earth and the center tap of your serving transformer at your main service rated panel. Didn't you just make that lightening instead of a direct path to the main service rated panel where your grounding electrode system [all grounding electrodes joined together to make the grounidng electrode system] and out of your building directly with the shortest path instead detour the path out of your house with the flow of EXTREME HIGH VOLTAGE CURRENT instead to the location of your sub panel then causing that surge of power to split and follow the feeder back to your main service rated panel where your strongest exit being your large neutral conductor connected outside your home at the center tap of your transformer with only a small part exiting out to the well casing? Your thoughts of design would cause this huge power surge to be directed throughout your home instead of out the shortest path.

If you did an experiment and I know this is going to be very disappointing but true. You could disconnect the main service neutal conductor from your transformer making your entire group of grounding electrodes serving your home making up your grounding electrode system and you would find that at best you would get a dim glow out of a few light bulbs. None of your TVs, microwaves etc. would work when using the grounding electrode system as your grounded path only.

The grounding electrode system is only able to do your any good if there is a huge surge of power such as lightning that enters your home.

Now the equipment grounding path found on the load side of your main panel that MUST BE SEPARATED from your neutral conductors anywhere after the electricity leaves the main service rated panel is there to carry short circuit faults created on that certain branch circuit to keep the current from entering the persons body using that person as a conductor of electricity.

The bare wire is only used in FAULTED conditions and only for a short period [seconds] and is designed to cause a breaker to trip due to short circuit interupting ratings of a breaker which is the second reason that a breaker will trip. The first reason a breaker will trip would be too many amps running through that branch circuit or feeder to protect the house from fire. The interrupting rating of a breaker being the second method of a breaker tripping that is designed to protect you from electrical shock.

Surely you do not want to direct the huge faulted currents through you house wiring to other locations of your house before it reaches that grounding electrode system [ground rods etc.] and the neutral conductor [center tap of your transformer outside your home]. Wouldn't you be inviting exactly that if you connected more grounding electrodes to exit elsewhere from the house other than the main service's grounding electrode system that is married to the neutral service conductor working as a team to exit from your house this huge surge of electrical power during a faulted condition.

See if the above discription can put the picture in your mind what happens in a split second when a ground fault occurs that has enough power to blow the entire end of your house into little wood or brick splinters.

The ground rods or other grounding electrodes making the grounding electrode system does not even have the capability to complete a branch circuit return path enough to light up a series of light bulbs under low current conditions. This grounding electrode system only does us any good when there is high current faulted conditions. The neutral service conductor is your big power controller of your electrical system even in lightning strike conditions. The grounding electrode system only act to augment the neutral in disappating these large surges in high current faulted conditions.

There are some other uses of the grounding electrode system such as transient voltages etc. to help keep the electricity clean but the big reason for the grounding electrode system is to be the assistant to the service neutral conductor to disappate that high surge faulted conditions.

Hope this helps

Wg

[Anonymous]

:oops: :oops: :oops: That certainly does make alot of scense and help's me in understanding. Alway's have had problem's with grounding and never asked. Theory and a good understanding of electricity is where I lack. Your discription, paint's an understandable picture, not good with book learning. Thank's very much! :D

[Anonymous]

you have now painted good picture of grounding and fault disapation. Now where I have question pertains to grounding of garage. When installing more than one circuit to garage,Nec requires, that 2 grnd rods be driven and married with EGC. Say I were to add 6 circuits and rods required married to EGC. Distance to garage is 20' vs the above asked question,were sub panel is loacated 50' away and I attached water system.(WELL) Do we not have the same situation? Wouldn't fault high voltage(LIGHTNING) then disapate insame manor?I'm going with my understanding that EGC must also be run to garage or are you not supposed to run EGC where installing grnd rods???? Thanks or am I just trying to many IF'S

[Wgoodrich]

YOU SAID;
you have now painted good picture of grounding and fault disapation.

REPLY;
Thank you, I hope that explaination sheds light to some a generic picture of neutral, grounded leg, and grounding.

YOU SAID;
Now where I have question pertains to grounding of garage. When installing more than one circuit to garage,Nec requires, that 2 grnd rods be driven and married with EGC.

