Current In The Water???

[Ken Coit]

Speaking of current in the water, does anyone know of a good way to test for AC current before diving on your boat? Is a voltmeter between safety ground at the pier and the water sufficient? What do commercial divers do when they have to dive in a marina?

I'm sure all our Cape Dorys are wired correctly, but what about that derelict beside us? What about the marina itself?


Keep on sailing,

Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC



parfaitNOSPAM@nc.rr.com

[John R.]

Speaking of current in the water, does anyone know of a good way to test for AC current before diving on your boat? Is a voltmeter between safety ground at the pier and the water sufficient? What do commercial divers do when they have to dive in a marina?

I'm sure all our Cape Dorys are wired correctly, but what about that derelict beside us? What about the marina itself?


Keep on sailing,

Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC

Yes Ken you have it correct, that is the procedure for checking for serious leaks at the dock hook up. Be sure to set the meter at a high voltage scale and then increase sensitivity gradually switching to the lower scales. There should be NO readings. If there are readings then you have discovered serious leaks.

If you don't want to use a VOM meter you have the option to purchase a GF indicator (ground fault) and plug it into the shore receptacle before hooking up. It will indicate if there is leakage. I'm not sure what they are selling for these days.

Best way to protect any swimmers or divers from a derelict or other boat with questionable AC wiring is simply to disconnect it from shore hook up before entering the water. I have my CD30 AC safety ground wired to vessels common ground point as per ABYC standards. It is a matter of a safety issue for persons on board operating AC components that I subscribe to this wiring philosophy. There are proponents of advocating not running the AC safety ground to the common ground point as a result of concern over stray current entering the waters surrounding the boat if an AC component or wiring should fail and pose a voltage leak. This of course is a valid viewpoint but the safety of persons on board takes priority over possible stray current scenarios. This is why ABYC after much debate and study has been advising for many years that the on board AC safety ground be wired to the common ground point. In addition, being aware of any AC problems on board can easily be accomplished......read on.

With all that now said there comes the issue you pose in your comments about the safety of divers. Even though I know my AC system is without leaks and is wired according to ABYC standards I nonetheless always unplug the shore cable to be on the safe side whenever my diver services the hull or zincs.

If a boat is wired to ABYC standards and you are concerned about the chance of an unknown leak taking place then you can do an on board ohm test for leak potential.

Very Important!!! Only do this test with the shorepower cable disconnected (safety) and all AC equipment and components on board must be switched off also (for testing purposes). BE CAREFUL and make sure this is done.

Now you set your VOM meter to Rx1 ohm scale. Next you start testing. You test between the safety ground and hot and then repeat the test again testing between safety ground and neutral. These tests should result in absolutely no ohms being read (thus an infinity reading), in other words there should be no continuity. If these two test results are normal then you know your on board AC system is safe with no leaks.

If you have any trace of continuity (readings) then you have leakage. At that point it would then become a long day or series of days (better stock up on the cool ones) because now you have to begin the long arduous *process of elimination* trying to determine where the leak is originating from.

In a nutshell without all the details to protect divers and swimmers near the boat, simply test the shore outlet as outlined and unplug the shore cable. Everyone and everything is protected as far as *your boat* is concerned. Who knows what is going on next to you or a few slips away. Keep in mind the danger is much worse in freshwater than saltwater oddly as that may sound.

[John D.]

