To ground or not to ground...

Roy Q.T. wrote:


Roy The code does not forbid the bonding of the neutral to ground on the load side of the Service Disconnecting Means in all cases. There are several specific exceptions and buildings supplied from a service located elsewhere is one of them.
Characterizing my response to another posters questions as harassment is an interesting bit of hyperbole.
As for challenging a code official I have done it several times. The vast majority of the electrical inspectors I have dealt with have been consummate professionals. When I encounter one that is not knowledgeable or who substitutes personal preference for adopted code I do call them on it. Appointment as a code enforcement official does not make anyone infallible. In the course of thirty five years in electrical work I have had a few inspectors insist on things like: plastic boxes in runs of metallic cable or raceway without any bonding means in the boxes, the installation of a service rated fused switch ahead of a fire pump controller that was listed as "suitable for use as service equipment", the installation of a main breaker in a twelve slot panel being used as service equipment with five double pole breakers installed on the grounds that two single pole breakers could be installed that would raise the number of breakers to more than the permitted maximum of six, and several more. Inspectors are just human beings who are doing very important work. They can make mistakes just like anybody else.
I would much prefer being a nuisance than siting idly by while unqualified advice is given that will endanger the person receiving it.
I cannot see how I should be embarrassed in any way by having seen a number of electrical injuries and deaths in the course of over thirty years of service as a volunteer fire fighter / rescuer. Am I supposed to be ashamed that I crawl into the buildings that most folks run out of?
If you are going to criticism another fellows writing it would behoove you to make sure that your criticism is written intelligibly. That last bit isn't even a complete sentence. -- Tom H
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Re: To ground or not to ground. attn:--Mr. Tom H. Group: alt.engineering.electrical Date: Fri, Mar 25, 2005, 10:40pm (EST+5) From: snipped-for-privacy@verizon.net (TakomaParkVolunteerFireDepartmentPostmaster) Roy Q.T. wrote: Mr. Tom H I already Stated the code that Prohibits Grounding the Neutral at a Subpanel of a System that is already Neutral/Grounded at the Service Disconnect, Yet you insist in Harassing Mr. Tarin & Other here into believing your way is the Only correct way. FURTHERMORE: You are even Challenging the Code Inspectors Decision (Not Good Form Fellow) as if your concern for Life is some how Greater than His that is His Job in his specific Field to Prevent the Lose of Life and Oversee Electrical Ethics. Other than charge you as a Nuisance: With All Due Respect To Many Cases of Death By Electrocution you've seen in your Career., I, in my 28 years in the Field Have Not Caused Ever a single Shock Much Less the displeasure of Witnessing a Death so Horrific, as it apparently is Custom with your Fellow WorkClass Men., Nor Have any of The Men from my Training Academia Ever Suffered a Single Death due to Improper Handling or Design of an Electrical System. If your Workmanship is anything close to the poor writing skills I've noted in you here today and that you've so Egregiously Displayed here., You should only Be Concerned about Yourself and Seek Professional Help & Counselling. Your Replies are Alarming and Unfounded., only of your Lack, of Ethics Towards Others & Security in your Profession. Sincerely: Roy Q.T Roy The code does not forbid the bonding of the neutral to ground on the load side of the Service Disconnecting Means in all cases. There are several specific exceptions and buildings supplied from a service located elsewhere is one of them. Characterizing my response to another posters questions as harassment is an interesting bit of hyperbole. As for challenging a code official I have done it several times. The vast majority of the electrical inspectors I have dealt with have been consummate professionals. When I encounter one that is not knowledgeable or who substitutes personal preference for adopted code I do call them on it. Appointment as a code enforcement official does not make anyone infallible. In the course of thirty five years in electrical work I have had a few inspectors insist on things like: plastic boxes in runs of metallic cable or raceway without any bonding means in the boxes, the installation of a service