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Old 28-01-2012, 08:29   #1
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Galvanic Isolator or Iso Transformer - To Bond or Not ?

I have a 43 ft Bene and am looking for opinions on the above. I am leaning towards the galv isolator due to price, size, and weight considerations, but have no experience with this. I have bronze thru-hulls for the most part which are not currently bonded. The only zinc is on the prop shaft and I do not have a genset or inverter. Thanks.
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Old 28-01-2012, 08:34   #2
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Re: Galvanic Isolator or Iso Transformer? To Bond or not?

Galvanic isolators can fail and leave you without a ground on board - a potentially fatal problem. Or fail closed and fail to protect your boat.

I think the isolation transformer is a much better solution, but much more expensive, heavier, and bulkier, plus will limit the amount of current from shore power.

There is a third solution -- just don't leave the boat plugged in. Have you thought about that? If you have solar or a wind gennie, why leave your boat plugged in when you're not on board? That might be the best solution of all.
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Old 28-01-2012, 09:30   #3
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Re: Galvanic Isolator or Iso Transformer? To Bond or not?

Here’s a good analysis of GI’s & IT’s:
SmartGauge Electronics - Isolation Transformers or Galvanic Isolator? 1/2
SmartGauge Electronics - Isolation Transformers or Galvanic Isolator 2/2

About Fail-Safe GI’s - Excerpted from ABYC A-8
“Fail Safe Galvanic Isolator – An isolator that, if after meeting all other criteria of this standard, meets the requirements of an effective ground-fault current path when subjected to the test conditions in A-28.14, Table 2.
NOTE: The device may not continue to provide galvanic isolation in the event of a failure. “

“28.6.1 The galvanic isolator shall be equipped with an integral or external status monitor that provides an audible or visible indication of failure.
Exception: Fail-Safe galvanic isolators
28.6.2 The monitor shall alert when tested between the wiring terminals on the isolator as a result of the following conditions:
28.6.2.1 the isolator fails to conduct above 2.5 volts DC in both directions or if the isolator fails to open below 1.0 volt DC in both directions, or
28.6.2.2 the shorted or open condition of current carrying components in the ground path.

More ➥ http://deimarine.com/deimarine/sites..._liability.pdf
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Old 28-01-2012, 09:44   #4
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Re: Galvanic Isolator or Iso Transformer? To Bond or not?

Thanks for the quick replies. I read through the above links already as well as the ABYC section 11 standards - well I am on page 50 or so. I already do not have the shore power connected while I am away from the boat and have a wind generator on board. In fact, the boat is currently in the yard on stands. I recently purchased the boat and am trying to balance the ABYC ideals with reality. I never want to be the one responsible for unsafe conditions which could injure someone. I will likely leave things be for now and go with the isolation transformer when the time comes when I need shore power for an extended period. I am actually looking for folks who have this equipment in a similar vessel. I am not sure where I would install an IT. It looks like they mostly mount to a bulkhead, but thats a lot of weight! The shore power inlet is on the aft starboard cabin bulkhead just above the panel in the aft starboard berth. Installing an IT there looks feasible, but would certainly infringe on space and likely generate some heat. A galvanic isolator with an indicator might be a reasonable alternative. What about the bonding question?
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Old 28-01-2012, 09:56   #5
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Re: Galvanic Isolator or Iso Transformer? To Bond or not?

Quote:
Originally Posted by CHM View Post
What about the bonding question?
I have a Bene 473 According to dealer, the boat was originally delivered with only a prop zinc, which accordding to him last about 3 months

The PO fitted a hull anode, and I have also fitted a shaft anode. Also in the process of fitting bushes to the prop shaft, which will then connect direct to the hull anode. Although the prop shaft has a solid coupling to the gear box, I have been advised that continuity can be lost with the shaft turning, the oil in the gear box isolating the prop shaft.
As for the through hulls, only two on my boat are bonded, the cooling water">engine cooling water inlet, and the water inlet to the prop shaft seal This was factory fitted.
Boat is 10 yrs old with no sign of corrosion on the though hulls.

If your concerned, best get a boat electrician to check the boat over when back in the water.

Oh, and +1 to disconnecting from shore power when not needed
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Old 28-01-2012, 10:59   #6
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Re: Galvanic Isolator or Iso Transformer? To Bond or not?

If you're in fresh water and worried about safety, forget the galvanic isolator. Install one of these

Double Pole Residual Current Circuit Breaker ( RCBO-ELCI )

Then break the connection between the AC green wire and the boat DC ground which is the reason you need a galvanic isolater in first place.
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Old 28-01-2012, 11:09   #7
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Re: Galvanic Isolator or Iso Transformer? To Bond or not?

The one you referenced and E-02 all say IF bonding, IF cathodic protection, IF galvanic isolator, IF isolation transformer, is installed...

So these are not ABYC requirements. Not saying that these are bad or good ideas, just if you're worried about following the standard, the standard does not require any of the above.

