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doc,

it is apparent one of the boats is not grounded. when the coax fried , one of the boats was using that wire to "seek ground".

Please get some expert help! the following is very long and taken of MIKE HOLTS site and as DR. BOB said will show you the problems you are facing. None is the right answer for you doing this yourself and I'm not giving you advice to do any of this yourself. Please listen before you do harm.
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I have a 1985 house boat with aluminum hull. When I installed a generator 2 years ago, the code called for isolating the hull from ground. I understand the 2003 NEC now calls for grounding the hull through shore power cord to the power post. I am not an electrical engineer, but I am a mechanical engineer with industrial machinery experience. Grounding the hull seems wrong to me as it's a sure way to cause a voltage between the hull and the water, thereby being a safety problem for swimmers boarding the boat, as well as cause electolosis problems in the hull material.
Can you tell me reasons for changing the code to include grounding the hull? Are there any safety problems with not grounding the hull?
Thanks!
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don_resqcapt19
Moderator
Member # 4

posted June 09, 2003 10:58 AM
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First, there is no 2003 NEC. The current edition is 2002 and the next one will be 2005. Second the NEC does not apply to boats.

quote:
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90.2(B) Not Covered. This Code does not cover the following:
(1) Installations in ships, watercraft other than floating buildings, railway rolling stock, aircraft, or automotive vehicles other than mobile homes and recreational vehicles
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Don
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liebler
Member
Member # 5458

posted June 09, 2003 07:23 PM
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House boat manufacturers tell me they are tearing out their hair because the Coast Guard is requiring them to follow NEC 2003, Article 250, related to grounding.
I called the Coast Guard, who refered me to NFPA 70, which is the NEC, and told me to use the 2003 version.
I'll try going back to the Coast Guard on the question. Any further advice you could provide would be appreciated.
Thanks!
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dereckbc

Moderator
Member # 30

posted June 09, 2003 07:39 PM
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There is no 2003 NEC. However grounding the generator to the hull would not induce a voltage between the hull and water. Not sure about electrolosis as this is usually associated with DC and not AC.

As Don has stated the NEC does not cover boats. But it does cover Marinas in article 555. And if you are supplying power from the Marina to the boat then NEC requirements would need to be followed.

[ June 09, 2003, 07:43 PM: Message edited by: dereckbc ]
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roger
Member
Member # 79

posted June 09, 2003 07:57 PM
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Liebler, go back to Don's post, there is no 2003 NEC. Now take Don,s reference to 90.2(b), the NEC (NFPA 70) does not have any jurisdiction over the wiring on your boat. As Dereck points out, it does however cover the dock wiring. (555)

Now if you must follow the Coast Guards rule, (that you follow the NEC) do just that, and don't do anything.


Roger

[ June 09, 2003, 08:01 PM: Message edited by: roger ]
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hornetd
Member
Member # 320

posted June 09, 2003 11:54 PM
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You can insure the safety of swimmers, prevent electolysis, and keep the Coast Gaurd happy by transferring the neutral and the equipment grounding conductor between on board and shore power. Use a nonmetallic cable or raceway system and non metallic boxes and you will have created a double layer of insulation between the current carrying conductors and the hull. The cheapest way I know of to do the transfer is to cord and plug connect the onboard wiring to either a shore line extension cord or the onboard power source. That way when the cord is connected to shore power there is no conductive pathway between the hull and the shore.
--
Tom
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hurk27
Member
Member # 73

posted June 10, 2003 12:02 AM
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The Coast Guard should stay with saving boaters lives and not get into boat wiring.
as far as I know the ABYC is who set's the standereds for boats.
the Galvanic Isolator is the way I would go this way you can be sure that you metal hull is isolated.
here is a photo of one:

CONTINUED"

posted February 05, 2002 01:00 PM
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I am very concerned here in Olympia Washington. A local diving company has been getting shocked, and the shocks and stories of strange happenings here are getting worse. Last week a diver told me that he swam past a conduit in the water which he had decided to touch to make sure his tanks did not bang into and he could not let go. he was assisted and somehow survived. A diver told me that he was replacing zincs at a local marina and the zincs were foaming off of the boats like Alka Seltzer tablets. Another diver recently told me that they can feel the electricity in the water and they are really scared. I asked why they do not quit diving and they said that they have a family to take care of and this is all they know how to do. A local marina has asked Our company to engineer them a tester to make sure vessels are safe and not creating potential shock hazards.I have big problems there. For instance, It could test connections in the shore cord for shorts from hot to ground or neutral to ground via a simple continuity test, it could test the same on the vessel.The owners might be out of town and have all of the mis-wired circuits off. I cannot test from the shore cord if the 12 Volt system is wired right or not. That should not be a problem for shock hazards though right. Ok engineers, Here's your chance to help make the waters alot safer for our nations children before summer gets here. I do want so badly to hear all of your ideas as soon as possible. Much input is needed to complete this tester before someone gets hurt. Ps. I do not know if anyone has heard or not but the Seattle Yacht Club just burned 13 vessels in a fire. We all know it was probably electril. I just read that electrical fires cause over $10 Billion in damages each year in the US and result in 3000 deaths, many of them children. Sincerely,
Dave Garner,
Garner Services
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palmerbennier@msn.com
unregistered


