Ok troubleshooting wizards

[George Stolz]

Boss and I figured it would be cheaper to install the blocker than for us to keep tracing this problem. Will let you know how it works, prolly be a week or two before it comes in though.

How much is it?

 

[ramsy]

Is there a way to test that svc.neutral yourself?

1) With open disconnect does shorting a lifted svc.neutral, with a solenoid meter (Wiggy), show current? This would be evidence against the Poco, since the water is not in this path.

If not..

2) With open disconnect, does shorting a lifted svc.neutral, with a Hz meter show neutral harmonics? Are similar frequencies found on the bonding grid? More evidence against the Poco, especially if xfrm's transmitting harmonics from elsewhere in the grid, and evidence of galvanic corrosion exists at the aluminum ramp, as winni & I mentioned earlier.

ShureTest manuals describe harmonics as one source for ~1.9vac. Ideal's 61-165 manual states,

"In a 3-phase circuit with a shared neutral, a high (> 2vac) ground-neutral voltage could indicate (among other things) ..harmonic distortion on the shared neutral."

If none of the above exists..

3) With open disconnect, does shorting a lifted svc.neutral, with a high-Z digital volt meter (DVM) show voltage? Since, the water is not in this path this may provide evidence of a service neutral bringing capacitive inductance to the bonding grid and ramp, perhaps from sharing close proximity with energized conductors upstream?

 

[Smart $]

A ground rod directly energized by 120 VAC cannot bring the earth to an equal potential immediately surrounding it.

Circuit must be on an FPE breaker

A ground rod driven in the shore 30' away from the ramp has no hope of bringing the potential of the water up to the potential of the ramp.

The idea isn't to bring the water up to the potential of the ramp (which in fact is impossible), but rather the potential of the ramp down (or a lot, lot closer) to the water. Don't forget that the water is saturating the ground along the shoreline (that is, as long as the shoreline isn't a cliff). In the picture you attached, saturate the soil around the ground rod with water. How will this change the voltage readings? By comparison, they will all decrease proportionally to the decrease in resistance to, shall we call it "mother earth". What the decreased resistance is depends on a lot of factors and how well the water saturated the area. If saturated to the degree it reaches the local water table, the decrease in resistance will be substantial. Terra firma consists of many different components in various mixes. Most of them are NOT good conductors. Add water to the mix and you're in a whole different ball park!!!

As long as the ramp has potential, there will be a difference between the ramp and the water.

The point is to eliminate the potential of the ramp.

Right about now, you're probably thinking I'm missing the point; that the ground rod is a good path to ground and can easily dissipate a mere 1.9 volts. But to say that is to forget that electricity is seeking any path to it's source, not just the one we'd most desire.

Seeking not just any path, but the path of least resistance. And we can control that!

As to being code compliant by putting a ground rod by the dock and bonding it to the EGC, see 250.54...

 

[iwire]

Circuit must be on an FPE breaker

Joke?

FPE, GE or Square D it does not matter a ground rod will not trip them.

The idea isn't to bring the water up to the potential of the ramp (which in fact is impossible), but rather the potential of the ramp down (or a lot, lot closer) to the water.

And a ground rod can not do that either.

Seeking not just any path, but the path of least resistance. And we can control that!

No we can not 'control that' electricity will always use all paths.

Saying 'electricity takes the path of least resistance' is only part of the story.

It will take the path of least resistance and at the same time every path that is not of infinite resistance.

 

[e57]

Good point on 250.54.... But in this context of wording is permissive, 250.32 seperate structures is required. (shall be connected) But would save some install costs if the ramp were "equipment".

250.54 Supplementary Grounding Electrodes.
Supplementary grounding electrodes shall be permitted to be connected to the equipment grounding conductors specified in 250.118 and shall not be required to comply with the electrode bonding requirements of 250.50 or 250.53(C) or the resistance requirements of 250.56, but the earth shall not be used as the sole equipment grounding conductor.


Commentary: Grounding electrodes, such as ground rods, that are connected to equipment are not permitted to be used in lieu of the equipment grounding conductor, but they may be used for supplementary protection. For example, grounding electrodes may be used for lightning protection or to equalize potentials in the area of the equipment. Sections 250.4(A)(5) and 250.4(B)(4) also specify that the earth not be used as the sole equipment grounding conductor or effective (ground) fault current path.

