Where to locate Galvanic Isolator

[Oceansailor]

Originally Posted by Ahmet Erkan

Dear Oceansailor,
The short answer is, a properly installed isolation transformer on board a vessel does not protect the boat. The improper advice given by “experts” on this forum to disconnect the shore power ground from the hull ground (because the transformer through some magic makes everything safe) actually will protect the boat but at the price of endangering the swimmers or divers near the boat.

1. A fail safe galvanic isolator will always protect the swimmers and with a properly designed power system monitor it will also guarantee the boat is protected as well.
2. A dock mounted isolation transformer with an onboard properly designed power system monitor will also protect the boat and protect the swimmers. NOTE: The shorepower grounding conductor is still required to be brought onboard for the power system monitor to test and verify isolation and that the system has no single point failures for the swimmers protection.

Fellow Ocean Sailor,
I have defended items 1 and 2 above based on sound electrical principles but I have also been raised with values from a culture which considers bragging, chest beating etc as inferior forms of behavior. Therefore, if you are not a marine power systems expert and if you are going to believe me only if I have at least the same academic credentials and work experience as the other experts on this forum, feel free to contact me privately.
Lastly, experts in this forum should not recommend improper wiring of isolation transformers and ABYC should consider phasing out the older wiring diagrams in E11 which show no connection between the shore power grounding conductor and the underwater metals of the vessel. In fact if I am not mistaken the current technical committee at ABYC state they are not responsible for some of the figures in the documents that were introduced by the original technical management. Also ABYC states they are not the law, but recommendations and guidelines. Excellent and prudent guidelines I must admit except for a few legacy figures that their time has passed and they should be revised out.
Cheers mate
Ahmet (ahmet_erkan@sss-nc.com)

Please explain how a a fail safe galvanic isolator protects people better than if the boat was not equipped with a galvanic isolator?

[Sailorlou]

Originally Posted by Oceansailor

Could we not agree that a galvanic isolator only protects the boat.

An isolation transformer protects boat even better and in addition also protects people?

Oceansailor,

You are basically correct in your statement. Although having a shore ground connection which is required in the installation of a galvanic isolator is a basic protection as long as it is not compromised.

I think there is only one person on this forum that would disagree.

[DotDun]

Originally Posted by Ahmet Erkan

Dear Oceansailor,
The short answer is, a properly installed isolation transformer on board a vessel does not protect the boat. The improper advice given by “experts” on this forum to disconnect the shore power ground from the hull ground (because the transformer through some magic makes everything safe) actually will protect the boat but at the price of endangering the swimmers or divers near the boat.

1. A fail safe galvanic isolator will always protect the swimmers and with a properly designed power system monitor it will also guarantee the boat is protected as well.
2. A dock mounted isolation transformer with an onboard properly designed power system monitor will also protect the boat and protect the swimmers. NOTE: The shorepower grounding conductor is still required to be brought onboard for the power system monitor to test and verify isolation and that the system has no single point failures for the swimmers protection.

Fellow Ocean Sailor,
I have defended items 1 and 2 above based on sound electrical principles but I have also been raised with values from a culture which considers bragging, chest beating etc as inferior forms of behavior. Therefore, if you are not a marine power systems expert and if you are going to believe me only if I have at least the same academic credentials and work experience as the other experts on this forum, feel free to contact me privately.
Lastly, experts in this forum should not recommend improper wiring of isolation transformers and ABYC should consider phasing out the older wiring diagrams in E11 which show no connection between the shore power grounding conductor and the underwater metals of the vessel. In fact if I am not mistaken the current technical committee at ABYC state they are not responsible for some of the figures in the documents that were introduced by the original technical management. Also ABYC states they are not the law, but recommendations and guidelines. Excellent and prudent guidelines I must admit except for a few legacy figures that their time has passed and they should be revised out.
Cheers mate
Ahmet (ahmet_erkan@sss-nc.com)

Until you understand the principles around source and ground return paths, you will not understand why a properly installed isolation transformer is the best protection for both the boat and swimmers around the boat.

