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Post by Xlnt on Mar 3, 2014 10:01:44 GMT
Hello I am wondering if anyone have had problems in the ground circuit? I have noticed when the boat is on the hard, with the shorepower connected and there is wet/moist conditions, if I touch any thing of metal and have my feet on the ground I get electric shock. Not dangerously but I can feel the current and it is unpleasant to touch. This cant be normal, right? Any tips are welcome Rgds -XLNT
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Post by rene460 on Mar 3, 2014 10:37:13 GMT
Hi Xint,
in the situation you describe, I would first be checking the polarity of your AC connections, if active and neutral are swapped I think it could lead to this issue. There should be an indicator on your power board, but if you have any doubts, an indicator device is generally available at an electronics store (trade or hobby type, not consumer outlets) at a very reasonable price.
Obviously check your cable, but your marina supply can be wrong (in which case they need to get their act together) but it can also happen on board at any AC connection point, so check all your power outlets.
Otherwise a careful check of all the earth bonding system seems to be required, perhaps others can provide some tips, as I find that part to be somewhat mysterious. I am never totally sure which points should be connected to the earth system.
In any event I suggest it is important to track down, do not ignore it!
rene460
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Post by Xlnt on Mar 3, 2014 11:04:26 GMT
I need to add that this is 220v and we do not have polarity here in Norway.
Is the ground cable supposed to be connected anywhere in the boat or should it just be cut?
-XLNT
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Post by On y va on Mar 3, 2014 13:40:02 GMT
The ground cable connects i.e. to your 220volt breaker panel. You will see a yellow/green wire connected to the panel, usually on the side of the panel. All other metal 220v units (battery chargers, inverter, boiler) and 220v sockets are connected to the ground cable.
So u cannot cut the ground cable, but maybe there is a failure in it somewhere.
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Post by dnickj on Mar 3, 2014 20:33:59 GMT
The ground cable connects i.e. to your 220volt breaker panel. You will see a yellow/green wire connected to the panel, usually on the side of the panel. All other metal 220v units (battery chargers, inverter, boiler) and 220v sockets are connected to the ground cable. So u cannot cut the ground cable, but maybe there is a failure in it somewhere. Hi sorry to tell you but unless physics has been rewritten you do have polarity in Norway your wiring colour code is international standard with brown being live ans blue neuteral
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Post by On y va on Mar 3, 2014 21:52:03 GMT
dnickj: I don´t know why you quoted my comment, as I do not mention anything about polarity, but I think what Xlnt is trying to say, that it makes not difference really how you plug in or connect. I.e. in english yachts, they always have a polarity warning if you mix blue and brown and even system that will switch it round for you, so you don´t have to fiddle around with changing plugs. However in "the rest of Europe" it really makes no difference how you plug in or connect your plugs. But you are correct in your statement that brown is live and blue neutral and to be complete, earth is yellow/green, which is what this topic is about.
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Post by bikerwookie on Mar 3, 2014 21:53:08 GMT
Sounds like you have a leak between the ac and the earth that is not large enough to trip the breaker. I had a similar problem early in the season and believed it to be the shore power cable that had been in the water. Replaced the cable and problem went away. However on testing the cable I could find no fault with any connection even slight between earth and the other two contacts. So Ian still worried I have not sourced the problem
I had just fitted a galvanic isolator two weeks earlier but cannot see why that would effect the breaker not tripping.
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Post by Tafika II on Mar 3, 2014 22:08:18 GMT
Hi Bikewookie! I am about to install a galvanic isolator & want to make sure I have it done correctly. I understand one wire connects to the ground entering the boat from the shoreline ground, but where did you hook up the ground on the other side?