REPLY;
While I agree with you that if you install more than one branch circuit in a garage you must install a panel and a grounding electrode system at that detached garage meeting the rules of 250.32 of the NEC. However I stronly disagree that the NEC requires 2 ground rods. In NEC article 250.56 specifically states that a supplemental [second grounding electrode whether ground rod or steel plate or other grounding electrode listed in 250.50 approved for use as a grounding electrode] must be added only if the first grounding electrode meg tests more than 25 ohms to ground. Unless someone tests that ground rod and proves that the first ground rod does not test less than 25 ohms to ground the the NEC does not require that second ground rod. If a ground rod megs less than 25 ohms to ground then then first ground rod fullfills the intent of the NEC. When was the last time you or you saw anyone else meg a ground rod? The NEC does not require 2 ground rods. The NEC does require that a ground rod, pipe or plate have less than 25 ohms resistance to ground.

Sorry I see that 2 ground rod stated continuously just like it is a rule of the NEC yet it never was a rule of the NEC just an accepted practice.

YOU SAID;
Say I were to add 6 circuits and rods required married to EGC. Distance to garage is 20' vs the above asked question,were sub panel is loacated 50' away and I attached water system.(WELL) Do we not have the same situation? Wouldn't fault high voltage(LIGHTNING) then disapate insame manor?I'm going with my understanding that EGC must also be run to garage or are you not supposed to run EGC where installing grnd rods???? Thanks or am I just trying to many IF'S

REPLY;
This last part said a mouth full of IFs.

If you detached garage has a noncurrent carrying path such as a metal water pipe connecting the two detached buildings connected by a common service then yes you must install an equipment grounding conductor attached to the grounding electrode system installed at each building service each separate building. You must run this equipment grounding coductor with the feeder installed between the two building being served by a common service because you have a path that current can flow during say a lightning strike being the metal water pipe etc. that connects the first buldings grounding electrode system to the second detached structure thus requiring the feeder between the two building to contain that equipment grounding conductor within that feeder. This way we have some control where that current is going [metal connection between the two buildings or the equipment grounding conductor connected between the two panels in the two buildings.

Again as said in my prior post we don't want that faulted high voltage current to enter the detached structure without a faulted current from the building with a faulted current in a remote location away from the grounding electrode system in the building receiving that faulted current. We want that shared faulted current to travel down that equipment grounding conductor that is connected close to the grounding electrode system of each panel rather than have that faulted current to travel down that noncurrent carrying metallic path such as a metal water pipe entering the nonfaulted building remote from the panel then travel through the house energizing all noncurrent carrying metallic parts such as washers dryers, ranges etc. looking for a path to earth ground duing this introduced faulted current travelinig from that detached structure with the common service. Our goal is to contain the faulted current within close proximity of hte grounding electrode system located at the panels of each building rather than traveling through the building to get to those grounding electrode systems.

NEC 250.32 requires that you marry the neutral bar and the grounding bar in the panel of that detached structure together if you have no noncurrent carrying paths between the two buildings such as metal water pipes tying the two buildings together electircal conductor wise. If there is no noncurrent carrying paths such as a metal water pipe connected between the two buildings then you may install a feeder between the two building that is without an equipment grounding conductor to serve power to that panel in the detached garage. Then this panel in the detached garage would need to be wired same as a separately derived power source as a main service rated panel marrying the neutral bar and grounding bar together as one entity.

If you have a noncurrent carrying metallic path between the two buildings then you must install an equipment grounding conductor with that feeder installed between the two buildings. When you install this equipment grounding conductor with the feeder then you connected the grounding electrode system of the first building providing its influence on the second bulding thus requiring you to separate the neutral and grounding bars in that panel installed in that detached structure. IN this case where an eqiupment grounding conductor is ran with the feeder then we need that neutral in that second building to be isolated from the grounding bar in an attempt to limit that faulted current from the adjoining building from entering that second nonfaulted building in hopes to direct the faulted current to the grounding electrode system of that second building protecting the non faulted bulding as best we can from that surge of electricity. Remember the current will take its easiest path. If that grounding electrode system is located at the location of the entry of that faulted current into the building then our hopes is that the grouding electrode system will obsorb that surge of electricity without energizing the noncurrent carrying metal such as washers dryers stoves etc. located in that second nonfaulted building that is tie to that faulted buildig by way of that metallic path connected to both buildings.