 

[iwire]

Mark this is what it says.

to equalize potentials in the area of the equipment

But it really can not do that.

The only place that will be 'equalized' is right beside the ground rod.

Take a step away from the rod and the difference of potential is still there.

 

[iwire]

Check out this by Mike Holt.

To understand how a ground rod is useless in reducing touch voltage to a safe level, we need to know (1) what touch voltage is, (2) at what level touch voltage is hazardous, and (3) how earth surface voltage gradients operate.

1. Touch Voltage - The IEEE definition of touch voltage is ?the potential (voltage) difference between a grounded metallic structure and a point on the earth 3 feet from the structure.?

2. Hazardous Level - NFPA 70E - Standard for Electrical Safety Requirements for Employee Workplaces, cautions that death and/or severe electric shock can occur whenever the touch voltage exceeds 30V.

3. Surface Voltage Gradients - According to IEEE Green Book Std 142 [4.1.1], the resistance of the soil outward from a ground rod is equal to the sum of the series resistances of the earth shells. The shell nearest the rod has the highest resistance and each successive shell has progressively larger areas and progressively lower resistances. This following Table lists the % of total resistance (%R) and the Touch Voltage (T-V) based on a 120V fault. The table?s % of resistance is based on 25 feet representing 100% of the total earth resistance for a 10-foot ground rod having a diameter of 5/8 inches.

Distance from Rod %R T-V1 Foot (Shells 1)1 foot 68% 82V3 Feet (Shells 1-2)3 feet 75% 90V5 Feet (Shells 1-3)5 feet 86 % 103V
With the intention of providing a safer installation, some, if not most, in the electrical industry think a ground rod can be used to reduce touch voltage. However, the voltage gradient of the earth drops off so rapidly, a person in contact with an energized object (at any building wiring voltage) can receive a lethal electric shock.

You can see the whole page here

Girl Killed

 

[don_resqcapt19]

Smart $,

At the shoreline? I would think that a ground rod or rods at the shoreline would have a lot lower impedance to ground than those that are a good distance away...

The impedance doesn't matter as long as it is somewhat homogenous in the area of the rod(s). The percentage of the total impedance of the rod at 3' is ~57% no matter what the total impedance is, and therefore the voltage drop is the same. Yes, there will be some small decrease in the voltage drop along the multigrounded neutral system every time that you connect a grounding electrode to the system, but this will be so small as to be unmeasurable.


Don

 

[don_resqcapt19]

Right about now, you're probably thinking I'm missing the point; that the ground rod is a good path to ground and can easily dissipate a mere 1.9 volts.

Ground rods can't dissipate voltage. The only time this can happen is where the impedance is low enough to trip the OCPD that protects the faulted circuit. The ground rod just becomes a load and that does not change the voltage that is being supplied to the rod.
Don

 

[gobblerhuntr]

How much is it?

I think retail is $940 ish. But I got a discount being a POCO and the total was about $600.

 

[George Stolz]

A ground rod directly energized by 120 VAC cannot bring the earth to an equal potential immediately surrounding it.

Circuit must be on an FPE breaker

Bob's statement is for the most part correct. Consider a ground rod at a low resistance of 25 ohms. Applying Ohm's Law, at 120V that 25 ohm ground rod will be a load of 4.8 amps. This will not cause a circuit breaker to trip.

Seeking not just any path, but the path of least resistance. And we can control that!

If that were true, then if you were to install 1 can with a 65W lamp on one switchleg, and another switch supplying 10 cans on another leg, then the switchleg supplying the 1 lonely can would be dead. That lamp would not light, because the path of least resistance for that circuit would be through the 10 cans.

"The path of least resistance" is a common misunderstanding. Electricity seeks any path back to it's source.

That is why we're having this discussion in the first place; There is no such thing as a 1.9 VAC power source. This voltage is coming from a 120V or 277V (or an outside chance of 7200V) source. Since that power is seeking any path to it's source, then a small fraction of it is finding it's way out onto Lou's ramp.

 

[hardworkingstiff]

George,

Are you really 4 years into this trade?

BTW, I called the PoCo rep and he said they have not had a chance to test their cable yet. He also reminded me that if the cable tests OK, it was our problem because all of their stuff is grounded properly.

