Is body of water considered ground?

The floating dwelling units have to ground their system. How about a dwelling unit that is built on a permanently constructed deck that is on the body of water?

How is grounding achieved?

Wave mechanics?

The ocean would be considered the perfect ground plane.

The actual electrode would have to be non-corrosive in salt water.

Titanium and Gold...

?

How do you attach to the water? How do you install an electrode?

On the comical side, this would be a true floating ground.

Does the NEC even apply?

FRom the comment of a 'dwelling unit built on a permanent deck, I would say...yes.

I gave the OP a lot of thought, as to a excersize in humor, or a serious question....& I'm still not sure.

It is a serious/curious question.



How would one install a grounding electrode?

Stainless steel pontoons?

I have dealt with a few floating facilities. Answer me this, is the house affixed to the shore and is hired wired from the shore? If so then the grounding is achieved at the main on shore. See NEC 553 for more details.

If it's mobile, then it falls under different rules. NEC may or may not apply. I might be able to assist you with that

Think about the way Ships, Aircraft, or even a Space Station is "Grounded".

What would be referred to as "Ground" in these cases.
(hint: think "Automobile's Ground")

-- Scott

How do you construct a deck permanently?

Is it on pilings? If it is wooden pilings, I don't know the "proper" way to ground. If they are steel reinforced concrete pilings, wouldn't it be the same as a foundation?

Sparky summed it up. Floating buildings are covered in 553.

It is interesting that I don't see anything particular about the grounding for a building built on a pier beyond Article 555 and that does not talk much about service equipment. Personally I would want to the the service disconnect up on the shore and a feeder with the EGC meeting the requirements of 555.15 (basically an insulated wire).
I see nothing that relieves the installer from following 250 part III when it comes to the electrode and nowhere in there does it allow a connection to the water to be a ground electrode.

In a "boat" with no shore connection, a bronze grounding plate in the hull is common.

As usual, we have at least two separate issues. Let's identify them, and maybe the question will answer itself.

The first is the iisu of clearing faults. This requires a low-impedance path back to the PoCo transformer, and the "ground rod" has no role. Often the neutral is this path.

Then there is the variation: a fault from a 'hot' wire to a metal case. That's where we need a good path between the fault and the PoCo neutral, and this is what we use the green wire for. IMO, "stray current" issues arise most often because this path is inadequate.

The "other" grounding has to do with lightning and static electricity. Those are the only forms of electricity that want to return to planet earth. Perhaps at some point boats with non-conductive hulls will be required to 'bond to water' much as we now require pools.

If a boat is not receiving power from shore, there is no reason for there to be any electrical bond with shore. In that instance, there needs to be a low impedance path back to wherever the electricity was created.

Now we enter the paradox of having multiple power sources. That is, should there be a failure of the PoCo neutral, then we have just energized the entire marina. Since fresh water isn't such a great conductor, we WILL have voltage gradients severe enough to kill. Your ONLY protection in this instance comes from GFI's.

The way I see it, you have to answer two questions to answer.

1) Is it floating?

2) Is it permantly connected to shore power?


If the "permanently constructed deck" is floating, AND not permanently connected to shore power, it is a boat.

If the "permanently constructed deck" is floating, AND permanently connected to shore power, it is a structure that must follow the NEC.

If the "permanently constructed deck" is NOT floating, AND not permanently connected to shore power, it is a stand alone system.

If the "permanently constructed deck" is NOT floating, AND permanently connected to shore power, it is a structure that must follow the NEC.

i am not working on a floating building or a deck.
We have some floating buildings about an hour north of where i am so a thought popped in my head as to how their grounding electrode system is done.

I never knew that there is a section in the NEC that applies to that.



Thank you all for your replies.

To answer the OP and to prevent confusion about grounding, the ocean is not an acceptable grounding point as far as the NEC is concern. On float houses, houses on piles, boat houses, any structure which are "permanently" attached to the shore falls under the local electrical code.