Kind of sounds like I am going in circles here but try and make the single electron that is flowing as the faulted as being the beginning of the flow and follow in your mind that electron along the easiest path and see if it is invited to go throughout the building. If you picture all that happens in a split second foot by foot of wire considering resistance and easiest path of the movement of that one faulted electron then you might get a better picture in your mind.

When you connect a well casing [not considered as available unless at that building not remote from that building] to that building then you just did the same as if you installed a ground rod instead only a better respected grounding electrode concerning the metal well casing. Just make sure that metal well casing is all metal and not just a short section of metal being the well head and the rest of that well casing being plastic.

HOpe this helps

Wg

[Anonymous]

:D My hat's off to you SIR. Can't begin to say how good you explained and took the time to get these point's across. Plan for us to reread these over and over, although you have simplified it very well. I think now where I've gone wrong always, is rather than EGS providing a way out, in my previous post's in what my understanding was then(trying to bring EGS in) Confusing even when trying to explain back to you, but now I see where my confusion always came in!!!!! I do wish to ask one more question pertaining to this issue and "THAT WILL" be the end of it. When discussing, 25 ohm megging on ground rod, by adding second rod are we saying, were adding (Better)a less resistive path for High voltage fault to pass thru? 2 more ?s come to mind and then I'm gone for good on this one, when sizing the ground is it because of service size pertaing to transformer(neutral) along with EGC sizing. Inotherwords (ahside $ cost) would'nt a #4 ground (bare) be better than where only a #6 would be required." This is it" Why Solid #8 Bare VS # 8 stranded when bonding a hot tub? Thats it and Again thank you very much. Yah made my day! :D

[Wgoodrich]

YOU SAID;
When discussing, 25 ohm megging on ground rod, by adding second rod are we saying, were adding (Better)a less resistive path for High voltage fault to pass thru? 2 more ?s come to mind and then I'm gone for good on this one,

REPLY;
The 25 ohms to ground is resistance the higher the number the higher the resistance. The higher the resistance the harder for the current to flow. The lower the resistance the more easily current will flow. The more contact of grounding electrodes the better the ease of current flow to disappate. I suspect you are questioning the long statement that only one ground rod is required unless it it proven that this one ground rod is with a resistance more that 25 ohms.
The reason that I made this long statement is that many electrical inspectors make a ruling forcing you to add a ground rod making you prove his or her ruling is wrong instead providing substantiation by that inspector to support his ruling not make you prove his ruling is wrong. In my opinion this ambiguous ruling is a violation of his or her office and statute of power.

Now do not believe that I think that a better ground or supplemental grounding electrodes are not a good thing. What I am trying to point out and hopefully a few inspectors will read this opinion is that to educate a better ground allowing the electrician or home owner to make his or her choice as to what they want would actually provide a massively better grounding electrode system on a majority of the houses being wired.

Take yourself for example, you want what is best without blowing money without reason. Normally the electricians and home owners want to wire better than the minimum safety standards set by the NEC. Inspectors are not providing the education to those they inspect on how to make that better ground greatly improved with minor monetary investment and minor time or effort invested.

In my opinion inspectors are taking a short cut quick fix to ease a conscience or convince others they are doing their jobs. If inspectors promoted education as to what is a better ground of our choices then the grounding electrode system would improve in my opinion in a surprising percentage of the wiring jobs being done especially concerning new home projects.

Lets take a ground rod and dissect its contact with earth and compare it to other options just as easily installed and some times easier to install.

Think to yourself how many electrical projects concerning new homes. Then think to yourself how many of those homes you experienced were served by these two ground rods inspectors are shoving on you that is not proven to be a valid ruling concerning the NEC.