Gentlemen, What an interesting, albeit complicated subject for some readers. I am referring to recent postings by Randy Bates,Larry DeMers,Ken Coit and John R. in regard to shipboard A.C. panel wiring and "Current in The Water". It is obvious to me that the people that offer their opinions regarding these subjects have above average knowledge,experience and expertise in these matters. We must remember
that many people that read these postings do not possess the basics to understand much of the depth in your replies. I do have to say that I agree with each one of your ideas on these subjects, according to each individual scenario in your explanations and viewpoints. I think that this is a good example of what this message board is all about. Now I shall try to express my viewpoints on the subjects. John R. alluded to a very important item that I feel he didn't go far enough with. I am talking about G.F.I.C. or Ground Fault Interrupters.Any dock , pier or marina that furnishes A.C. power, whether to power tools or for onboard A.C. power that Randy was talking about, must incorporate a G.F.I. as an integral part of the power supply. This is the law. This is required by the National Board of Fire Underwriters. It is for the safety and wellbeing of all concerned. If you are tied up at your own private dock, you must have a G.F.I. as part of your power supply. That, too, is the law. If your boat is parked next to your house off season and you want to work on it with power tools, you must be plugged into a power source governed by a G.F.I. Any person that works with power tools, whether around the house or on the boat, should have his own personal G.F.I.in his tool box. You can buy them at any electrical supply house or home supply store like Home Depot etc. The last time I bought one several years ago, I believe I paid around $35.00. It will last you a lifetime, no pun intended. If the marina wherever you are tied up at furnishes power, get yourself a polarity checker and check out the outlet you are using for proper polarity This is a simple little gadget that plugs into your outlet. It has colored lights that glow to tell you if the house power being supplied is wired properly. Don't assume anything is proper or not, test it and be certain. If the house power is O.K., then plug your G.F.I.into the house receptacle and then plug your extension cord or ship supply lineinto the G.F.I. There is a built in tester in the G.F.I. so push the test button and test that the power shuts off. then push reset. The beauty of this setup is that should something on your boat malfunction, or maybe something was afterwired incorrectly after construction, you'll find out immediately. Should there be a malfunction in your ship's wiring, the G.F.I. will kick out and there is no way that it will hold till you alleviate the problem.This is a control warning for stray currents, also. The principle of how it works is, assuming that you are drawing 7 amps of current, 7 amps will becoming to your ship on the black (hot) leg of the the supply cord. The electric current passes through whatever is consuming the 7 amps and returns to the house supply on the white (ground) conductor of the supply cord. If 7 amps is coming in on the hot conductor and only 6 amps is returning on the white (neutral) conductor, something is wrong with the wiring system. The G.F.I. detects this imbalance and shuts down the system, literally, quicker than an eyeblink. Where did that stray ampere go to? Possibly leaking into the surrounding water, who knows? But utilizing a G.F.I. it wont leak for long. the unit is doing it's job. John R., you explained some good points in showing how to test the water before diving. I would like to add something to when you set your V.O.M. (volt-ohmeter) on ohm mode.After setting it for ohms, take the two leads and short them out, that is, touch them together. The needle of the meter should swing full scale. The reason for this brief test is to ascertain the condition of the battery inside the meter. When your meter is set to check other modes, such as voltage or milliamps, the meter is powered by the electrical source being tested. When it is in the Ohm mode, it is testing resistance and uses its own battery to power the meter. If the battery is dead, an inexperienced person might not realize this and go about testing, thus getting false or no reading and be mislead by the dead meter. For what it's worth, swimming pool shops use a type of meter that they immerse in a pool near underwater lights, testing for electrical leakage. Just a thought. Sorry to be so longwinded but I really enjoy deep discussions like this. But whatever we say, we must keep in mind that many readers are "Newbies"to a lot of discussions and maybe we should try to practice K.I.S.S. in some of our answers. I do have to admit that going a little deeper into a subject never hurts and is educational and enjoyable to many. Keep up the good posts. John D.



Choppedliveroy@aol.com

[John R.]