 

[hillbilly]

Steve,

I don't agree. The utility ties the primary and secondary neutrals together. Voltage to earth from the neutral with the service disconnect off is a measurement of the voltage drop on the utility primary and secondary neutral.
Don

I totally agree with you Don.
I know that there is potential at the very end of the (grounded) and grounding conductors, at the very end of the ramp, as far away from the service panel as the circuit reaches. As long they are bonded to the service neutral at any point, they will have potential to earth. This potential will drop as the distance increases and finally reach a point so low that it won't be discernible by any method known to man, but it will still be there. As long as there is enough pressure (voltage) to push even one electron (or proton), the grounded conductor will have potential to earth.

That's why his grounding conductor (and bonded ramp) have 1.9V potential to earth.
It can't be eliminated, but it can be reduced to a point to where it's not noticeable.
IMHO, One ground rod driven and bonded may not do the job, but it will have some efffect. Any effort that reduces the potential of the grounding conductor to earth will have a remedial effect.
Sorry for the long post, but this is a interesting subject and I'm on a learning curve.

steve

 

[Smart $]

Circuit must be on an FPE breaker

Bob's statement is for the most part correct. Consider a ground rod at a low resistance of 25 ohms. Applying Ohm's Law, at 120V that 25 ohm ground rod will be a load of 4.8 amps. This will not cause a circuit breaker to trip...

First off, for Bob's sake, yes it was a joke!

Second, a ground rod at a resistance to earth of 25 ohms is a high resistance. So high it is actually the max permitted by code without augmentation.

Additionally, I'm well aware of what you ask me to consider, George. Bob's statement is only correct in the context of an assumed typical situation. However, it is not all encompassing. Your example makes the same assumption. Both of you are probably assuming a breaker trip rating of 15 amps or higher... again, this is a typical situation, but not all encompassing. In some of the industrial situations I have been involved with, I have encountered CB's having a trip rating of less than 1 amp. If the circuit in the image was on that breaker, it most likely would have tripped. In summary, Bob's statement is a vague assertion at best. He later provides reference material, but even that uses a typical situation.

...

Seeking not just any path, but the path of least resistance...

If that were true, then if you were to install 1 can with a 65W lamp on one switchleg, and another switch supplying 10 cans on another leg, then the switchleg supplying the 1 lonely can would be dead. That lamp would not light, because the path of least resistance for that circuit would be through the 10 cans.

"The path of least resistance" is a common misunderstanding. Electricity seeks any path back to it's source....

The misconception is on the part of the reader, extracting more information than what was stated. Let me clarify. I said electricity "seeks" the path of least resistance. I did not say electricity does not utilize all available paths. Reworded to express something closer to my original intent: Electricity seeks the path of least resistance but utilizes all available paths inversely proportional to the resistances encountered in achieving or in its attempt to achieve neutralization.

...That is why we're having this discussion in the first place; There is no such thing as a 1.9 VAC power source. This voltage is coming from a 120V or 277V (or an outside chance of 7200V) source. Since that power is seeking any path to it's source, then a small fraction of it is finding it's way out onto Lou's ramp.

I am in complete agreement here.

Getting back to the issue, it seems most are of the assumption/impression/conviction (that should cover it ) that if a ground rod was to be driven at the shoreline by the dock, it will have grounding properties the same as a typical situation. I don't believe this will be the case. In testing ground rod resistance. the American Electricians' Handbook says when driving test rods is impractical, such as when the entire area is paved street and concrete sidewalks, "In such a case a fire hydrant can be used for the auxiliary ground, or a pad made of several thicknesses of heavy cloth about 1 ft (0.3 m) square and saturated with saltwater can be placed on the sidewalk. (Fig. 8.129)" Why the saltwater? (rhetorical question) I recall the Intercoastal Waterway, or something of the sort, being mentioned. Does that not mean saltwater body? I'm definitely of that impression it is a saltwater body. I belive this condition alone will change the characteristics of a ground rod.

The biggest question I have in this discussion is: How much current is available behind that 1.9V differential? A simple test would be to connect a bare copper wire to the EGC at the ramp and, while monitoring current on this wire, toss the loose end in the water. Perhaps a switch should be inserted Also wondering if there is any current being "drained" at the main?

Anyway, with some of the persuasion a grounding electrode at the dock is required, all I can do is wait to see how it plays out...

 

[George Stolz]

First off, for Bob's sake, yes it was a joke!

I'd be careful about posting jokes without making that clear, as it only contributes to people's misunderstanding of grounding and bonding.

