Galvanic isolators

[MalcolmP]

This is a new thread based on a branch that developed from:

jeanneau.proboards.com/thread/3457/electrolysis-bracket?page=1&scrollTo=18456


jeanneau.proboards.com/post/18454


jeanneau.proboards.com/post/18456


jeanneau.proboards.com/post/18457


jeanneau.proboards.com/post/18458


jeanneau.proboards.com/post/18460


jeanneau.proboards.com/post/18463

[MalcolmP]

I found this interesting article after following a link from another current thread on batteries and Smart Gauges which seems to give an unbiased view on the pros and cons of Galvanic Isolators v Isolation Transformers



www.smartgauge.co.uk/galv_tran.html

[alex1949]

To sailbleu :

The only place I know to install the galvanic isolator would be on the EARTH (yellow/green) line coming from the shore power connection anyplace before the EARTH line is getting connected to any part on board.

As mentioned before we want to block ingoing or outgoing law currents on this line but still allowing earthling capability for major currents if needed. Keep in mind, this EARTH line on any marina is actually connected to sea water through foundation metal rods.

Perfect solution would have been if all boats and marina system will use this system at all time.

And finally, GALVANIC ISOLLETORS are sometimes called also ANODE/ZINC SAVERS it is to say we will always need our anode/zinc to protect, the galvanic isolator will slow zinc eating dramatically ,this is their only job.

Alex

[sailbleu]

Good start Alex , and Malcolm of course.
Lets hope more posters chip in , would love the learn more on the subject as my situation has changed somewhat . Practically living aboard so to speak.
What did you guys think about the DIY isolator found in the link on the P-bracket topic ?

Regards

[Trevor]

Hello Sailbleu,

In Australia, any device that is used as a part of the mains power electrical circuitry, must be certified for use and comply with the Australian standards. Prior to certification it has to undergo testing to ensure to is compliant and then can carry Australian/New Zealand certification.

One of the issues relating to permanently wired earth components is that of the capacity to carry momentary "fault currents". The fault current commercial Galvanic isolators can carry is very high ( 5000 amps, but only for a few milliseconds) and the constant current carrying capacity of the one I installed on my boat is 67 amps. I know that is unreasonably high, but this is in the safety circuit of the boat so needs to be absolutely robust and not subject to failure because if it fails, it renders the boat dangerous and the owner may not know. The device must be able to handle the fault current for long enough for the protection circuitry to act.

That is why some galvanic isolator manuals recommend annual testing to ensure it is still working. If it doesn't work it is like removing the earth wire from the boat.....not good. The one I installed has what is called a "failsafe" design meaning if the device failed it would still conduct so it would never render the device open circuit, the greatest fear of no earth on the boat.

The capacitor you have previously mentioned helps bypass the diodes for harmonic currents generated by modern switch mode power supplies. This capacitor does need to carry some current and the size of the capacitor needs to be large enough to carry low frequencies but does not need to be high voltage rated as the only voltage that could be developed across the capacitor is the forward bias voltage of two diodes ( about 1.2Volts).

For the reasons I mentioned above I decided to purchase a commercially available unit instead of simply putting a diode bridge on a heatsink and installing that. If the electrical integrity of the boat is not in accordance with Australian standards, insurance is void so I would rather not take the risk in any case.

I toyed with the idea of manufacturing these devices once so I spent way too much time researching the characteristics of the devices.  

Regards

[so36idavid]

Trevor,

ABYC requires that galvanic isolators either fail safe (ground circuit closed) or have a remote monitor which will signal a fault if the isolator fails. Pretty much any product you can buy will be one of these, at least the products that I've seen in the US. You're not required to install the monitor, but it does seem like a good idea.

FYI I installed one of these and it turned my "zinc a month" habit into a "two zincs a year" habit . 

David

[sailbleu]

Not out of the woods yet.
Ok , I will buy a decent isolator that has all the required features , but where do I connect it to ?
I know as close to the shore earth as possible , but where do I connect the other lead ?
I mentioned before of doing it on the engine , but i guess that will not work as my engine is completely separated from any batterie current be it minus or plus .
Dont know the exact frase , but it is neutral.
Do I connect the lead to the hull ? My boat is not made of steel , wont work.

Suggestiona anyone ?
Thanks
Regards

[alex1949]

As  mentioned before, you apply the galvanic isolator on the earth line that comes from the 220/110 volt shore power (usually yellow/green cord) .Anywhere on a convenient place but important ! before this line get spliced/connected to anything on board. Just cut the earth line and connect the two side pieces into the isolator's terminals. usually, this earth line ends on a connection to your engine block ,you block this line in & out by using the isolator.

btw the US regulations allow only galvanic isolators with the automatic indicator that will alert any problem on the unit. The European regulations does not force it and that why you can buy those simple cheap isolators from decent producers like Sterling UK.

Alex

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[alex1949]

To get a brighter picture for European zone boaters please go to Sterling power UK and look for Zinc Savers.

sterling-power.com/

[sailbleu]

Alex,

I think I now have the picture.
After reading the Sterling explanation , I understand what it's all about.
Will buy a device very soon now and install it when I get back to the boat in january.
In the meantime I will - as I always do - disconnect the AC power when not staying on the boat.