rated fused switch ahead of a fire pump controller that was listed as "suitable for use as service equipment", the installation of a main breaker in a twelve slot panel being used as service equipment with five double pole breakers installed on the grounds that two single pole breakers could be installed that would raise the number of breakers to more than the permitted maximum of six, and several more. Inspectors are just human beings who are doing very important work. They can make mistakes just like anybody else. I would much prefer being a nuisance than siting idly by while unqualified advice is given that will endanger the person receiving it. I cannot see how I should be embarrassed in any way by having seen a number of electrical injuries and deaths in the course of over thirty years of service as a volunteer fire fighter / rescuer. Am I supposed to be ashamed that I crawl into the buildings that most folks run out of? If you are going to criticism another fellows writing it would behoove you to make sure that your criticism is written intelligibly. That last bit isn't even a complete sentence. -- Tom H ---------------------- I had withdrawn from this discussion but seems more than pride is at risk here.
Oh it's a sentence alright, (stick to fighting fires at least there we have supervisors)
You have a lot of gumption coming here bad mouthing the electrical advice when it's you that is endangering others here, I admire your where eagles dare courage when entering a bldg I go out of y way for others too, but just as you think inspectors, so do I of firefighters, you can make a mistake too, claim all you want heck keep your job as a firefighter but don't come here preaching electrical morality in your briefs; the fact is a short circuit is a short circuit, the code cautions against bonding the neutral at a subpanel, though Mr.Tarins panel is a full panel with Main Breakers he is using it as an alternate or subordinate point & distribution panel in his Cabin, you got to be out of your Flippin Mind suggesting he bond the Neutral there. I respect firefighters despite the fact i once had to stop a fireman from hitting an irrate woman with a taser, he would've got past me but i raised my voice about the gasoline she had doused herself with and the batallion commander ordered him out. wish I could have the same done here };-)
If you can explain how this short circuiting the Ground & Neutral Buss Bars to one another in His Household Panel is The Safests Approach to Wiring his Cabin and convince Me, The Inspector, Others here & Ultimately Mr. Tarin, this could conclude with some sound advice for the tarins. (it is my experience the shortcircuit will trip the breaker constantly until removed)~if your lucky and evertything is grounded & connected properly.)
Roy Q.T.
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| I already Stated the code that Prohibits Grounding the Neutral at a | Subpanel of a System that is already Neutral/Grounded at the Service | Disconnect,
You guys may be talking about 2 different things. Absent a specific example, I can't say who's statement is more right than the other. Still, I've seen cases where neutral and ground are double bonded and everyone insists it is right (bonding at the meter and at the service entrance), and it drives me nuts to see it that way.
| Yet you insist in Harassing Mr. Tarin & Other here into believing your | way is the Only correct way.
It is common on Usenet for people to stand their ground (pardon the pun) with differing opinions.
| FURTHERMORE: You are even Challenging the Code Inspectors Decision (Not | Good Form Fellow) as if your concern for Life is some how Greater than | His that is His Job in his specific Field to Prevent the Lose of Life | and Oversee Electrical Ethics.
A small minority of code inspectors genuinely need challenging. Someone needs to stand up and put them in their place. Not everyone has the guts to do so.
In all cases, you do have a right to know what code the inspector is using to fail some part of the installation. He should be able to cite specific NEC and/or local code, and you should be able to look that up and see what he is talking about.
FYI, I once had an inspector fail some work done by an electrician we hired, and not indicate even what aspect of the work failed. I had to get the city legal cousel called in to just get this tid bit of info. Once I knew what was wrong, it could be fixed. He came back and passed it.
--
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| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
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wrote:

The *original* question wasn't about 'double-bonding' though. To me, that is connecting the neutral to the *same* ground system in two different panels. And that is generally bad.
The *original* question was a service panel feeding a separate building. The feed to the separate building consists of two hots and the neutral (only a 3-wire feed). The feed to the separate building does *not* include the ground (EGC). The separate building has *no* conductor (not even pipes) that connect to the first service panel. So it is two *separate* ground systems. Bonding one grounding system to neutral at the service entrance is okay. And so is bonding a *separate* ground system to the neutral in the separate building.
In this circumstance the code *clearly* allows for bonding the EGC of the separate building to the neutral *and* installing two grounding rods for the separate building's EGC.
In this type of installation it is safe to bond the EGC to the Grounded Current-carrying Conductor ('neutral') in the sub-panel because the grounding system in the separate building is *separated* from the grounding system at the main service entrance, there will be very little current flow diverted from the neutral conductor between the buildings.
Diverting neutral current in a sub-panel, into a single grounding system that re-connects to the neutral in the main service is what needs to be avoided. But with no interconnection between the separate building and the service panel, this isn't a problem.
The purpose of the EGC system is to help maintain the frame/exposed parts of portable equipment and appliances at a potential as close to the *local* earth potential as possible. This minimizes the hazards to people standing on 'earth' and touching said appliances. This is why it is preferable to have the EGC connected to local grounding rods if it is an electrically separate grounding system.
If bonding the neutral to the EGC in a sub-panel can create multiple pathways for neutral current to return to the main service, then it must be avoided by *not* bonding neutral and ground locally in the sub-panel. In that situation, the sub-panel's EGC bus-bar can have a significant potential above the earth where the grounding system actually contacts earth. And that can be a hazard to people standing on earth and touching an appliance's frame connected to the sub-panel's EGC. But that wasn't the case in the *original* question.
daestrom
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Re: To ground or not to ground. attn:--Mr. Tom H. Group: alt.engineering.electrical Date: Tue, Mar 29, 2005, 10:34pm (EST+5) From: daestrom@NO_SPAM_HEREtwcny.rr.com (daestrom)
wrote: | I already Stated the code that Prohibits Grounding the Neutral at a | Subpanel of a System that is already Neutral/Grounded at the Service | Disconnect, You guys may be talking about 2 different things. Absent a specific example, I can't say who's statement is more right than the other. Still, I've seen cases where neutral and ground are double bonded and everyone insists it is right (bonding at the meter and at the service entrance), and it drives me nuts to see it that way. The *original* question wasn't about 'double-bonding' though. To me, that is connecting the neutral to the *same* ground system in two different panels. And that is generally bad. The *original* question was a service panel feeding a separate building. The feed to the separate building consists of two hots and the neutral (only a 3-wire feed). The feed to the separate building does *not* include the ground (EGC). The separate building has *no* conductor (not even pipes) that connect to the first service panel. So it is two *separate* ground systems. Bonding one grounding system to neutral at the service entrance is okay. And so is bonding a *separate* ground system to the neutral in the separate building. In this circumstance the code *clearly* allows for bonding the EGC of the separate building to the neutral *and* installing two grounding rods for the separate building's EGC. In this type of installation it is safe to bond the EGC to the Grounded Current-carrying Conductor ('neutral') in the sub-panel because the grounding system in the separate building is *separated* from the grounding system at the main service entrance, there will be very little current flow diverted from the neutral conductor between the buildings. Diverting neutral current in a sub-panel, into a single grounding system that re-connects to the neutral in the main service is what needs to be avoided. But with no interconnection between the separate building and the service panel, this isn't a problem. The purpose of the EGC system is to help maintain the frame/exposed parts of portable equipment and appliances at a potential as close to the *local* earth potential as possible. This minimizes the hazards to people standing on 'earth' and touching said appliances. This is why it is preferable to have the EGC connected to local grounding rods if it is an electrically separate grounding system. If bonding the neutral to the EGC in a sub-panel can create multiple pathways for neutral current to return to the main service, then it must be avoided by *not* bonding neutral and ground locally in the sub-panel. In that situation, the sub-panel's EGC bus-bar can have a significant potential above the earth where the grounding system actually contacts earth. And that can be a hazard to people standing on earth and touching an appliance's frame connected to the sub-panel's EGC. But that wasn't the case in the *original* question. daestrom ------------------------ let me see if i got understood you,
we agree the systems are seperate but for the 3wire underground conductors, you say, since no bonding conductor was transfered over from the service disconnect it is Ok to bond the Neutral & EGC {{{but with Seperate Grouding Rods}}} =[do i have you right this far?] not useing the jumper tag inside the panel, Right? I think the bonded Neutral that runs from the Cabin to the Meter/Service Disconnect at the Pole is a pretty strong path for current ( wouldn't you say) If He were to Bond That Neutral conductor from the Cabin to Earth to The EGC Buss via the supplied jumper as others suggest in my book would create a hazard.
the *original* question was to ground bond with EGC to the EGC Buss in His Cabins Panel with an Isolated Neutral from the Pole., somehow he is lead to believe He must bond the Neutral Bar as well as the Cabinet EGC Bar, My Point is He should Bond the EGC Buss to Earth with A groudning Electrode and not to the Neutral which is apparently bonded at the service entrance.
I am witholding my opinion on the Neutral/EGC Buss being bonded [commentaries] in light of them being grounded WITH SEPERATE GROUNDING ELECTRODES as Daestrom pointed out.
* This technique is beyond me, since I have never seen this done.
oy
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<snip because your webtv doesn't properly quote or attribute>