posted February 05, 2002 03:27 PM
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The technical solution is easy. The remedy process is very difficult.
The equipment ground and current carrying ground/neutral should not be interconnected except at the main panel from the supply transformer.
The attachment cord to the boat, can be tested with an ohmmeter or continuity indicator. A low impedance from the neutral to the ground blade, indicates an interconnection.
This interconnection at one location is enough, to create earth current flow. This current flow across two nodal points, produces a voltage potential.
Special test equipment is not required.
Clearing interconnections can be verified at the panel, by lifting the individual neutral conductors and reading them to ground.
When the transformer has two earth ground connections, it is not possible to accurately measure earth current flow, without removing the connection at the panel.
I have designed and constructed residual current monitors and alarm systems. There may be some available on the market.
I used this device to monitor a 4160 volt marine cable. A single point ground is required on the transformer secondary.
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engy@kqrsrocks.com
unregistered


posted February 05, 2002 03:59 PM
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"the zinc's were foaming off of the boats like Alka Seltzer tablets"
Is the neutral-ground bond the real problem here???

Wouldn't this electrolysis be more likely caused by a poor neutral back to the source? Maybe a L-N fault with high impedance neutral so the breaker doesn't trip, and the saltwater being a relatively decent conductor to allow current flow? (same could go for L-G fault with high Z ground?)

No idea, never dealt with marinas, comments???



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resqcapt19@aol.com
unregistered


posted February 05, 2002 04:34 PM
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I agree with Bennie that the most likely source for this voltage is neutral to grounding connections on the boats.
Mike,
I don't think that a poor neutral connection on the line side of the shore power connection would cause this problem unless there is a grounded to grounding conductor connection on the boat. A poor neutral anywhere on the line side of the boat that has a neutral to ground bond on the boat would make this problem much worse.

Don(resqcapt19)


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gwz@aiagrp.net
unregistered


posted February 05, 2002 04:57 PM
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Not being familiar with marine wiring, is it probable that the Hot / Neutral is reversed somewhere between the land source and any wiring on the boat ?
Kinda sounds like getting the fishing worm trick.


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palmerbennier@msn.com
unregistered


posted February 05, 2002 05:02 PM
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I call this situation; "a low side ground fault"
Sea water has a low impedance to current flow. The boat has a parallel path to the secondary of the transformer.
A residual current sensor, at the earth connection point, can measure the amount.
Unless the interconnections can be cleared, the only remedy is an isolation transformer, connected as a separate system.
[This message has been edited by palmerbennier@msn.com (edited February 05, 2002).]


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gwz@aiagrp.net
unregistered


posted February 05, 2002 05:05 PM
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Also, is there more than one power source ie. SDS or utility transformers which could be similar to banking two transformers together except they are ' out-of-phase '?
Would that provide a source for the zinc electrolysis ?


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palmerbennier@msn.com
unregistered


posted February 05, 2002 05:42 PM
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A polarity reversal, along with the neutral/Ground interconnection, will produce a high current flow.
I would check polarity of all systems.
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palmerbennier@msn.com
unregistered


posted February 05, 2002 08:38 PM
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David: Are the cord connectors, from the boats, twist-lock?
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dustcreator@hotmail.com
unregistered


posted February 06, 2002 08:28 PM
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Everyone must be bonding to the city's water pipe system...*chuckle*
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nanotech7@juno.com
unregistered


posted February 06, 2002 10:32 PM
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Gentlemen,
Yes, there are twist lock cords exclusively.
How do I build a residual current monitor?
I was thinking of putting a Current transformer on the hot and ground leads to see if there was energy on the ground and how much current was being used. Also, in response to the statement that sea water is a good current carrying conductor, how could I test the water? My ohm meter pegs at 30 million ohms and I have a hard time reading voltage. Any ideas? I am proceeding with the tester as marina personell do not favor the DMM as much as us tradesmen do. It has very clearly defined tests that state "Neutral To Ground" "Hot To Ground" Etc. all from a simple plug in connectio to the vessels shore cord and one lead in the water. Yes, many vessels will be tested this way and so much work can be done to help check the 1,681 or boats withing a 5 mile radius. I wish I could be in every boat doing a thorough electrical check. Maybe I'll get my get my chance. I really appreciate your help. How can I simplify this tester? So far it has, Hot to neutral, hot to earth, neutral to earth, hot to water, and neutral to water. There must be a better way
Sincerely,
David Garner
GARNER SERVICES