Thanks

[optimystic]

I plan on adding a galvanic isolator this month. It seems like this item should be standard equipment on all jeanneau boats. Im wonderng why it isn't just a standard like putting on a zink. I just replaced my first saildrive zink. $80 and it only lasted July to November. 

[alex1949]

Hi Optimystic,

That is why those galvanic isolators are called commercially  ZINC SAVERS.

Read the Sterling Uk web (see some posts before).

Do not expect no zinc eating after installing it, but do expect a dramatic slowdown and much less annual expense though.

Have a nice day

Alex

[optimystic]

I had the boat and slip tested and all readins were perfect. The electricians comment regarding the boat wiring was that they did a very nice job isolating systems. He tested all ac and dc vessel systems and shore power he also used both the saildrive and a thru hull (seperately tests) for grounding. I'm very satisfied with results. No need for adding any equipment. 

[sailbleu]

But isn't a galvanic isolator just there to protect your boat from boats with dodgy electrical wiring ?

Regards

[alex1949]

Sailblue is right !!

You measured now, but a while letter somebody nearby just start contributing  currents into the water and all tests with perfect results vanishes.

You need a permanent preventer.

Alex

[electricmonk]

Dec 13, 2014 2:29:54 GMT optimystic said:

I had the boat and slip tested and all readins were perfect. The electricians comment regarding the boat wiring was that they did a very nice job isolating systems. He tested all ac and dc vessel systems and shore power he also used both the saildrive and a thru hull (seperately tests) for grounding. I'm very satisfied with results. No need for adding any equipment. 

Good so your boat has no faults - but what about the boat next door? what about the earth on the dock supply? The galvanic isolator protects your boat from THEIR faults.

[optimystic]

The dock ac was also tested and delivered good results. I'll install an isolater after the boat show in January but wanted to get a true baseline for our moorage. I have new zink and wanted to make sure that I understand the starting point for corrosion. If no testing was done I wouldn't have an understanding on the boat,marina or other boats. The most important part was testing every system on our 379. Installing an isolator is the result because it is preventative but I believe testing should be done first since if there was a problem I know where it is. Also this test measured the zink and showed that we have enough zink for protection and have no need to add additional zink. All good information. Thanks for the input. It is all very helpful. 

[hoppy]

Another thread here got me wondering. Is there any point to a galvanic isolator if your boat is only connected to shore power in the marina for only a few weeks a year?

[rxc]

I think one needs some sort of protection from miswiring, no matter how little time one is plugged into shore power. Galvanic corrosion can be destructive very quickly (in a matter of days, if the connections are really bad), and then there is the safety issue. I have an isolation transformer on my boat, not an isolater, and I consider it to be money well spent. We have a friend with a Hunter, and it was delivered with an isolation transformer, so some boat builders seem to have decided that it is important enough to install straight from the factory.

[ianqv]

Hi All,

We are plugged in to the mains at the marina 24/7.
Last year we fitted a galvanic isolator. My only regret.... why we didn't do this years ago!
Every year my propshaft anode is almost totally eaten away, in fact two years ago it came loose on the shaft on our last trip out (this was because it had just been eaten away to almost nothing).
Fitted the isolator at the beginning of this season and the anodes aren't even half worn!
And no it's not because we now have a dodgey earth - its because everyone else (inc the marina) is not nibbling away at our anodes now.

Best Regards

Ian

[On y va]

When I leave my boat for longer periods, I unplug actually as I do not want to have the battery charger on all the time. It is one of the biggest causers of fires on boats. My solar panel keeps the batteries full anyway in my absence.

I have a "portable" (although I have permanently fixed it) galvanic isolator installed. I have commented about this unit in another thread. It is the most simple way of installing a galvanic isolator and it has warming lights for both AC and DC faults.

This is the unit: www.safeshoremarine.com/Inline%20isolator.htm

How simple do you want it??

(and no, I do not have shares in this company!!  )

[hoppy]

Jan 3, 2015 20:33:55 GMT On y va said:

When I leave my boat for longer periods, I unplug actually as I do not want to have the battery charger on all the time. It is one of the biggest causers of fires on boats. My solar panel keeps the batteries full anyway in my absence.

I have a "portable" (although I have permanently fixed it) galvanic isolator installed. I have commented about this unit in another thread. It is the most simple way of installing a galvanic isolator and it has warming lights for both AC and DC faults.

This is the unit: www.safeshoremarine.com/Inline%20isolator.htm

How simple do you want it??

(and no, I do not have shares in this company!!  )

and I hope you also do not do the web design for that company either

[On y va]

hoppy, have you seen the video about the 30 second plug and play!! 

(sorry, off-topic)

[hoppy]

Jan 4, 2015 13:03:57 GMT On y va said:

hoppy, have you seen the video about the 30 second plug and play!! 

(sorry, off-topic)

Yeah... It's such a simple thing to do that they could not be bothered filming someone doing it

Years ago that sort of site design would have given me a "red flag" signal that it is either a dodgy product or scam site. Now I know it is not, because a scam artist would make much more of an effort on the web design

[hoppy]

For the normal style of G.I. where do you mount it? Close to the shore power connector or perhaps behind the switch panel where the shore power connects to the boats electrics ?