Author Topic: Galvanic isolator (Read 13686 times)

Aquila · « **on:** January 10 2016, 20:09 »

Hi all, looking to fit a galvanic isolator to my Bav 36 (2012), no real reason except I don't have one. I am fitting a new Darglow feather stream prop which costs a lot and I think this may help protect it. Would welcome any views before i buy one from safeshoremarine. thanks

tiger79 · « **Reply #1 on:** January 10 2016, 21:07 »

Not a bad idea - it can't do any harm, and may do a lot of good.

Baltic · « **Reply #2 on:** January 10 2016, 22:34 »

Hi.

Please note.
Basically that safeshoremarine "galvanic isolator" is not isolator at all..
Just some diodes on the earth wire..
Like Sterling zinc saver. http://sterling-power.com/products/zinc-savers-galvanic-isolators
or Victron https://www.victronenergy.com/isolation-transformers/galvanic-isolator

After one season Sterling use.
It works as good as expected. Impossible to see any difference between with or without zinc saver.
Zinc were as lost as those typically are after season.

Next I will buy isolation transformers...
Those should isolate shore power from boat power.
Let see.

Maybe someone have good zinc saver experience.
For me it was only 100 ? experiment with zero end results.

Symphony · « **Reply #3 on:** January 10 2016, 23:16 »

The purpose of a galvanic isolator is to protect from stray currents when plugged into shorepower. It is unlikely to do anything for your new prop which is already isolated from the rest of the boat. It has its own anode.

Nigel · « **Reply #4 on:** January 10 2016, 23:31 »

Quote from: Baltic on January 10 2016, 22:34

... Basically that safeshoremarine "galvanic isolator" is not isolator at all..
Just some diodes on the earth wire...

Which is how they all work. Galvanic currents are around 500mV, depending on the metals involved; so a pair of diodes will block them, but allow a higher leakage voltage to trip the RCD.

dawntreader · « **Reply #5 on:** January 12 2016, 08:01 »

I fitted a galvanic isolator shortly after buying Dawn Treader in 2006. I only replaced the original anodes last Winter - they were still >50% original weight after 9 years of service but weakened at the mounting bolts. I had been on a marina mooring for over 5 years so I wholeheartedly recommend getting one.

landes_h · « **Reply #6 on:** January 12 2016, 09:44 »

Most electric equipment these days are insulated, i.e. no electric connection between outer case and any internal circuits. That's why they only have a 2pole plug (in Main Europe!). Of course it may be against relevant regulations, but it is very efficient to simply disconnect the earth wire (green/yellow) at the socket where landpower comes in. The problem is the current between the own ship and neighbouring ships. This is what eats up the anodes. The Galvanic Insulators do the same by means of two anti-parallel diodes and a capacitor across.

I never leave my boat plugged in when I go home, but most motor boats are plugged in because they have problems with water coming in and need an active bilge pump.
On my previous boat this problem was extrem, anodes were eaten in half a season. Finally I disconnected the ground wire and the problem was gone.
I shall not recommend this because it may violate some electrical safety rules, however it is efficient. After the Battery Charger all electrics are 12V DC. None of that should touch the engine body either. A boat is not a car, where all metal part are Minus. If everything is floating there is no current to neighbouring vessels or the landpower.
I hope I could tell it half way clear. Anyway once out the Harbour and unplugged this problems should not exist. If they still do exist, it is as mentioned above. There is some connection between Minus and engine block, or saildrive. It's all a bit mysterious, but as long as nothing is connected to each other it should be fine.

Ripster · « **Reply #7 on:** January 12 2016, 10:12 »

Quote from: Aquila on January 10 2016, 20:09

Hi all, looking to fit a galvanic isolator to my Bav 36 (2012), no real reason except I don't have one. I am fitting a new Darglow feather stream prop which costs a lot and I think this may help protect it. Would welcome any views before i buy one from safeshoremarine. thanks

I have one fitted on my 2011 36 - Safeshore I think and its been on since new. After experiences on MOBOs some years ago with Galvanic corrosion I wouldn't be without one in a Marina. Piece of cake to fit and if you get the remote lights gizmo - testable too. I am only down the pontoon from you, so if you need/want to see one in place - let me know.

Aquila · « **Reply #8 on:** January 13 2016, 10:06 »

Thanks everyone for your comments, this confirms my thoughts about the benefits of fitting an isolator. I have ordered one and awaiting delivery. Thank you forum.

MarkTheBike · « **Reply #9 on:** January 14 2016, 12:04 »

Quote from: Aquila on January 13 2016, 10:06

Thanks everyone for your comments, this confirms my thoughts about the benefits of fitting an isolator. I have ordered one and awaiting delivery. Thank you forum.