Now consider that there is a thing in the NEC called a grounding ring. This is a #2 stranded copper conductor installed under or beside the footing of the new home when the footing is dug and poured and the foundation blocks are being installed. Think just how much it would cost to install a #2 bare stranded copper conductor long enough to reach around your home. Compare that cost to the cost of two ground rods. Now lets think just how long it would take the builder, home owner, or electrician to unroll this #2 bare stranded copper and lay it in the dirt along the bottom of that foundation wall. Think of the moisture that would be present around the footing and foundation wall. I would take a guess that this # 2 bare stranded copper wire reaching around the circumference of the footing of hte new structure would take about 10 minutes [much faster than driving two ground rods] at a cost of about $25 compared to approximately $15 for the two ground rods.

Now think of hte surface contact with earth that #2 bare stranded wire would make to the earth.

Now picture in your mind the surface available on the ground rod lets say a 1/2" ground rod 10' long. We are not talking about the thickness of the ground rod we are talking about true surface area in contact with the earth. This is all the ground rod can do in disappating current is by use of only the surface of a round ground rod. In your mind slice off the entire surface of that ground rod. Now we have a sheet of copper 10 long and approximately 1/2" wide. Now to discover the the area of square inch we would convert the 10' to 120 inches multiplied by [.5 times pie 3.14= 1.57 inches circumference. 120 times 1.57 = 188.4 square inches of area in contact with the earth.

Now lets calculate the area of # 2 copper wire approximately 175 feet that would be around the footing of the a home. The diameter of a # 2 wire is .097 times 3.14 for pie = .3 multiplied by the length of 175 feet adjusted to 2100 inches would equal 640 square inches or 4.44 square feet of area in contact with the earth. With two ground rods it would make 8.9 square feet.

You make the decision for yourself which would be better grounding electrode the famous 2 / 1/2" ground rods or a grounding ring around the footing while the trench is open. Remember a grounding ring must be all the way around a structure's footing but at least 20 feet long.

Now think of the area of square inch in contact with earth of a steel plate 2 foot by 2 foot by 1/4 inch thick. 2 foot thickx2 foot wide x.25 thick = 4 sqare feet on one side time two sides = 8 square feet of surface area in contact with the earth. With two 2 foot square steel plates you would have 16 sqare feet in contact with the earth.

The NEC 250.50 says that you must use any grounding electrodes THAT IS AVAILABLE. Wouldn't it make sense to explain in laymen's language that there are much better grounding electrodes and easier installed at comparitive prices to ground rods? Shouldn't the inspector's major responsibilty of thier position of government to provide available education as to what is safe and safer?

Making an ambiguous ruling demanding a second ground rod making you prove you meet the NEC rather than making that inspector prove NEC support of his ruling is to me a easy fix shorting the home owner the service of being told other options that would be better so that home owner or electrician can make an informed desision to provide a better option for ground rather than issuing a ruling forcing that home owner to install a second ground rod that often is beyond the minimum safety standards that inspector is supposed to enforce only.

Sorry about the speach just wanted to get a point across that there are much better choices than one or two ground rods to serve as lightning or other faulted currents protection of your home.

YOU SAID;
when sizing the ground is it because of service size pertaing to transformer(neutral) along with EGC sizing. Inotherwords (ahside $ cost) would'nt a #4 ground (bare) be better than where only a #6 would be required."

REPLY;
While some people would agree that a # 4 copper grounding electrode conductor would be better than a smaller # 6 grounding electrode conductor while serving a ground rod [made electrode], I must disagree. If you take the ground rod and calculate its ability to carry and dissipate current then compare it to the 6 awg copper grounding electrode conductor serving that ground rod you should find that the # 6 awg conductor can carry much more than the ground rod can produce in current flow. While you may install the larger # 4 conductor to serve that rod it would be much like wearing shoes two sizes bigger than fits your feet. I bigger always better? Bigger is better seems to be a popular opinion when it comes to electrical. Calculated and accurate electircal designs and proven capabilities of electrical products is much better than bigger that does nothing to improve other than to be bigger. Actually in many cases bigger can make unsafe when it comes to electrical.

YOU SAID;
This is it" Why Solid #8 Bare VS # 8 stranded when bonding a hot tub?

REPLY;
Bare is more resistive to corrosion and deteriation due to chemicals found in earth and pool or hot tub water.