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palmerbennier@msn.com
unregistered


posted February 07, 2002 09:55 AM
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Glenn jogged my memory. Thanks Glenn
The reason for asking about the twist-locks is because this is the cause of reverse polarity in most cases. I know they are required on marina shore power outlets.
Three wire flexible cord, is uni-directional.
The order of rotation, of the conductors, is green, white, black, in clockwise rotation at the line end. This coincides with the attachment cap terminals. The makeup and rotation is counter-clockwise at the load end.
When the cord is reversed in direction, many persons will reverse the white and black conductor. It is common, for boats, to have reverse polarity. This connection is usually done by non-electricians. However , I have seen electricians do this.
The cathodic protection plates, when oxidized, act as a rectifier diode. This is half wave, with the negative portion of sine wave appearing as a reverse voltage on the plate.
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wolford@easystreet.com
unregistered


posted February 07, 2002 02:11 PM
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It appears as though what you want to do is this.
To be able to go to any boat, without access, and test it's electrical integrity. Here's an idea that may work, let's see what the group thinks.
One problem is that inside the boat there is no way of knowing if breakers or switches are open or closed. But we do know that all neutrals should be tied at the bus, that's in the panel on the boat, and that there should be no continuity between neutral and ground.
We also know that any possible scenario of problem may be present. Even as serious as an open neutral on a boat at the panel with the ground wire not connected at the shore cord but spliced to the neutral in the boat somewhere. Causing the current to flow from the cathode of the problem boat to the cathode of the next boat over. Which could really confuse things.
I think this could work. It could be done with a hand held ammeter but it would take too long. Therefore make a unit that has a cord in and cord out to plug in between the shore cord and the shore receptacle. Have in the unit 3 current meters, one for each leg. Hot, neutral, and ground. You should get results like this. I think it would be important to see the 3 readings simultaneously.
Line current > Neutral current = Ground Fault
Line current = Neutral current, with 0 Ground current = Good
Line current = Neutral current, with current in Ground also = Picking up current from another boat.
Any current in the Ground conductor = A Problem at this boat or its neighbor
Line current (yes) Neutral current (no) or Line current (no) Neutral current (yes) = A bad problem at this boat
There could be many other scenarios. But now you could isolate the problem boats, and get them fixed

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nanotech7@juno.com
unregistered


posted February 07, 2002 02:36 PM
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Thank you Bennie, Those darn twist locks. I'll be looking now!
Rick, That's a good idea. I wanted to use something like this but was unsure how. I was concerned about safety. I purchased a 50 AMP Square D GFCI and plastic enclosure as well as 3 Current transformers but they are all sitting over there on the test bench. So you believe that the hot and neutral should read the same for a safe boat? Do you also believe that there should be no current on the grounding lead? Is that the test? If it is great! What do you think guys? Is this the best way?


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palmerbennier@msn.com
unregistered


posted February 07, 2002 03:07 PM
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Connect a GFCI inline. Reverse polarity or ground/neutral connection will initiate a trip.

nuary 24, 2004 02:58 PM
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I am an electrician for a town on Long Island where we have many marinas. Every year we have the same problem with the power centers where the neutral on the outlet burns but only the neutral. The hot and ground is always fine. Even I when we replace the outlet and tighten all connections and the boat owner uses a new cord the problem still occurs. Does anyone have a clue as to what can be causing this and a possible cure. Thanks
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tonyi
Member
Member # 10066

posted January 24, 2004 04:36 PM
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240V feeds? ...are the neutral's sized big enough to avoid overheating?
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jimwalker
Member
Member # 13241

posted January 24, 2004 06:10 PM
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I am thinking somehow the boats ground has a potential differance to the land neutral (grounded conductor).If this is on several boats then i would be checking the service grounding.Might take amp probe and with boat pluged in but no load see if there is a reading.

--------------------
Tampa Florida

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jwedell
Member
Member # 14265

posted January 24, 2004 06:23 PM
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Thanks jimwalker I'll give it a try.
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jwedell
Member
Member # 14265

posted January 24, 2004 06:27 PM
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Originally posted by tonyi:
[QB] 240V feeds? ...are the neutral's sized big enough to avoid overheating? They are 2/0 Copper feeders with a 150 amp breaker.
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joe stewart
unregistered


posted February 12, 2004 07:42 PM
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What I have found at our marinas around here is loose neutrals at the service caused by corrrosion from salt water. The phenomena occurs here in Seatlle too. Evrey time I replace a 30 amp dock receptacle its the neutral that sustains the most damage. Maybe the electrons are just trying harder to get back to the transformer and they die and turn eveything black?
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hurk27
Member
Member # 73

posted February 13, 2004 12:33 AM
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Have you tryed a anti-oxident like Ideal No-A Lox? there could be stray current flowing through the boat from the POCO's service. At my dad's marina down in key largo (until Andrew hit) we used isolation transformers to prevent electrolisis between the boat hull or any metal in contact with the water and the shore grounding. but it has to be treated like an SDS system to provide a ground fault path. Put a amp meter on the EGC to the boat and see if there is any current on it. then shut off the power to this boat and check it again. if the current is still there it's coming from ether the POCO's service or another boat with some bad wiring.

--------------------
Wayne A. From: N.W.Indiana
Be Fair, Be Safe
Just don't be fairly safe

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rey-man
Member
Member # 542

posted February 23, 2004 08:52 AM
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I would suggest to check out the American Boat and Yachting Council. They are pretty well verse with problems like this...

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