John

Quote:
Originally Posted by CHM View Post
Thanks for the quick replies. I read through the above links already as well as the ABYC section 11 standards - well I am on page 50 or so. I already do not have the shore power connected while I am away from the boat and have a wind generator on board. In fact, the boat is currently in the yard on stands. I recently purchased the boat and am trying to balance the ABYC ideals with reality. I never want to be the one responsible for unsafe conditions which could injure someone. I will likely leave things be for now and go with the isolation transformer when the time comes when I need shore power for an extended period. I am actually looking for folks who have this equipment in a similar vessel. I am not sure where I would install an IT. It looks like they mostly mount to a bulkhead, but thats a lot of weight! The shore power inlet is on the aft starboard cabin bulkhead just above the panel in the aft starboard berth. Installing an IT there looks feasible, but would certainly infringe on space and likely generate some heat. A galvanic isolator with an indicator might be a reasonable alternative. What about the bonding question?
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Old 29-01-2012, 09:22   #8
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Re: Galvanic Isolator or Iso Transformer? To Bond or not?

Quote:
Originally Posted by Dockhead View Post
Galvanic isolators can fail and leave you without a ground on board - a potentially fatal problem. Or fail closed and fail to protect your boat.
We have sold thousands of Galvanic Isolators over a period of about 14 years. EVERY one has unconditonal warranty. So far there has only been one return under warranty and it was a severe lightning strike victim.

Certainly an isolation transformer is preferable especially if you get one with voltage taps. On our boat we use shore power anywhere from about 80 volts to 430. But there is too much paranoia on the reliability of galvanic isolators, they are extremely reliable.
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Old 29-01-2012, 11:38   #9
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Re: Galvanic Isolator or Iso Transformer? To Bond or not?

But without a remote monitor you don't know if it has failed or not.
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Old 29-01-2012, 11:42   #10
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Re: Galvanic Isolator or Iso Transformer? To Bond or not?

The standard European method is as seen in the Beneteau, thats is no continuous bonding, hence a galvanic isolator or even a traffo isnt as common as in US systems, with continous bonding.

I wouldnt install either just check the thru-hulls as in Europe DNZ brass is more common then bronze and thats whats youll have.
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Old 29-01-2012, 11:49   #11
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Re: Galvanic Isolator or Iso Transformer? To Bond or not?

My boat doesn't have a galvanic isolator, yet, but if it had I probably wouldn't have gotten my lights knocked out a few days ago. My shore power breaker is in the back underneath the hatch in the cockpit. I had to lean over in there to get something and my head touched it lighting me up good. I found out the third ground wire isn't even there between the shore power inlet and breaker so I became the ground. This is my project this week. The surveyor completely missed it all too. Make sure you have good grounds! At least now I know why my shaft zinc last so long.
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Old 29-01-2012, 14:27   #12
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Re: Galvanic Isolator or Iso Transformer? To Bond or not?

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Originally Posted by mitiempo View Post
But without a remote monitor you don't know if it has failed or not.
That is very true from a theoretical "liabilility for ABYC" standpoint but look at the practical side of owning a boat. If you are sufficiently paranoid and have money to burn there are hundreds of things on a boat you can monitor. But in the practical world you allocate your budget on itmes with the highest ROI.

To meet the full requirements of the ABYC monitoring specification it would double the cost of the isolator. Especially considering the requirement of a "Remote monitor visible to the boat operator" DUH you don't use shore power when operating a boat.

So if you are going to spend $100 on monitoring something I can think of dozens of things much more important than a galvanic isolator. How about a raw water exit temperature? A second level bilge alarm? A remote indicator on Racor filter pressure?

Considering we have had one failure in over 2,000 isolators in 14 years that calculates to a life expectancy of 1 failure every 28,000 years. I know that figure is meaningless due to insufficient data but you get the message.

Spend your monitoring dollars where they are practical and NEEDED and not to allay the paranoia of ABYC who only require it so they can't be sued if it fails and they didn't require it.
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Old 01-02-2012, 08:20   #13
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Re: Galvanic Isolator or Iso Transformer? To Bond or not?

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Spend your monitoring dollars where they are practical and NEEDED and not to allay the paranoia of ABYC who only require it so they can't be sued if it fails and they didn't require it.
As a member of two of the committees that write the Standards, this comment (emphasis added) is the author's opinion and, not what the ABYC is about.

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Old 01-02-2012, 08:34   #14
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Re: Galvanic Isolator or Iso Transformer? To Bond or not?

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As a member of two of the committees that write the Standards, this comment (emphasis added) is the author's opinion and, not what the ABYC is about.

Charlie
Oh I understand and agree fully, Charlie, and the work ABYC does is very valuable. But it seems to be the "bible" and written to cover all contingencies. I fear the motives are often influenced by the real paranoia of being sued if someone died because ABYC forgot to require a monitor.

From a real life practical approach, I stick by my statement that unless you have unlimited funds you should budget them where they will give the best return on investment.

Many of us rely on a "bible" to guide our life but very few follow it to the letter. I applaud the standards and having a reference is of great value but each individual can decide what to incorporate and what to wish for.

Spending $100 to monitor a component with a MTBF of over 1,000 years compared to things like navigation and safety is sometimes hard to justify.
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Old 01-02-2012, 09:00   #15
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Re: Galvanic Isolator or Iso Transformer? To Bond or not?

You should buy and install an IT. An IT is *much* safer because it is in fact a safety device that not only protects the boat but also the people.

A GI is a device that *tries* to protect the boat while *trying* not to lower the safety of people aboard too much.

Also, when an IT fails you loose power. When a GI fails you loose protection.

I don't think it's wise to ridicule safety provisions that are there to guard against possible failures of GI. Especially not when you sell GI's and thus depend on them for your livelihood... although, after selling thousands of them that shouldn't matter much anymore.

ciao!
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