Sorry about the rants in this post. I commonly experience lack of knowledge and lack of explaination and often times a quick fix when it comes to the electrical industry. This is one of the reasons that this forum has been made available. I never implied that I know it all, my hope is that others will pitch in and provide more knowledge and differing views than just my views in hopes that knowledge in the electrical industry will blossom throughout the world, knowledge when it comes to electrical may just save a life or two.

Hope this helps

Wg

[Anonymous]

Finally got time to study and try and understand.Maybe just that stupid, anyway I think what finaly sunk in with this resistance, my way of looking at before if you have one rod or half a rod the flow would be easier, but what your'e trying to tell me and as I think now I can understand.(my example) a hallway with 1 exit door and hundreds of people trying to exit(FAULT) they bunch up and go other ways, by adding doorways now they can flow out faster.(lets say another rod or system you have mentioned) Hate to take your time or sound stupid, but then some of us aren't as quick to understand and were affraid to ask. Also some teachers weren't always the easiest to understand either. Like idea of grounding, for one thing it visually could be inspected.! Would like to know how many 2' pieces of grnd rod are laying at bottom of service trucks or bottom of a lake.When you hit that unserpassible bolder under the ground??? Understand this would hold true for new work, but think you get my drift. TY again (bet u thought you heard the end of this)*

[Wgoodrich]

First we are again using the generic term ground and I really hate leaving statements open so wide as to use a generic term that could mean neutral or equipment ground. Neutral means grounded and equipment ground means grounding. Remember that last statement as I try to separate to picture stories at the same time.

When we have a large insulated neutral that is center tapped to the zero potential of hte inside of a transformer any current coming from that transformer will need RETURN path back to that transformer. The principle use of a grounded conductor [aka neutral] is to carry the unbalanced load back to the transformer that is not carried by by the hot conductor that is out of sync with the hot conductor that is carrying current out of the transformer.

Remember that you are dealing with 220 volts [2 hot wires out of sinc with each other creating 220 volts between those two hot conductors. A major part of the current taking its return path back to the transformer is taken back by the two hot conductors counter acting each other. However these hot conductors can only counter act equal value of current. Any unequal current being pulled for use with 120 volts on one hot conductor that is not also pulling equally in current on the second hot conductor has to have a path back to ground [not earth ground but zero potential ground within the transformer where the current came from] in the transformer. This uneven current being pulled by one hot conductor in excess of the current being pulled by the second hot conductor must use that grounded [aka neutral] conductor as a return path back to where it came from [transformer] The above electrical technique or operation has nothing to do with equipment grounding [aka mechanical grounding]

Now we will talk a bit on mechanical grounding. You have a bit of the picture when you are telling of one door and a hallway of people trying to get out that door. You would create a back up of people causing resistance of flow of people through that door. If there were a second door that was a bit harder to exit but could be exited then that pile of people would then look at that harder exit to be possibly of less resistant to get out than that backed up door now full of people. Then those people would flow out that second door being of less resistance than the original door is now full of people trying to get out that original door. Yes Grounding electrodes work in that manner.

However we were trying to paint a second picture here. We have places such as metal shells of dryers refrigerators etc. that we don't want exposed to this backed up flow of electrical surge such as lightning acting much like your hallway story trying to find a return path to ground [ground in this case first would be the transformer and second the grounding electrode system. Remember we are having a major power surge due to lightning in this action. We have a faulted current in this action due to the surge of the power of lightning.

Now if we had a detached garage hit by lightning we would not want that surge of power to seek the path to ground that the neutral conductor could not handle to travel to our main house to get to disapate into the earth. We would rather have it have a path at the detached structure instead of our main house that didn't get hit by the lightning. If we did not have a grounding electrod installed at the detached structure then that surge of power in excess that the ground can handle would then have to go to the house grounding electrode system. This is why we want a grounding electrode system at the detached structure to provide the least resistance to a path to ground [earth] at that detached structure. This invites the current not to go to the house as best we can. Remember there is a neutral conductor in this feeder between the main house and the detached structure. This neutral will take a certain amount of this faulted current back to the transformer yet it is insulated. Excess current that this larger insulated neutral conductor can not handle we want to try and disapate at the detached structure rather than induce this surge of current into the main house. If the lightning charge is big enough it will go everywhere and meltdown almost everything. Our design is an attempt to handle the surge of hte smaller lightning strikes that are more common and more managable where we can make a differnece by guiding that surge of power where we want as best we can. Smaller surges of lightning are more common and more able to be influenced.