Gentlemen, What an interesting, albeit complicated subject for some readers. I am referring to recent postings by Randy Bates,Larry DeMers,Ken Coit and John R. in regard to shipboard A.C. panel wiring and "Current in The Water". It is obvious to me that the people that offer their opinions regarding these subjects have above average knowledge,experience and expertise in these matters. We must remember
that many people that read these postings do not possess the basics to understand much of the depth in your replies. I do have to say that I agree with each one of your ideas on these subjects, according to each individual scenario in your explanations and viewpoints. I think that this is a good example of what this message board is all about. Now I shall try to express my viewpoints on the subjects. John R. alluded to a very important item that I feel he didn't go far enough with. I am talking about G.F.I.C. or Ground Fault Interrupters.Any dock , pier or marina that furnishes A.C. power, whether to power tools or for onboard A.C. power that Randy was talking about, must incorporate a G.F.I. as an integral part of the power supply. This is the law. This is required by the National Board of Fire Underwriters. It is for the safety and wellbeing of all concerned. If you are tied up at your own private dock, you must have a G.F.I. as part of your power supply. That, too, is the law. If your boat is parked next to your house off season and you want to work on it with power tools, you must be plugged into a power source governed by a G.F.I. Any person that works with power tools, whether around the house or on the boat, should have his own personal G.F.I.in his tool box. You can buy them at any electrical supply house or home supply store like Home Depot etc. The last time I bought one several years ago, I believe I paid around $35.00. It will last you a lifetime, no pun intended. If the marina wherever you are tied up at furnishes power, get yourself a polarity checker and check out the outlet you are using for proper polarity This is a simple little gadget that plugs into your outlet. It has colored lights that glow to tell you if the house power being supplied is wired properly. Don't assume anything is proper or not, test it and be certain. If the house power is O.K., then plug your G.F.I.into the house receptacle and then plug your extension cord or ship supply lineinto the G.F.I. There is a built in tester in the G.F.I. so push the test button and test that the power shuts off. then push reset. The beauty of this setup is that should something on your boat malfunction, or maybe something was afterwired incorrectly after construction, you'll find out immediately. Should there be a malfunction in your ship's wiring, the G.F.I. will kick out and there is no way that it will hold till you alleviate the problem.This is a control warning for stray currents, also. The principle of how it works is, assuming that you are drawing 7 amps of current, 7 amps will becoming to your ship on the black (hot) leg of the the supply cord. The electric current passes through whatever is consuming the 7 amps and returns to the house supply on the white (ground) conductor of the supply cord. If 7 amps is coming in on the hot conductor and only 6 amps is returning on the white (neutral) conductor, something is wrong with the wiring system. The G.F.I. detects this imbalance and shuts down the system, literally, quicker than an eyeblink. Where did that stray ampere go to? Possibly leaking into the surrounding water, who knows? But utilizing a G.F.I. it wont leak for long. the unit is doing it's job. John R., you explained some good points in showing how to test the water before diving. I would like to add something to when you set your V.O.M. (volt-ohmeter) on ohm mode.After setting it for ohms, take the two leads and short them out, that is, touch them together. The needle of the meter should swing full scale. The reason for this brief test is to ascertain the condition of the battery inside the meter. When your meter is set to check other modes, such as voltage or milliamps, the meter is powered by the electrical source being tested. When it is in the Ohm mode, it is testing resistance and uses its own battery to power the meter. If the battery is dead, an inexperienced person might not realize this and go about testing, thus getting false or no reading and be mislead by the dead meter. For what it's worth, swimming pool shops use a type of meter that they immerse in a pool near underwater lights, testing for electrical leakage. Just a thought. Sorry to be so longwinded but I really enjoy deep discussions like this. But whatever we say, we must keep in mind that many readers are "Newbies"to a lot of discussions and maybe we should try to practice K.I.S.S. in some of our answers. I do have to admit that going a little deeper into a subject never hurts and is educational and enjoyable to many. Keep up the good posts. John D.

Thanks for pointing out what some of us take for granted and which may inadvertently place others at a disadvantage when we discuss certain issues. That is surely something that must be kept in mind whenever making message posts. For me, sometimes it can be difficult to make some of these topics easy to understand for everybody. The necessary descriptive jargon required to elaborate on some issues can more often than not be next to impossible to alter and still make the point.

I understand full well your points on the GFCI importance. Everybody should be fully aware how important it is to have a GFCI incorporated into your on board AC system. Typically it is understood by most that GFCI's are legally required in electrical codes these days. I have to say I am surprised to learn that according to N.B.F.U. that marinas are legally responsible for having GFCI incorporated in the shoreside hookups also. I think I'm interpreting your comments correctly. If so, then down here in SW Florida there are a lot of marinas that are breaking the law because I know of not one that has visible GFCI hookups in my area. Maybe they are using a behind the scenes ground fault system on the circuit. Usually, down here anyway, most boats with AC circuits are equipped with on board GFCI's. I certainly can see the logic in requiring a marina or any docking facility public or private to have GFCI protected hook ups. A few years ago I retro fitted my AC hook up on my dock placing my 30 amp shore receptacle in series with an industrial grade GFCI outlet. In addition on the boat there is another GFCI which all other AC circuits on board run in series off of.

Funny though about your comment on the GFCI "detecting the imbalance". I fully understand how a GFCI compares amperage on the hot side of a circuit to the neutral side return amperage. If they are not equal in comparison then it is supposed to trip. I'm not sure what they trip at, I suppose it must be in the hundreths or thousandths of an amp since a tenth of an amp can kill a person. Milliamps are the problem in stray current on most boats. I traced leaking voltage on boats before that were equipped with GFCI's and on some the voltage was passing through the reverse polarity lights (see posts from the other day) but boats equipped with GFCI's never tripped. In your opinion why do you think that was the case? Not enough amperage passing is my obvious guess? I'm not so sure a GFCI is dependable in acting as a failsafe against stray current entering the ground system to ward off stray current on a typical boat. Maybe I'm not fully understanding your point of view regarding the GFCI.

Excellent post......that was real heads up of you pointing out the battery situation in a meter, thats the sort of thing that is so very easy to overlook when making a post. Proves the point "two heads are better than one".