In regards to the OP and clarify some of the following posts, the grounding electrode system (i.e. Rods, pipes, plates, rings, etc.) have nothing to a structure's internal wiring or our trade calls, equipment grounding conductors. They both do totally separate things. The simplest way of putting it is the grounding electrode system protects a structure from external sources like near by lightening strikes and faults in the distribution system like a faulty transformer or downed primary on a secondary line. The equipment grounding protects the same structure from internal faults like ground faults. With that said, let the public lashing commence but in a new post

I think most of us know the difference between EGC and GEC.

But why isn't the water an acceptable grounding point that may serve in place of the earth.

on a second note, I think the water would be a great conductor specially salty water. Am i wrong?

i guess my basic question is Can body of water be considered earth?

Salt water is an excellent conductor but NFPA has never recognized it in part III of 250 so we are left with terrestrial ground electrodes.

Clarification time.
My comment on pg 1 was to Larry; "YES" the NEC does apply; it was not a 'yes' to water being acceptable as a 'ground'.

That said, I apologize for the above; workplace confusion and to much multi-tasking!

ET popped right into my head on that jem Greg.....


~S~

Seattle uses Article 553 and requires a connection to the EGC at the Service point that ends up being the 'shore power' for their floating houses...if that helps with another answer for the question.

http://www.seattle.gov/dpd/static/2008%20SEC%20replacement%20pages_LatestReleased_DPDP017554.pdf

The open question is still a building built out on the end of a pier. There is nothing I see that prevents you from having the service equipment on the pier but it looks like you still need the ground electrode back on the shore. For that matter even if this is a 250.32 building, fed from a service on the shore, the required ground electrode at the building will be back on shore or a made electrode on the bottom.
"I ain't inspecting that one in the winter"

ok, a made elctrode.... , like what? an anchor? ~S~

An anchor?
Sure, as long as it is buried 30" below the bottom, 2 sq/ft of area, 1/4" or greater thick and connected with a 250.66 conductor

Greg, to answer your question, Fixed buildings on piers fall under article 555. 555 does not address anything specific service grounding. The service is required on shore are identified on floating docks and marinas. The options I can think is either put the service on shore and ground it there, run just the ground back to shore or work with the AHJ and round the ground down the bottom of the water. The latter may require additional approval form jurisdictions. I would imagine typically the jurisdiction stops at the beginning of the pier. It would be a case by case basis with the local AHJ

In general, water is not considered conductive because its not in its purest form. Its the impurities in the water that makes it conductive. I would imagine the chemical composition of the water varies greatly form one moment to the next as the water moves around. Here where I am at, the water can be salty the a few hours later, its fresh water.

In a side note, earlier in this string, I spelled out the difference between the GES and the EGC systems. My intent was only because both systems were talked about in this string. In my personal experience, these two subjects are all too often misunderstood and have confused even good electricians, IMOP, its one of the most important subjects to understand in the trade. Although many of us understand the topic, some don't and with both of them were mentioned, I felt it should be touched on.

Grounding and bonding is just a pet peeve of mine.

I bet most AHJs are going to want to see a service disconnect up on shore with a ground electrode system there for a building on a pier. I am still not sure how the reconcile 250.32(A)
It would be very easy to argue article 555 does not apply if there are no docking facilities on this pier.
I will ask the boys over on Florida IAEI since buildings on piers are pretty common here. I just never had to do one myself.

The more I think about this the more I think I would call the whole pier the "building". The service disconnect would be at the nearest point of entry, the foot of the pier (beach side) and you would connect the ground electrode system there.
Everything else is just a feeder or a branch circuit.

That would be my guess with the AHJ. The dock itself would likely fall under the of the water its built over like the Army Corps of Engineers, the house itself would likely fall under the local applicable building and electrical codes.