Now we will talk about what would happen if you installed a grounding electrode at the sub panel in the main house remote from the main panel of that same house. If no grounding electrode is intalled at that sub panel but an equipment grounding conductor is installed between the main panel and the sub panel then if a short appears at the sub panel the current will flow to the main panel where the grounidng electrode system is located as well as where the insulated neutral conductor is located that is planned to take a major part of this lightning surge. This surge appearing at the subpanel will travel to the main panel along the same path as the neutral already carrying a major part of that surge because there is no other outlet at that subpanel unless you improperly installed a ground rod at that sub panel. Now you ask why then wouldn't we want to install that grounding electrode at that sub panel so the current did not travel through the house were we are living. The reason will become obvious coming up. The sub panel is a small electrical slave component of the main panel where the power normally is coming from and wiht the knowledge that the main service panel has the best set up of the grounding electrode and main service neutral conductor connected directly to the transformer to handle any of this electrical surge of lightning.

Now that you have a picture the best set up is the main panel to handle this surge of lighting and the smaller sub panel is less capable with much smaller feeders than the service conductors in the main service panel. If you did not install that grounding electrode at that sub panel as your are forbidden to do then you have not invited any massive surge of lightning to travel into and through the living part of the home to get to that subpanel because there is no outlet there such as the grounding electrode that you did not install at that sub panel following the rules of the NEC. YOu are directing that surge of power out of the house through the largest cables of the house and the grounding electrode system all located at that main service panel. This design with no ground rod at that sub panel would direct current out of hte house instead of through the house if the surge hits in the area of the main service panel. Our hopes are to keep this electrical surge of lightning power from passing through the house instead pass outside through our best largest conductors at the main panel closest to the transformer.

If you installed against NEC rules a grounding electrode [normally a ground rod or well casing] then you just directed that power surge through the house where you are rather than out of the house on the at the main panel. The surge of power is so accessive it would take advantage of both the grounding electrode system as required to be installed at the main panel and also travel through everything in the house trying to get to that second grounding electrode that you installed remote from that main service and at the sub panel.

Strarting to make a picture in your mind as to what we want and what we don't want to happen and when concerning faulted currents or lightning strikes?

Wg

[6pack]

think I'm getting good picture now and will re and reread. The discussion leads to understanding of 4 wire cords now required on appliances, leading to one less question!Would like to repeat my understanding of detached building wiring, If 10' non current pipe enters building(In earth) a EGC is required to run with feeder.(more than 1 circuit) and isolate neutral from EGC same as if it were inside sub in main dwelling and install 2 grd rods and marry with EGC. If no non current carrying path between buildings(more than 1 cuicuit) we do not carry EGC from main dwelling, But create our own with 2grnd rods and marry with neutral. Hope I have this right, my main thing in all of this was the REASONING! which I feel I have now, just can't explain right all the time . TY very much One thing wanted to clerify in bonding grid on hot tub did we say you can use EITHER bare solid or stranded #8. You think you were going in circles cant sleep here!

[Wgoodrich]

You are confusing the difference between a GEC and a EGC.

GEC is a grounding electrode conductor that is that sole conductor between the ground rod or metal water pipe in direct contact with the earth serving as the required grounding electrode source to serve the building if in direct contact with the earth.

EGC is an equipment grounding conductor that comes from the inside of a panel and is installed with a feeder or branch circuit.

YOU SAID;

Would like to repeat my understanding of detached building wiring, If 10' non current pipe enters building(In earth) a EGC is required to run with feeder.(more than 1 circuit) and isolate neutral from EGC same as if it were inside sub in main dwelling and install 2 grd rods and marry with EGC.

REPLY;
THIS IS INCORRECT. If the 10' of noncurrent carrying metal pipe enters a building then that is entirely different from a metal water pipe that connects as a noncurrent carrying metallic path between the two buildings.