[Tom]

A word of caution about trusting GFIs. I managed a marina here in Calif for about 5 years. The outlets had GFI outlets per the law, but it should be noted that there is no overload protection in a GFI outlet. Boaters were forever plugging heaters and heavy amp draw appliances into them via household extension cords rather than their 30 amp dock cord. When GFIs are overheated in this way they tend to weld themselves in the open position. Once they are welded open, they will not trip even if the ground is interrupted. Therefore before you trust one, you want to actually press the test button and make sure that it will trip off, rather than just look and see if there is one present on the line. We were forever unplugging extension cords and writing people notes about using only 30 amp dock cords to bring power to the boat and then replacing fried GFI outlets. They continue to work (in the sense you plug in and you get electricity) and look fine even when they aren't protecting you.

Speaking of current in the water, does anyone know of a good way to test for AC current before diving on your boat? Is a voltmeter between safety ground at the pier and the water sufficient? What do commercial divers do when they have to dive in a marina?

I'm sure all our Cape Dorys are wired correctly, but what about that derelict beside us? What about the marina itself?


Keep on sailing,

Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC

TomCambria@mindspring.com

[Ken Coit]

National Semiconductor Spec sheet indicates that their GFI trips between 3 and 7 ma, typically 5 ms. With a 500 ohm fault, it will trip in 16 millisconds.

See the link below for more info.


Keep on sailing,

Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC



parfaitNOSPAM@nc.rr.com

[Ken Coit]

National Semiconductor Spec sheet indicates that their GFI trips between 3 and 7 ma, typically 5 ms. With a 500 ohm fault, it will trip in 16 millisconds.

See the link below for more info.


Keep on sailing,

Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC

parfaitNOSPAM@nc.rr.com

[Hobbster]

Gentleman: GFI circuts are NOT provided for 30+ amp recepticals. Do not think that your marina is portecting your 30 or 50 amp connection with a GFI. They are (by code) to provide 15/20 amp, 115VAC outlets with GFI protection. Now, it is important to know that the further down the peir you are, the more problems you can have with stray current. It is odd that the boats wired to ABYC standards will be the boats that will loose thier zincs first. If a poorly wired boat near you (or 2, 3, or 4 poorly wired boats) and your boat is connected to shore power and your boat ground is electricaly closer to these boats (less resistance to ground by way of your boat instead of the ground wire to shore) your boat will be providing the ground circut for these poorly wired boats. The only way to prevent this is with an isolation transformer on your incoming shore power fitting. This is done on some new boats. I know that this subject could go on and on (that's why they write books on the subject).

May the electricity flow in your wires like the water under a CD bottom!

Hobbster



glen@hobbymarine.com

[D. Stump, Hanalei]

shore power and the problem goes away!!!!

Hanalei

[Ken Cave]

This is not the only problem!!

Two months ago, I had installed a zinc around the prop shaft-only to be called by my diver that the zinc was already eaten up! When I talked to the marina about this problem, they stated that someone was "hot" and was eating the zincs off a lot of boats-and when the zincs are gone, then other major items are attacked!! Now this happens when you are plugged into the AC on the dock.

What to do? Install a Galvanic Isolator on the ground wire of your AC plug. These units actually block galvanic current flow, resulting in less corrosion and zinc loss, while allowing the AC ground to carry full amperages. Cost? about $175.00-but it is better than sinking!!

Ken Cave
CD 28 Dragon Tale
Anacortes WA



bcave@whidbey.net

[Ken Cave]

Unfortunatally the Cape Dory is not wired to compensate for electrical problems caused by other boats, as the thru hulls are not "wired" together. However, when I had my boat checked out by a very qualified mechanic, he also stated that the thru hulls on a Cape Dory will probably last more than my lifetime even if they are subject to electrical problems from a "hot" boat nearby due to their construction.

He did, however, find that the wires attached to the plate in the bilge were somewhat corroded at the fittings. I replaced all the fittings, and did find one wire that was corroded to the point of breaking off when I removed it from the unit.

If in doubt, get a professional to check your boat. It is worth the money for the peace of mind. (I know have two grounding wires off the engine!)

Ken Cave
CD 28 #227
Anacortes,WA



bcave@whidbey.net

[John R.]

Unfortunatally the Cape Dory is not wired to compensate for electrical problems caused by other boats, as the thru hulls are not "wired" together. However, when I had my boat checked out by a very qualified mechanic, he also stated that the thru hulls on a Cape Dory will probably last more than my lifetime even if they are subject to electrical problems from a "hot" boat nearby due to their construction.