Second, a ground rod at a resistance to earth of 25 ohms is a high resistance.

No, it's not. It's not unheard of to have a ground rod at as much as ten times that resistance to ground or more.

So high it is actually the max permitted by code without augmentation.

You assume that the CMP's reasoning behind the requirement is that they consider that value to be "high." That remains to be seen. I have not seen any evidence one way or another regarding their reasoning behind the requirement.

Both of you are probably assuming a breaker trip rating of 15 amps or higher... again, this is a typical situation, but not all encompassing. In some of the industrial situations I have been involved with, I have encountered CB's having a trip rating of less than 1 amp.

That is irrelevant - the earth is never an acceptable ground fault current path.

If the circuit in the image was on that breaker, it most likely would have tripped.

It would have tripped when the ballast of that pole was energized, regardless of a fault condition.

The misconception is on the part of the reader, extracting more information than what was stated. Let me clarify. I said electricity "seeks" the path of least resistance.

I read what you wrote. Writing it a second time doesn't make it any more correct, and you are doing a disservice to the apprentices and students who visit this forum for accurate information. It is a falsehood. It is incorrect. It is misleading. It doesn't merit defense; the statement only serves to confuse and misinform.

I did not say electricity does not utilize all available paths.

That is a profound omission!

Let's change your "correct comment" to be fully correct: Electricity...utilizes all available paths inversely proportional to the resistances encountered in achieving or attempting to return to it's source.

Look, I agree that driving a ground rod might (probably will) help with the problem at hand. I agree, that the resistance of the ground rod will likely be less than 25 ohms when driven into this shoreline. Given this second parallel path (the first being the person touching the ramp and the water simultaneously), then the majority of current will flow into the grounding electrode.

• Venturing a wild unsubstantiated guess, I would say that Lou had a resistance of 250 ohms when he touched the water with a cut on his finger.
• Venturing a second WAG, I'd say that if a ground rod were driven into the salty shoreline, it would have a resistance of 5 ohms.
• Given that WAG ratio, it should direct 50 times the current through the ground rod that simultaneously travels through the person.

I have no idea what voltage readings that would produce, or if the tangible shock would disappear entirely. I do know I'd feel better:

• Installing the blocker (if it didn't cost an arm and a leg)
• Discovering the damaged neutral causing the voltage (time consuming and who knows if you'll find it)
• Installing entirely nonmetallic equipment and raceways on the dock, and rhinolining the existing ramp or replacing it with wood or fiberglass. (Expensive, time consuming, and extreme, considering the non-lethal nuisance nature of the voltage)

So, I guess the rod is the answer after all. But it's not very comforting, IMO.

And Steve thought he had a long post! Sorry about that!

Edits to keep adding to my already overly long tirade...

 

[don_resqcapt19]

Steve,

It can't be eliminated, but it can be reduced to a point to where it's not noticeable.
IMHO, One ground rod driven and bonded may not do the job, but it will have some efffect.

Yes it will have some effect, but only within a few feet of each grounding electrode. Given the impedance of all of the paths for the grounded conductor current to flow on, the addition of additional paths will not reduce the voltage drop by any measurable amount. The voltage will still be there.
Don

 

[e57]

Check out this by Mike Holt.

You can see the whole page here

Girl Killed

Bob, apparently there was some disagreement with Mike Holt on the topic, I might be one of them.... It also sounds as though the voltages in the incidents were far greater than what were are talking about in this situation? Possibly an ungrounded conductor fault. This one I think we are all pretty sure is a voltage difference from a grounded conductor.

I am glad you posted it though! As it makes some good examples of grounding shells etc. Which is a contributor to the problem at hand, the distance to the other electrodes...

Although I may or may not have made myself clear, I dont think a rod would eliminate this volage of 1.9 volt completley, it certainly would help IMO. Its also clear that its required by 250.32. As there is more than one circuit at this structure...

If we take M.Holts example and modify it for this 1.9 volts it would look simular to this.... (which is not exact due to not knowing the soil make-up...)

Distance from Rod %R T-V
1 Foot (Shells 1)1 foot 68% 1.292V
3 Feet (Shells 1-2)3 feet 75% 1.425V
5 Feet (Shells 1-3)5 feet 86 % 1.634V

Two rods would further reduce this... Like I said before, closer to the same...