If you have a metal pipe connecting the two buildings together then you MUST KEEP ALL EQUIPMENT GROUNDING CONDUCTORS AND THE GROUNDING ELECTRODE CONDUCTOR ISOLATED FROM ANY WHITE INSULATED NEUTRAL CONDUCTOR AND THE PANEL NEUTRAL BAR. If you have the metallic noncurrent carrying metllic path connecting the two buildings creating an electrical path between the two buildings then in that accessory building the neutral is never to touch the grounding system at all.

If you have a metal water pipe in direct contact with the earth [even that noncurrent carrying metallic pipe ran from the main building to that accessory building if a water pipe and in direct contact with the earth entering that accessory building then you must connect a two piece ground clamp within 5 feet of where it enters that accessory building and then run a grounding electrode conductor [sole conductor connecting the grounding electrode to the grounding bar of the panel serving that accessory building]. You must install that grounding electrode conductor from that two piece clamp installed within 5' of the metal water pipe in direct contact with earth and run that grounding electrode conductor to that grounding bar in that accessory building's panel.

You are talking the same pipe but different usage. The clamp within 5 feet of where that metal water pipe in direct contact with earth entering that building is being used as a grounding electrode creating a grounding source for that building. The wire connecting between that two piece clamp and that panel is a GEC grounding electrode conductor. That metal pipe in this action is using that metal pipe in direct contact with the earth as a grounding source. In doing this grounding electrode conductor and the grounding source does not tell you to separate the neutral and grounding bar and does not tell you to install the equipment grounding conductor EGC between the two buildings with the feeder. The fact that this metal water pipe is connected to both buildings if indeed it does connect between the two buildings makes you run that equipment grounding conductor between the two buildings ran with the feeder and then you must isolated the neutral only if that metal pipe connects to both buildings.

We are dealing with two concerns GEC grounding electrode conductor AND EGC equipment grounding conductor. Two different concerns not related to each other. You may have a metal water pipe in direct contact with the earth but not connected between the two buildings and you must marry the neutral bar to the grounding bar. ONLY IF that metal pipe connects both buildings do you have to install the equipment grounding conductor with the feeder between the two buildings and ONLY if this equipment grounding conductor is ran with the feeder between the two buildings do you isolate that neutral bar from that grounding bar in that panel in that accessory building.


YOU SAID;
If no non current carrying path between buildings(more than 1 cuicuit) we do not carry EGC from main dwelling, But create our own with 2grnd rods and marry with neutral. Hope I have this right, my main thing in all of this was the REASONING! which I feel I have now, just can't explain right all the time .

REPLY;
This is where you are mixing a GEC and a EGC. You may have a metal water pipe that does not touch both buildings. Then again that metal water pipe may touch both buildings. Whether this metal water pipe touches both buildings or not you must use this metal water pipe as a grounding electrode [same as a ground rod] as a grounding source. Then only if this metal water pipe touches both buildings are you required to install that equipment grounding conductor with the feeder between the two buildings also making you isolate the neutral from grounding everywhere in that accessory. building. If you have a metal water pipe that does touch earth for 10 feet but does not touch both buildings then you still would marry the neutral bar and grounding bar.

Then again you may install that equipment grounding conductor with the feeder between the two buildings at any time or condition. You may voluntarily install that equipment grounding condcutor with the feeder btween the two building whether you have that noncurrent carrying metallic path or not. NO MATTER THE REASON FOR INSTALLING AN EQUIPMENT GROUNDING CONDUCTOR WITH THE FEEDER BETWEEN THE TWO BUILDINGS YOU STILL MUST ISOLATE ALL NEUTRAL BARS OR CONDUCTORS FROM EQUIPMENT GROUNDING CONDUCTORS OR BARS IF YOU INSTALL THAT EQUIPMENT GROUNDING CONDUCTOR WITH THAT FEEDER BETWEEN THE TWO BUILDINGS.

The master point is that equipment grounding conductor ran with the feeder between the two buildings. Whether voluntary or due to a noncurrent carrying metallic pathe existing between buildings if you install an equipment grounding conductor with that feeder between the two builtinds then you must isolate all neutrals form grounding in that accessory building.