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Post by Trevor on Mar 3, 2014 23:49:18 GMT
Hello Xlnt, The earth wire connected to the inlet socket on your boat connects to those metallic objects on your boat as a safety mechanism so those metal objects can never carry lethal potential with respect to earth. For those metal objects to have any significant potential with respect to "earth" ( the ground you are standing on) the resistance of the earth conductor or the sockets carrying the conductor must be too high. I suggest you carefully inspect the earth connection between the power inlet socket on the boat and also the earth pin connection on the Marina shore power connector. Sometimes the earth pin can become corroded causing a high resistance joint. I suggest spraying the pins with CRC or WD40 or a product like that. The connection within the shore power connector can also be corroded. Please do not under any circumstances cut the earth cable! That would be very bad indeed. This should be taken seriously as people have been killed by the earth connection falling off and the metal of the yacht being raised through a fault to mains potential. This is extremely dangerous on the hard as we humans tend to come between earth ( actual earth under your feet ) and a "live" boat. The boat owner provides the path to earth of the leakage current, and hence is killed. Good luck with reducing the resistance of the earth connection on your boat. I would make this task a top priority, prior to doing anything else. Regards, Trevor
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Post by psychotiller on Mar 4, 2014 5:43:33 GMT
Having gone through my own AC issues recently I feel your pain. I agree with Trevor, this should be a high priority project as it has the potential to be very dangerous. It definitely sounds like there is an AC ground/earth leak that isn't supposed to be there. Although I am definitely far from a master electrician from what I understand if you have a GFI in every AC circuit that should prevent this problem. If you have GFI's are they testing ok? Of course the GFI would prevent the shock but doesn't really fix the problem. I think if the shore power polarity is reversed or not grounded/earthed properly that could also cause problems. And from what I understand marina shore power is often not grounded properly or has reversed polarity. Maybe you will get lucky and it's the shore power supply and not your boat. Perhaps check the marina power outlet too.
Hopefully someone with more electrical experienced than I will comment on these suggestions to make sure I'm not sending you in the wrong direction.
Good luck!
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Post by psychotiller on Mar 4, 2014 5:49:19 GMT
One other possible easy fix could be your power cord? Maybe the ground in your cord is faulty? Maybe check that too if you have not already. But as I understand it (which could be very wrong) this would prevent the shock you are getting but not necessarily fix the short causing the shock.
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Post by Xlnt on Mar 4, 2014 7:29:14 GMT
Thanks for all the advice guys. I will start to track this down. I have read elsewhere that under no circumstances that the shorepower earth should be connected to bonding system in a boat. That will make all your zinc be eaten up very quickly if there is a problem in a marinas powersupply. It stated that all system should be completely separated, 12v ground, bonding system, 220v system never to be combined?
-XLNT
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Post by On y va on Mar 4, 2014 8:37:42 GMT
That is correct. Your 220v earthing runs via the electrical circuit on land, not the water!!.
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Post by Xlnt on Mar 4, 2014 9:47:14 GMT
The boat is equipped with a ground plate underneath, what is supposed to be connected to this? Is it for lightning, bonding-system, 220v or 12v. Here is a picture of similar plate: www.threefools.org/catspaw/BoatDetails/SSBGroundPlate.jpg It also have copper foil running underneath the aft berth but I don't know from where to where, is it standard on SO42DS? -XLNT
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Post by Trevor on Mar 4, 2014 10:08:25 GMT
Hello gents, I am concerned at the concept of a separation of DC earth and Mains earth as it is a very dangerous practice and we shouldn't propagate that as a reasonable method of eliminating galvanic currents. It totally defeats the safety purpose of mains earth wiring. This is a complex subject but the separation of earths can be achieved with a Galvanic isolator. No boat wiring should ever leave the mains earth floating. Happy to discuss in detail if required but thought we should attempt to clear that up. Regards, Trevor
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Post by puravida35 on Mar 4, 2014 14:17:24 GMT
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Post by Tafika II on Mar 4, 2014 17:34:45 GMT
The large copper ground plate and the copper foil are used for a SSB hookup and NOT the AC grounding.
Trevor, I noted above I will be installing a Galvanic Isolator. If you have installed one, let me know how you hooked it up. I'm 98% position of the installation, but it never hurst to ask before I do the project.
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Post by Trevor on Mar 4, 2014 21:13:34 GMT
Hello Tafika II,
The isolator is simply placed somewhere between the inlet socket on your boat and the switchboard. It is advised to be installed as close as practical to the inlet socket however on the SO 42 DS I think the best place is mounted to the left behind the drop down switch panel at the Nav station. The earth cable from the inlet socket is located there and it is a simply matter to cut that earth cable and put the galvanic isolator in series before the earth cable is terminated on the board.