Another way this could be further reduced IMO would be to put an isolation transformer as close as possible to the ramp, and would still require a rod or two there. To keep its gounding and grounded conductor to earth low... It would be much lower than any tranny further away IMO.

Another idea would be to re-make this ramp out of something non-conductive, and PVC conduit, but that would still leave this voltage on the GEC and also the exterior or any case grounded equipment. Still a hazard....

hardworkingstiff, I bet you wish you took that office job now huh?

Man you picked a winner here....

 

[don_resqcapt19]

Two rods would further reduce this... Like I said before, closer to the same...

Only within the sphere of influnce of the rods...as soon as you get over 5' from any of the rods you have 86% of the original voltage.
Don

 

[e57]

Isn't 86% closer? And required by 250.32?

 

[Smart $]

I'd be careful about posting jokes without making that clear, as it only contributes to people's misunderstanding of grounding and bonding.

YES, SIR! SORRY, SIR! IT WON"T HAPPEN AGAIN, SIR! [size=-2](not)[/size]

"Second, a ground rod at a resistance to earth of 25 ohms is a high resistance."

No, it's not. It's not unheard of to have a ground rod at as much as ten times that resistance to ground or more.

"So high it is actually the max permitted by code without augmentation."

You assume that the CMP's reasoning behind the requirement is that they consider that value to be "high." That remains to be seen. I have not seen any evidence one way or another regarding their reasoning behind the requirement.

I was speaking [writing] in terms of functionality as implied by code. You are correct in that a ground round may have a resistance many times the implied target value... and as I stated, code requires when this is the case with a sole [system?] electrode, it must be augmented. (Is there an echo in here?) You say ta-may-toe, I say tuh-mah-toe...

"Both of you are probably assuming a breaker trip rating of 15 amps or higher... again, this is a typical situation, but not all encompassing. In some of the industrial situations I have been involved with, I have encountered CB's having a trip rating of less than 1 amp."

That is irrelevant - the earth is never an acceptable ground fault current path.

That's exactly right. As I see it, the installation as depicted is in violation by not being bonded to service ground!!!

If the circuit in the image was on that breaker, it most likely would have tripped.

It would have tripped when the ballast of that pole was energized, regardless of a fault condition.

The remark was only to offer contention to Bob's assertion, "FPE, GE or Square D it does not matter a ground rod will not trip them [circuit breakers]." Nothing more. I tend to interpret in "many shades of gray". IMO, you guys are little too "black and white".

...and you continue to make assumptions. In all likelihood, you are correct in there being an HID ballast connected atop the pictured pole. Nevertheless, it is an assumption. Since you assume the load is an HID ballast, I'm going to assume it is a low current sensor of some sort, for the L of it Regardless, the one thing I want to make plainly evident here is: Assumptions in this profession can get you killed!

"The misconception is on the part of the reader, extracting more information than what was stated. Let me clarify. I said electricity 'seeks' the path of least resistance."

I read what you wrote. Writing it a second time doesn't make it any more correct, and you are doing a disservice to the apprentices and students who visit this forum for accurate information. It is a falsehood. It is incorrect. It is misleading. It doesn't merit defense; the statement only serves to confuse and misinform.

"I did not say electricity does not utilize all available paths."

That is a profound omission!

Again, that is exactly correct. I'm a profound person and I can not, will not change my disposition to suite your's or anyone's desires or requirements. In the interest mutual respect, I will attempt to "bend" a bit, but that's the best I can offer. Nonetheless, you need to be aware I'm not going to rewrite "the book" for every comment I make.

Let's change your "correct comment" to be fully correct: Electricity...utilizes all available paths inversely proportional to the resistances encountered in achieving or attempting to return to it's source.

You can change my words any way you want if it makes you feel better. Do you feel better now?

So, I guess the rod is the answer after all. But it's not very comforting, IMO.

I forgot to mention that I am among those of the contention a ground rod is required.

FWIW, I've been on hiatus from citing code longer than you've been in the trade. On that note...

Grounding conductors are intended to have zero current---oh, oh, let me correct that---no objectionable current. As I suggested, a simple test will provide the answer. If in all likelihood, objectionable current will result, so enlighten yourselves with with 250.6(A, B)... but then I have to ask how is it possible to meet the requirements of 250.4(A)(5) or (B)(4) in persuing alteration 250.6(B)(3)?