The feeder [equipment grounding conductor] dictates whether you isolate the neutrals from grounding in that accessory building.


YOU SAID;
TY very much One thing wanted to clerify in bonding grid on hot tub did we say you can use EITHER bare solid or stranded #8. You think you were going in circles cant sleep here!

REPLY;
Must be solid copper and not stranded copper bonding grid wire in pools and hot tubs. Insulated or bare does not matter except if in a conduit directly connected to an underwater light fixture. If this 8 awg bonding grid wire is connected inside the wet niche of an underwater light that wire must be not only solid but green insulated. [exposed to chemicals of water in pool or hot tub]

Hope this helps

Wg

[6pack]

,in rereading my post I may have not made myself clear, I did mean that metal pipe to be the water pipe.somehow in reading & Rereading your reply in parts I'm not sure but think your thinking I'm running feeder in conduit?? I understand GEC to be Water pipe and ground rods,grouding Electrode conductors.EGC to be equipment grounding conductor for feeders or branch circuits. along with neutral,EGC & GEC to make up the GES in main panel. Along with understanding lightning faults(Maybe little fuzzy yet) So I will try again. If wiring detached garage with more than one circuit(forget water pipe for now) (60ampfeeder)will run UF cable 3#6 plus #10(EGC) (6 cir without main) Isolate neutral from the panel and GEC & EGC. 2 grnd rods (GEC) continuous #6 bare to panel ground bar and marry with EGC. All branch greens or bares then connect to ground busbar. WATER PIPE if connected between both buildings the EGC must be run with feeders and GEC run between W/P and grnd bus bar. Also if unattached water pipe enters garage it also must be(GEC) married with grnd busbar. END POST ONE

[6pack]

Gotta get to end of this just want to know I know. Now if we have no noncurrent paths between, we can run a feeder without the EGC and treat the panel as a main service panel by marrying neutral with GEC and panel. Assume running in PVC. Hope I'M right this time??? Nothing mentioned here about conduit or did I miss something, If I did can you run this by me If were to run in Conduit to tired. If you were to use conduit. IMC and ridgid comes to mind would assume EGC would be required and wire according to past mentioned connections. Tired but sure will make me feel good with all I've learned here. Thanks ever so much. Grouding more difficult then being married.

[Wgoodrich]

Sometimes a picture will help pick up different possibilities in the wiring design that we are not communicating to each other. I added this drawing in hopes to ensure that you are catching the different small differences that changes the rules pertaining when a grounding electrode is required with the feeder and when it is voluntary. Then it is important to me that you catch that any metal pipe that is available that is in direct contact with the earth for a minimum of 10' regardless whether it connects the two buildings or not must also be used as a ground rod [grounding source] also.

We have two rules that are working at the same time that sometimes gets molded together and misunderstood. Try the following picture that may help.

wannabbee I really don't care if this post goes on for a month as long as the results of accuracy and the quest for knowledge you seek is obtained in the end. We have a desire to help understanding of electircal and reasons for required or desired electrical designs. YOu ask what you feel you need to ask. YOu are doing fine. So many other people are riding along with this discussion and not only you are picking up knowledge. We also have many that are in the know that will jump in if they disagree with what I am saying. That is our watch dog protection for accuracy. Many issuing replies in this forum are quite skilled. We tend to watch each other for accuracy and we all have no problem with being questioned on that accuracy. The goal is to help accurately for all with the learnig quest in mind.

You are doing fine.

Wg

http://www.homewiringandmore.com/storage/forumanswerpics/twobuildingsgrounding.jpg

[6pack]

Got it now along with numerous other items discussedCertainly will reread these posts and reread. Wish to thank you again for your help and patience. It's nice know why your doing! rather than just doing! Took many years(many) till now to understand properly! I hope that if there are any apprentices out there checking your sight,appreciate what you can do to help them. GUYS if your journeyman can't answer your questions or take the time(BOSS). See your APPR Adviser. Hey! Tank's ah bunch :D

[Wgoodrich]

Good Luck till next time.

Wg