The 1.2 volt ( two silicon diodes in series 0.6Volt each) forward voltage drop across the isolator prevents galvanic currents flowing however any fault currents or leakage currents can still flow once the 1.2 volt threshold is reached. The reason this works is the voltage developed across dissimilar metals under water (causing the galvanic current) is less than the 1.2 volts required to make the isolator conduct.
I hope this helps.
Regards,
Trevor
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Post by pbunning on Mar 4, 2014 22:03:00 GMT
It is important to regularly test/check galvanic isolator. Attachment DeletedAttached photo of galvanic isolator fitted to SO33i.
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Post by Tafika II on Mar 4, 2014 22:56:02 GMT
Thanks for the pictures, pbunning and Trevor, thanks for the description . I good to do this project this weekend!
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Post by Xlnt on Mar 5, 2014 12:24:30 GMT
The large copper ground plate and the copper foil are used for a SSB hookup and NOT the AC grounding.
Yes thats probably right, the boat has a huge Furuno SSB radio
-XLNT
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Post by Xlnt on Mar 11, 2014 10:42:08 GMT
Hi, have been measuring for ground problems now but cant seem to find and problems. Does anyone know if a 12v charger can suddenly connect shore ground to 12v ground if something goes wrong inside the charger it self? Another thought is that what I have felt is the 12v current, I have aprox 900ah of batteries, can that be felt on rainy days?
Rgds -XLNT
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Post by Don Reaves on Mar 11, 2014 13:48:31 GMT
Failure modes in electrical equipment can vary a lot based on the way they are designed. It's certainly possible that the grounds might become connected if a failure occurs. Typically, though, I would guess that most failures tend to disconnect things rather than connecting them, so it wouldn't be my first guess.
I would be very surprised if you could feel any current from a 12V system. If your boat is still on the hard, you should be able to measure the voltage from earth to the metal parts on your boat. Just stick something metal in the ground and attach your voltmeter to it and to the metal parts of your boat that gave you a shock. Be sure to have the meter on an appropriate AC scale.
Don
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Post by Mistroma on Mar 17, 2014 18:09:50 GMT
It is important to regularly test/check galvanic isolator. View AttachmentAttached photo of galvanic isolator fitted to SO33i. The galvanic isolator on my 42DS is also fitted in the locker beside the connector. However, I was able to mount it on the other side of the panel and I screwed it to the adjacent wooden panel at 90 deg. to the one holding the connector and trip switch. This keeps the wiring clear of any water spray or drips (not likely but possible) but does make access a little more difficult. Fortunately, the isolator has a remote status panel and so doesn't need to be accessed often for testing.
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Post by Trevor on Mar 21, 2014 8:49:05 GMT
Hello all, I have decided to outline the installation of a Galvanic Isolator which I installed onto my SO 42DS. But first a cautionary note. Certainly in Australia, one of these can ONLY be legally fitted by a licensed electrician. My son is a licensed electrician and he has given this a clean bill of health. Now for the installation, A Galvanic Isolator is to be installed as close as possible to the inlet socket, however in this case the most logical place I think to mount this device is behind the navigation station drop down panel. The reason is it is not exposed to any moisture and it is where the cable from the inlet socket is joined to the wiring loom of the boat so it is a logical place to insert the isolator. If you remove the plastic cable tray covers you can see where the inlet cable joins the wiring loom of the boat. This picture shows the factory connection for the earth. I must say i was not impressed with the quality of the soldering. Very poor to be honest. Simply break this connection and insert the Galvanic Isolator. Solder the connection carefully and use the same gauge wire. I used a couple of layers of heat shrink to make it all look nice. From now on, when hooked up to shore power, galvanic currents cannot flow through the earth connection because of the forward voltage drop across the diodes in the isolator. This stops you and every other boat at the Marina forming a great big battery caused by dissimilar metals, and therefore stops destructive currents slowly eating away your expensive metal bits. I hope this may help someone who would like to fit one of these isolators. Remember, in Australia you must be a licensed electrician. Regards, Trevor
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