Hi Aquila
Please let us know which one you ordered and how easy to fit, etc. when you've got a few moments spare. I think it would be of interest to all who park in a marina and don't have one yet.
Cheers

Symphony · « **Reply #10 on:** January 14 2016, 22:46 »

I had a Zinc Saver from Force 4 fitted to my new boat. Mounted in the cockpit locker close to shorepower inlet. comes with full instructions. Not critical where it is located physically except it should be dry and accessible.

Kaptajnen · « **Reply #11 on:** January 15 2016, 15:48 »

There is a lot of confusion regarding this issue. While our Bavaria 38 was built in 2000 has no bonding as described below, current ABYC and European standards mandate this viz.

"THE PROBLEM:
Recent interest in damage done to boats due to the 230V shore mains has highlighted the need to fit a galvanic isolator to your boat.
In order for modern boat builders to comply with modern CE standards such as EN ISO 13297 they must fit the shore earth wire to your boats bonding system which is also connected to the hull / anodes / fuel tanks / engine blocks / shafts / propellers / stern tubes / rudders / rudder glands / water intakes / etc. This ensures that any 230V mains faults will operate the R.C.D on the boat in order to save your life.
The down side of these standards is that electrically speaking your boat is now connected to the rest of the boats in the marina and any other metal structures in the area. Electrically speaking they become one and the same. If you follow the earth line you can see everything bonded to the earth, this includes your boat, the one next to you, metal work etc.
This results in two main problems.
1) Any earth problem on any boat or shore earth will increase the voltage in the common earth cable and dissolve - adversely affecting your boat by dissolving your anodes at an alarming rate (this could result in the total loss of all the metal on the boat below the waterline).

2) Because all the boats are now one, if you have a zinc anode on your boat, but the boat beside you does not or even worse, the marina has not put anodes on its structures (metal pontoons etc) then your boat's zinc, (or aluminium / magnesium) will protect all the structures and boats around you, resulting in dramatic zinc loss and expensive lift-outs to replace the zinc. For boats on inland waterways, if you have a magnesium anode and everyone else has zinc or no anodes at all, your magnesium anode will protect all.

THE SOLUTION:
The trick is to maintain the continuity with the earth to ensure the safety of your life but remove the continuity with the shore power for the safety of your boat. The solution is very simple. By installing a Galvanic Isolator / Zinc Saver we maintain a good earth link with the shore, but prevent any stray currents coming up the earth line and damaging the boat. The isolator is in theory a simple device but it has to be built to a stringent specification and tested by an independent test house to ensure they comply with the relevant standards, be it the less stringent CE standard or the more stringent American Boating and Yachting Council standard. This means in a major fault condition it can carry its rated current for 24 hours without exceeding 90 deg C on the heat sink. "

Nigel · « **Reply #12 on:** January 15 2016, 17:53 »

Quote from: Kaptajnen on January 15 2016, 15:48

... the shore earth wire to your boats bonding system which is also connected to the hull / anodes / fuel tanks / engine blocks / shafts / propellers / stern tubes / rudders / rudder glands / water intakes / etc. ...

Obviously quoted from a manufacturer of GIs. This is not a requirement in Europe, only that any mains connected equipment can be earthed if required.

I would certainly not bond mains earth to any of the above. Howeved, a GI is still a good idea if you regularly connect to shore power.

Impavidus · « **Reply #13 on:** January 17 2016, 17:21 »

Just to add more fuel to the fire..........

 6 Months in Port Solent hull anode gone! (See my post on Coppercoat, Strippers and Brunton). Fitted one of these;

https://www.marinesuperstore.com/electrical/battery-management/sterling-galvanic-isolator-zinc-saver-30a

Inspected the anodes today with my underwater CCTV on a pole, anodes still like new??..

Ant.

Nigel · « **Reply #14 on:** January 17 2016, 23:11 »

It may be of interest that a simple way to help protect the saildrive anode is to run a cable from a stud at the top to a rear locker, then hang an anode off this.

The Other Woman · « **Reply #15 on:** January 18 2016, 10:04 »

Hi All
I have just made a Galvanic isolator as shown in PBO seems to work on the bench cost £8.00 so will fit to the boat next weekend.
The link is https://www.hisse-et-oh.com/system/assets/000/065/859/original/Galvanic_Isolator.pdf?1358009981

Good luck
Mick

landes_h · « **Reply #16 on:** January 19 2016, 10:01 »

The DIY Isolator has one disadvantage. If for instance lightning strikes the electric System and the diodes are killed, you have no more grounding on the ship, but believe you still have. No indication !!
Just saying.....