He did, however, find that the wires attached to the plate in the bilge were somewhat corroded at the fittings. I replaced all the fittings, and did find one wire that was corroded to the point of breaking off when I removed it from the unit.

If in doubt, get a professional to check your boat. It is worth the money for the peace of mind. (I know have two grounding wires off the engine!)

Ken Cave
CD 28 #227
Anacortes,WA

Ken,
Virtually every Cape Dory I have been on had all thru hulls factory bonded by #8 solid core copper, thus they are wired together.

I am puzzled by why yours aren't. Maybe at one time someone removed your bonding system. Puzzling further because you state you have "wires" running to a plate in the bilge (assuming that is a ground plate). That tells me perhaps the only thing running to the ground plate is a lead from your common ground point buss and maybe a electronics ground of some type.

I don't know why your mechanic is telling you a CD thru hull will last a lifetime even if they are subject to a galvanic problem. Under those conditions they won't last any longer then say a Perko, Wilcox, Groco or other brands. A galvanic problem is a galvanic problem and and all marine underwater metal is subject to damage by it.

[Ken Coit]

Unfortunatally the Cape Dory is not wired to compensate for electrical problems caused by other boats, as the thru hulls are not "wired" together. However, when I had my boat checked out by a very qualified mechanic, he also stated that the thru hulls on a Cape Dory will probably last more than my lifetime even if they are subject to electrical problems from a "hot" boat nearby due to their construction.

He did, however, find that the wires attached to the plate in the bilge were somewhat corroded at the fittings. I replaced all the fittings, and did find one wire that was corroded to the point of breaking off when I removed it from the unit.

If in doubt, get a professional to check your boat. It is worth the money for the peace of mind. (I know have two grounding wires off the engine!)

Ken Cave
CD 28 #227
Anacortes,WA

Ken,
Virtually every Cape Dory I have been on had all thru hulls factory bonded by #8 solid core copper, thus they are wired together.

I am puzzled by why yours aren't. Maybe at one time someone removed your bonding system. Puzzling further because you state you have "wires" running to a plate in the bilge (assuming that is a ground plate). That tells me perhaps the only thing running to the ground plate is a lead from your common ground point buss and maybe a electronics ground of some type.

I don't know why your mechanic is telling you a CD thru hull will last a lifetime even if they are subject to a galvanic problem. Under those conditions they won't last any longer then say a Perko, Wilcox, Groco or other brands. A galvanic problem is a galvanic problem and and all marine underwater metal is subject to damage by it.

parfaitNOSPAM@nc.rr.com

[John R.]

Unfortunatally the Cape Dory is not wired to compensate for electrical problems caused by other boats, as the thru hulls are not "wired" together. However, when I had my boat checked out by a very qualified mechanic, he also stated that the thru hulls on a Cape Dory will probably last more than my lifetime even if they are subject to electrical problems from a "hot" boat nearby due to their construction.

He did, however, find that the wires attached to the plate in the bilge were somewhat corroded at the fittings. I replaced all the fittings, and did find one wire that was corroded to the point of breaking off when I removed it from the unit.

If in doubt, get a professional to check your boat. It is worth the money for the peace of mind. (I know have two grounding wires off the engine!)

Ken Cave
CD 28 #227
Anacortes,WA

Ken,
Virtually every Cape Dory I have been on had all thru hulls factory bonded by #8 solid core copper, thus they are wired together.

I am puzzled by why yours aren't. Maybe at one time someone removed your bonding system. Puzzling further because you state you have "wires" running to a plate in the bilge (assuming that is a ground plate). That tells me perhaps the only thing running to the ground plate is a lead from your common ground point buss and maybe a electronics ground of some type.

I don't know why your mechanic is telling you a CD thru hull will last a lifetime even if they are subject to a galvanic problem. Under those conditions they won't last any longer then say a Perko, Wilcox, Groco or other brands. A galvanic problem is a galvanic problem and and all marine underwater metal is subject to damage by it.

Correction, had a bad morning, still the cobwebs........that last message should read *stray current* rather than "galvanic" where it is stated. Sorry for the loss of mind.

[Ken Cave]

Thanks for the info! Mine is not grounded as you stated, but it is worth looking into!

I asked the mechanic that did the survey on the electrical problem and his answer was that the thru hull units were the best product he has seen on a boat-and should last a lifetime, even in adverse conditions!

Ken Cave
Dragon Tale CD#227 (l979 model)



bcave@whidbey.net