No. In the second, separate building, the sub-panel is wired *just like* it was a primary service. It has a pair of ground rods outside connected by large bare wire to the grounding bus inside the panel. The three wires from the other 'building' (two hot and neutral) are connected into the panel just like a main service entrance. The neutral and ground busses *are* jumpered right in the panel.

No, that does not create a hazard. The neutral coming into the building from the 'other building' is treated *just like* a primary service. In a simple, single-panel service drop, the neutral is grounded by the utility at the pole, and run into the main service panel where it is jumpered to the ground bus. And that ground bus has an independent connection to local grounding rods.
This is the same thing. You have three conductors, one of them happens to be grounded at the other end. It comes into the panel and the neutral and ground busses are jumpered in the same manner.
The only hazard would be if you carried the *fourth* wire to the second building *and* jumpered it to the neutral at this sub-panel. Then the neutral current would have *two* conductors about the same size to flow back to the main service panel. And that would raise the potential on the sub-panel's ground bus.

And that is correct. He should. With separate grounding systems in the two 'buildings', they should *both* be jumpered to the neutral bar.

And as several of us have tried to explain, your position is wrong. The EGC buss in the sub-panel should be bonded to ground through appropriate ground rods, *and* bonded to the neutral.
If he has a grounding system in the cabin that is *not* jumpered to the neutral bus *at the cabin*, and the cabin grounding system is *not* connected back to the main service panel via a fourth conductor, *then* there is a hazard. With your suggested setup, a faulty appliance that connects a hot lead to ground will not carry significant current (limited by actual resistance of the earth between cabin and main service). Such a fault will *not* trip a circuit breaker and the frame of such a faulty appliance will go undetected. If touched by a user, the current thru the user to ground may be hazardous (the resistance of the earth between cabin and main service can sometimes conduct enough to be lethal).
daestrom
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wrote:
| The *original* question wasn't about 'double-bonding' though. To me, that | is connecting the neutral to the *same* ground system in two different | panels. And that is generally bad. | | The *original* question was a service panel feeding a separate building. | The feed to the separate building consists of two hots and the neutral (only | a 3-wire feed). The feed to the separate building does *not* include the | ground (EGC). The separate building has *no* conductor (not even pipes) | that connect to the first service panel. So it is two *separate* ground | systems. Bonding one grounding system to neutral at the service entrance is | okay. And so is bonding a *separate* ground system to the neutral in the | separate building. | | In this circumstance the code *clearly* allows for bonding the EGC of the | separate building to the neutral *and* installing two grounding rods for the | separate building's EGC.
IIRC, it *requires* it.
| In this type of installation it is safe to bond the EGC to the Grounded | Current-carrying Conductor ('neutral') in the sub-panel because the | grounding system in the separate building is *separated* from the grounding | system at the main service entrance, there will be very little current flow | diverted from the neutral conductor between the buildings.
As long as there are no other metallic paths between the buildings that could lower the ground impedance between them. If there are, feeding the grounded conductor can become mandatory, or isolate it with a transformer.
| Diverting neutral current in a sub-panel, into a single grounding system | that re-connects to the neutral in the main service is what needs to be | avoided. But with no interconnection between the separate building and the | service panel, this isn't a problem.
Absolutely. This isn't about neutral current on high impedance earth ground, but on a distributed EGC, exposing people to voltages.
| The purpose of the EGC system is to help maintain the frame/exposed parts of | portable equipment and appliances at a potential as close to the *local* | earth potential as possible. This minimizes the hazards to people standing | on 'earth' and touching said appliances. This is why it is preferable to | have the EGC connected to local grounding rods if it is an electrically | separate grounding system.
For a stick building (a typical home) what about additional ground rods at locations distant from the main panel, with the groundING wire also connected to them (but not the groundED wire). To prevent lightning and earth current issues, these separate ground rods should also be connected with something like a ground ring.
I plan to put a heavy ground ring around my house with rods at 12 points and 24 or more radials.
| If bonding the neutral to the EGC in a sub-panel can create multiple | pathways for neutral current to return to the main service, then it must be | avoided by *not* bonding neutral and ground locally in the sub-panel. In | that situation, the sub-panel's EGC bus-bar can have a significant potential | above the earth where the grounding system actually contacts earth. And | that can be a hazard to people standing on earth and touching an appliance's | frame connected to the sub-panel's EGC. But that wasn't the case in the | *original* question.
And a transfer switch _downstream_ of the neutral bonding (of both feeds) would have to switch the neutral instead of solidly connecting it, else the bonding in the other feed will make an extra neutral to EGC path and put current on the EGC. And of course such a transfer switch must be sure that the disconnect timing cannot disconnect the neutral first or connect it last in either position (for example the neutral blade might be larger or the terminals raised up).
--
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| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
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It seems we All don't agree on one single method of Grounding this Cabin.
I read that if you Bond the Neutral to a Ground Bonding Electrode where there is to be a seperate EGC Bonding Electrode they must be 1200-1400 ft apart. wouldn't you say the 300ft from the Electrode at the pole is enough Neutral Bonding,
You don't have a Processing Plant in there do you Mr. Tarin };-) ?
like Phil I agree that Bonding the Neutral to the Equipment at the Cabin would expose the people there to shocks.
oy
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O.K. Guys...here's the latest.
The power company connected to my meter base yesterday. The lineman providing the service has his Masters in Electrical Engineering and has been working on this stuff for a long time.
I described my setup to him and asked him about the grounding/bonding issue. He very kindly examined my setup and stated categorically that I had performed a perfect installation that was to code. (He even complimented me on my wiring job).
My installation:
1. Meter Base: 200 AMP disconnect with feed-through lugs. Neutral Bonded to Ground. (Grounding Electrode)
2. Subpanel on Cabin: 4/0, 3-conductor feed. Neutral Bonded panel and to Ground via the buss bar.
3. Grounding System at Cabin: 2 - 8ft. grounding electrodes connected by #4 bare wire buried @2ft., Copper Plumbing (about 15 ft. underground) bonded to electrodes.
He said that everything was bonded and grounded correctly, and to code.
One Proviso: He indicated that since we live in a lightening prone area, that it would be a good idea to not bond the plumbing lines, even though it is recommended in the NEC. I'm not sure I understand the reason why. Other than that....A.O.K.
Question: He measured the voltage potential at the meter and it registered at 244 volts. At the cabin he measured it again and it registered at 246 volts...an increase???!!!
What gives?
Randell Tarin