CRYSTAL · « **Reply #17 on:** January 19 2016, 15:25 »

One stupid question to grasp this idea of RCD / earth:

To get zapped, you need to complete the cct via earth. No earth no return path to complete the cct. Without earth, will the rcd still work as it only measures the current differecial and any difference it'll trip. At least that's what the test button does on the rcd.

MarkTheBike · « **Reply #18 on:** January 20 2016, 10:33 »

Not a stupid question at all! I guess the breakers are only there BECAUSE of the earth and if it's missing then there's no need for one. Is that right?

CRYSTAL · « **Reply #19 on:** January 20 2016, 14:45 »

Depends on which breaker. Cct breakers non rcd are for overload ie 16A should cut off at its specified rating within few hundred ms before things start to smoke.

Rcd will / should protect you with the slightest current differecial.

I heard there are electronic engineering professors who own boats are also contemplating the earth connection. Basically cut it off.

landes_h · « **Reply #20 on:** January 21 2016, 11:11 »

Quote from: CRYSTAL on January 20 2016, 14:45

I heard there are electronic engineering professors who own boats are also contemplating the earth connection. Basically cut it off.

....my saying, and I'm not a professor, just electronic engineer.

Salty · « **Reply #21 on:** March 27 2016, 11:31 »

On my B36(2002), the rigging is attached to the mast with metal fittings, and the mast is earthed by metal to metal contact where it is stepped through to the keel. The keel is possibly somewhat insulated from the sea water by being painted with antifouling. Also the only rigging that someone with wet feet on the swimming or boarding ladder could reach is that of the lower end of the divided backstay, and that runs through a single sheave block with a plastic (insulating ?) sheave at the upper part, while being connected to eye bolts secured to the GRP transom which is a non-conductor. They could also just as easily take a hold of the grab rails placed there specifically to help persons boarding there but which are bolted to the GRP transom instead of holding the rigging. Arguably possible I suppose for an electric current to be present, but I think also arguably rather unlikely.
For a disinterested passing swimmer with no reason to want to touch the boat I'm hard pushed to think there could be a risk of electrocution, and if there was then someone with a better and more knowledgeable understanding of the risks involved than myself would hopefully have raised public awareness and legislation regarding boat electrical systems would then surely follow.
I do wonder if the tale of the killed swimmer is nothing more than fiction where if sufficient people repeat it often enough it then morphs it way into fact.

Aquila · « **Reply #22 on:** June 08 2016, 09:06 »

Quick update, I fitted the galvanic isolator from safeshore marine, very easy to fit alongside main RCD switch box. On my boat the earth lead never actually went through the electrical intake box and just went around so all I needed to do was cut the earth and attach to isolator I mounted next to it. I did a test once fitted as suggested but Safeshore marine using my meter.

I never bothered to buy the unit with the remote status switch as its not a problem to look at it when I need to. Can't see how effective it is as yet until end of year out but for the money it was worth adding. Will keep you posted.

Aquila · « **Reply #23 on:** January 17 2017, 11:16 »

Quick update since I installed my Safemarine Galvanic Isolator a year ago. Got Aquila lifted and well pleased with anodes, all anodes showed little wear and tear except the bow thruster which looked pretty normal. In summary I am pleased I installed the isolator.

Kibo · « **Reply #24 on:** January 17 2017, 17:12 »

Quote from: Salty on March 27 2016, 11:31

On my B36(2002), the rigging is attached to the mast with metal fittings, and the mast is earthed by metal to metal contact where it is stepped through to the keel. The keel is possibly somewhat insulated from the sea water by being painted with antifouling. Also the only rigging that someone with wet feet on the swimming or boarding ladder could reach is that of the lower end of the divided backstay, and that runs through a single sheave block with a plastic (insulating ?) sheave at the upper part, while being connected to eye bolts secured to the GRP transom which is a non-conductor. They could also just as easily take a hold of the grab rails placed there specifically to help persons boarding there but which are bolted to the GRP transom instead of holding the rigging. Arguably possible I suppose for an electric current to be present, but I think also arguably rather unlikely.
For a disinterested passing swimmer with no reason to want to touch the boat I'm hard pushed to think there could be a risk of electrocution, and if there was then someone with a better and more knowledgeable understanding of the risks involved than myself would hopefully have raised public awareness and legislation regarding boat electrical systems would then surely follow.
I do wonder if the tale of the killed swimmer is nothing more than fiction where if sufficient people repeat it often enough it then morphs it way into fact.

Its not a myth. It happens in fresh water.
http://www.boatus.com/seaworthy/magazine/2013/july/electric-shock-drowning-explained.asp