I don't think that 250.32(A) would apply here. I would contend that in this scenario, 250.32(D) would apply. If the service at the foot of the dock on the shore and the house were under the single "management", the the GES at the meter would all you need provided an equipment grounding conductor was ran with the feeders out to the house.

well it's the whole theory part of it Sparks, but 250 never really spells it out

as we know, one of the chief GES reasons to exist is supposedly to give lightning a place to go.

so shorter and more direct routes would be appropos

in fact, i've heard it argued that a GEC would be better tied to the noodle at the weatherhead of a service, rather than meter or panel (poco preferenced)

so while i can imagine the AHJ being ok with a shore service GES, and a fat EGC run out to the end of a pier with the feeder & maybe 'bond' the water like pools do now with metal ladders , i can't see the theory end of it being 100% without hiring Lloyd Bridges....

~S~

Update from Fl IAEI
Bryan Holland (City of North Port) suggests the rebar in concrete pilings would be a good ground. He also says the shore side disconnect should happen.

Greg:
I agree with Bryan (BPHGravity, I believe) with the rebar in the concrete pilings, if & when that construction is available. The structures we have on piers here are wooden pilings; the grounding of the services is made on 'shore' (terra firma), at the disconnect, with a GEC installed with the feeder to the structure.

I agree with the concrete piles (vertical ufer) in principle but may requires an engineer approval. A lot would have to do with how deep the piles are and the muck its buried in

Greg,

I know this might be a little off the topic, but Talking about the Grounding Electrode being encased in concrete that is used for services in new houses. I hear from people that the electrode might blow out a footing if it was to take a direct hit from a lightning strike. Now being that you are in the lightning state, have you or any friends ever seen or heard of an instance where lightning damaged a footing or electrode?

I have never actually heard of that happening. I bet the only way it could would be if the concrete itself was very dry and not particularly well grounded itself. Heat comes from high resistance. P=I2R

Actually I suspect the opposite. The damper the concrete, the lower the resistance. Lower resistance means more current. More current PLUS water means a greater chance of forming steam. More steam, greater probability of catastrophic failure.

Larry C

All of the current from a lightning strike is going to be there no matter what (it came through 5-10 miles of air). If you are jamming it through a high resistance you get a lot of heat. If it goes through a very low resistance path it dumps the energy into the ground.
If you look at the extremes you can look at an old dried out tree, that will literally explode or you can look at the copper conductors from an air terminal that shows no damage at all.

All that said, I have never heard of a properly made Ufer blowing up and we have a lot of lightning strikes here.

It's not uncommon to see such trees hiking or hunting either, some looking like they were split by a giant axe

yet there were those who had to deal with Mother Nature before the modern age of our trade

for instance, some of the bigger barns built had a beech ridge runner , and you may have seen some ash trees nearby

it was believed that beech repelled, and ash attracted lightning

~S~

I don't have alot of experience with lightning. I have been wrong many times in the past and I will be wrong in the future. I still think that it would be possible to have catastrophic failure in a concrete enclosed electrode, but I know of no cases were it has happened.

Lets submit it to Mythbusters.

When mythbusters did their lightning show they couldn't get any bad things to happen until they lifted the ground electrode conductor. When they had the whole house, and phone line, isolated, all sorts of bad things happened.
We had a lot of lightning experience in the computer biz and the real answer was always more grounding and bonding.

I like that idea, Larry.
They've got access to a great lightning facility.
They already did a show about being on the phone or in the shower during a lightning storm.
You should send it in...they're probably always in need of neat ideas for the show.

IMHO, you should note the raw data rather than trusting any of their "scientific conclusions".
Remember their show that proved that bullets fired straight up wouldn't fall back down and kill you?
They ran their tests underneath bulletproof shields...and interviewed a Doctor who had issued more than 1 Death Certificate for just that case.
Yet they had no problem saying that it was impossible.

Let the buyer (and viewer) beware.

In defense of the bullet story, the people who were killed by bullets shot in the air were pretty far away from the shooter so they were not shot "straight up".