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Yes, often homeowners will take more time and care to do an above average job. I'm glad you resolved your problem *and* had it properly inspected. Now you *know* the job is done right :-)
daestrom
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Hey I got it right, I had figured it out when Mr. Tarin told me he had main breakers on his panel, i asked him to run that by the inspector again with the specific detail, in fact it was not a subpanel as mentioned.
can anyone explain the extra 2 volts measured at the cabin?
AND: That's a wrap ....
oy
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The line voltage varies over time. A 2 volt difference (1%)is trivial. I would assume when the cabin registered 246 volts the meter was at a higher voltage. Bud--
tarin wrote: > Question: He measured the voltage potential at the meter and it registered

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has been

What's a guy with 6+ years University education doing running around with tools? Plus the time it takes to get a journeyman's licence..
Bill
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Perhaps 'tarin' misunderstood and the guy is a 'Master Electrician', not a a MS degree. He would be quite qualified to make the inspection and pass judgement on tarin's installation then. Actually, a MS in EE does *not*, in and of itself qualify him to make such an inspection.
daestrom
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Well wonders never cease to amaze me, I got a call from a lady friend with a no lights problem, the panel was open cover on the floor, someone had done some work and disconnected and connected new stuff, he had 2 wires in a CB one of them was not secured as usual in such bad CB connections., I spliced them together & fixed the problem, But, Low & Behold I saw the Neutral Grounded to the Panel, Big as Day };-) so, there's a first for Everything & Everyone., it was a garage installation ...Thanks for putting up with me :-)
oy
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HorneTD Wrote:

Roy Q.T. wrote:

Roy I will say again that I mean you no harm but I will not be silent while you advise others to do things that will endanger them and their families. There is no place in the code that will allow you to use the earth as the only Equipment Grounding Conductor (EGC). Whenever a building is supplied by a circuit that does not include an EGC the code requires that the neutral be bonded to the disconnecting means and the grounding electrode system at that building. You have said repeatedly that the code does not permit this and you are plain wrong.
What you cannot do is quote a section of the code that permits what you are suggesting which is to leave the GECs in the home with no pathway back to the source of supply other than the earth which is specifically forbidden by the code. It may not be possible to make the OPs installation entirely code compliant, because in the absence of a separate Equipment Grounding Conductor (EGC) in the feeder the neutral is the only low impedance path back to the source of supply, but it is possible to make it reasonably safe. All I and others here are asking you to do is to justify the installation you suggest. Can you reconcile your proposed installation to section 250.4 General Requirements for Grounding and Bonding.
250.4 General Requirements for Grounding and Bonding. The following general requirements identify what grounding and bonding of electrical systems are required to accomplish. The prescriptive methods contained in Article 250 shall be followed to comply with the performance requirements of this section. (A) Grounded Systems. (1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation. (2) Grounding of Electrical Equipment. Noncurrent-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth so as to limit the voltage to ground on these materials. (3) Bonding of Electrical Equipment. Noncurrent-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path. (4) Bonding of Electrically Conductive Materials and Other Equipment. Electrically conductive materials that are likely to become energized shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path. (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 not be used as the sole equipment grounding conductor or effective ground-fault current path.
Take special note of the last sentence. It specifically forbids using the earth as an EGC of fault clearing pathway.
In addition to suggesting that the EGCs in the home be left without any low impedance pathway back to the source of supply you have suggested that the interior metallic plumbing not be bonded to the neutral. In the absence of a EGC in the feeder bonding of interior metal piping systems is required by 250.104 Bonding of Piping Systems and Exposed Structural Steel.
250.104 Bonding of Piping Systems and Exposed Structural Steel. (A) Metal Water Piping. The metal water piping system shall be bonded as required in (1), (2), (3), or (4) of this section. The bonding jumper(s) shall be installed in accordance with 250.64(A), (B), and (E). The points of attachment of the bonding jumper(s) shall be accessible. (1) General. Metal water piping system(s) installed in or attached to a building or structure shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or to the one or more grounding electrodes used. The bonding jumper(s) shall be sized in accordance with Table 250.66 except as permitted in 250.104(A)(2) and (A)(3).
Now go back to the language in section 250.4 General Requirements for Grounding and Bonding. How does the installation that you have proposed and defended meet the requirement for an effective ground-fault clearing path.
I'm an electrician by craft for my bread work. I only brought up my service as a volunteer fire fighter / rescuer to explain why I had seen several electrical injuries and two electrocutions rather than to hold myself up as some paragon of virtue as you seem to imply. In over twenty years of service on ambulances and thirty in fire service I have seen quite a few of the ways that people get injured and killed.
I have done electrical work for nearly forty years in places as diverse as Argentina and Massachusetts. I have never failed to obtain acceptance for my work as installed and in all that time I have only had to resort to two formal appeals both of which were resolved in my favor. I have worked on projects as large as steam turbine generating stations and as small as stand alone photo voltaic radio relay stations. I know power and lighting wiring fairly well and I know for a fact that the absence of an effective fault clearing pathway will lead to equipment damage, fires of electrical origin, electrical injuries, and electrocutions. -- Tom H
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I see you have covered the Grounding Systems part of the NEC clearly in your last post.I believe the Neutral is a Non Earth ground fault path for current., and that other than in an Impedance Grounded Neutral System the Neutral Conductor shall not be grounded except through the Neutral Grounding Impedance.250.186(C)
Can you be Specific as to How Mr. Tarin go about Grounding the Panel in his Cabin. I'm sure he'd like to get it underway.
Roy
PS: Be it known I have the utmost respect for Firefighters, living in NYC tenements they have more than proved their expertise and great concern for saving lives., having been trained by several of them as a C.E.R.T. I am aware mostly of what I can & cannot do....Most Noticeably: I do not see why you object to the Inspectors, my or the others take on this Grounding Issue.
if you still care: Why do you think the Neutral & EGC should Both be grounded at the Panel in the Cabin ? if he was to ground them Both, how much distance should the seperate electrodes have from one another.
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Roy Q.T. wrote:

As has been stated several times already: At the cabin panel, bond the neutral and grounding-conductors together (same as a "main bonding jumper"). This is done to provide a low resistance for hot-to-grounding conductor shorts; low resistance = high current; high current = circuit breaker trip. Connect the panel ground-neutral to a "grounding electrode" (with a "grounding electrode conductor"). Connecting the panel ground to earth keeps grounding-conductors at the earth potential at the cabin. Connecting the neutral to ground keeps the system ground-referenced (and provides a path for lightning). (A ground rod is commonly used for a "grounding electrode" but it is probably the worst.) There are not separate electrodes.
> I do not see why you object to the Inspectors, my or the others take on > this Grounding Issue.
250-94 is logically the same circumstance as the pole service and remote cabin. Bonding the neutral and grounding-conductors at the cabin will give a lower resistance fault path to trip a circuit breaker. A grounding-conductor from the pole will add the resistance of that conductor (at 300 ft if I remember in the dim past of the original post). It will also add 2 connections, one at the more weather exposed outside meter. I really don't remember the 'other' method for 'earthing' the cabin panel, but the panel/grouinding-conductors must be connected to a grounding-electrode so the grounding-conductors are at the earth potential at the cabin. If there are more than one grounding-electrodes they must be bonded together.
Bud--
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Roy Q.T. wrote:

Roy Maybe it will help you understand were I'm coming from if you do the calculation of the voltage between the Equipment Grounding Conductors (EGCs) in the cabin and the earth in the event of a fault between the ungrounded current carrying conductor (hot) and one of the EGCs in the cabin. The reason it is common practice to install two ground rods is that unless the first rod has a resistance to ground of 25 ohms or less a second rod is required. Since the equipment used to measure resistance to ground is expensive and, in some cases time consuming to set up, most electricians just drive the second rod. It is very commonly true that even with two rods the resistance to ground is 50 to 100 ohms. Since the power company's multi grounded neutral is tied to ground at every transformer and at every single service disconnecting means we will assume that the resistance to ground at the transformer is effectively zero. So relative to the earth the transformer's secondary produces a voltage of 120 to ground. When that current faults to an electrode system that is not effectively bonded to the utility's Multi Grounded Neutral (MGN) the entire 120 volts is across the grounding electrode system. Since you are an electronic technician you can do the calculation in your sleep. Since V=I*R V/R=I. The voltage of 120 divided by the best case grounding electrode resistance of 25 ohms equals 4.8 amperes of current flow. The smallest Over Current Protective Device (OCPD) used in North American Practice is fifteen amperes. The impedance to ground of the isolated grounding electrode system is two high to trip the breaker and clear the fault. As long as the fault continues to exist there would be a 120 volt potential between the entire Equipment Grounding Conductor network and the earth itself. So Mr Tarin plugs in his weed-whacker, drill, or electric mower and tries to do some work either outside or while in contact with a naturally grounded surface. If the tenth of an ampere that it takes to cause ventricular fibrillation flows through his body he dies.
So instead of the isolated grounding electrode system we bond it to the grounded current carrying conductor that most of us call the neutral. The resistance of the fault clearing path now drops to less than an ohm. 120/10 so the OCPD opens the moment a fault occurs thus clearing the fault and provoking the occupants to repair the defect or have it repaired. By adopting this second strategy we comply with the US NEC language in 250.4 (A) (3), (4), & (5).
250.4 General Requirements for Grounding and Bonding. (A) Grounded Systems. ... (3) Bonding of Electrical Equipment. Noncurrent-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path. (4) Bonding of Electrically Conductive Materials and Other Equipment. Electrically conductive materials that are likely to become energized shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path. (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 not be used as the sole equipment grounding conductor or effective ground-fault current path.
In a three wire feeder situation the neutral is the only conductor that meets the requirements for a "permanent, low-impedance circuit capable of safely carrying the maximum ground-fault current likely to be imposed on it." -- Tom Horne
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You should always use a totally separate earth grounding system on a sub-mains supply. A separated out-building should always have its own local earth fault conductor, and should never rely on the transfer of an earth fault loop directly from the supply source. The wiring for the sub-mains supply to the out-building should be protected by the main earth, but once at the out-building the distribution apparatus should have also have its own local earth grounding spike installed, and a heavy gauge conductor connected between the distribution panel and the spike of course.
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