[Pelagic]

[QUOTE=Ahmet Erkan;2658813]

.....Lastly, experts in this forum should not recommend improper wiring of isolation transformers and ABYC should consider phasing out the older wiring diagrams in E11 which show no connection between the shore power grounding conductor and the underwater metals of the vessel. QUOTE]

Hi Ahmet,
Just to clarify:

Are you saying that the Dutch manufacturer Victron, who makes my 7000w isolation transfer have published wrong wiring drawings and instructions for their customers in thier Installation and Operation Manual?

Here are the two drawings

The first when the yacht is IN the water explains that unless you install a jumper J5-J7, the system is "floating"
Attachment 172325

And the 2nd, when drydocked where you are advised to bypass the ground isolation with a provided jumper.

Attachment 172326

My limited understanding of this is..... in case you are having any welding done while drydocked. But maybe there are other reasons.

Just trying to understand.

[Ahmet Erkan]

[QUOTE=Pelagic;2658859]

Originally Posted by Ahmet Erkan

.....Lastly, experts in this forum should not recommend improper wiring of isolation transformers and ABYC should consider phasing out the older wiring diagrams in E11 which show no connection between the shore power grounding conductor and the underwater metals of the vessel. QUOTE]

Hi Ahmet,
Just to clarify:

Are you saying that the Dutch manufacturer Victron, who makes my 7000w isolation transfer have published wrong wiring drawings and instructions for their customers in thier Installation and Operation Manual?

Here are the two drawings

The first when the yacht is IN the water explains that unless you install a jumper J5-J7, the system is "floating"
Attachment 172325

And the 2nd, when drydocked where you are advised to bypass the ground isolation with a provided jumper.

Attachment 172326

My limited understanding of this is..... in case you are having any welding done while drydocked. But maybe there are other reasons.

Just trying to understand.

Sorry,
I could not open the attachments. Please resend.

By the way, electrons don't know the difference between Dutch, English, French, Italian etc manufacturers. Electrons will do what they want to do.
Having said that, I read a blog long time ago, I think it was written by the owner of Victron. The blog was very informative and the author seemed to be a very clever and learned fellow.

[Pelagic]

Resend

[Ahmet Erkan]

Originally Posted by DotDun

Until you understand the principles around source and ground return paths, you will not understand why a properly installed isolation transformer is the best protection for both the boat and swimmers around the boat.

I agree, one needs to understand "the principles around source and ground return paths" as well as work very hard, never stop learning, listen to people even if they are teaching something you already know etc etc and then understand maybe a thousand or so other things before becoming so arrogantly sure of what he or she is saying.

Thank you for the reminder Dot :-)

[Sailorlou]

Originally Posted by Ahmet Erkan

I agree, one needs to understand "the principles around source and ground return paths" as well as work very hard, never stop learning, listen to people even if they are teaching something you already know etc etc and then understand maybe a thousand or so other things before becoming so arrogantly sure of what he or she is saying.

Thank you for the reminder Dot :-)

So Ahmet,

Does this mean you agree with DotDun's statement?

[Sailorlou]

Originally Posted by Pelagic

Resend
Attachment 172331
Attachment 172332

Your drawings are correct.

When the boat is in the water (floating) and your source is the transformer, you have to have neutral connected to ground on the output side of the transformer.
AC electrical systems require that you have only one neutral to ground connection. That neutral is usually provided by the source. In this case the source is the transformer.

If your source is a direct connection from the marina (with no isolation transformer) the marina provides the neutral to ground connection and you do not connect neutral to ground aboard the boat. This is also true if you are using a galvanic isolator.

When you haul your boat out of the water the transformer is not required. The drawing you have for out of the water connection basically defeats the transformer and uses the shore power neutral to ground connection by connecting shore ground to ships ground.

[Ahmet Erkan]

Originally Posted by Pelagic

Resend
Attachment 172331
Attachment 172332

OK Pelagic,

I don't see a schematic or wiring diagram but here are my thoughts.
Your manual (I think) wants you to connect the "shore power grounding conductor" to the "underwater metals" (ie: The secondary Neutral, core, transformer case, underwater metals and shore power grounding conductor all connected together ???) when the boat is out of the water for safety reasons. This made me think that the manufacturer recommended changing the wiring to a conventional method to achieve safety when the boat transitioned from sea water to air. Here lies the answer, transitioning from seawater to freshwater is also a huge reduction in conductivity.
I would be very worried if I were you especially if your boat was in freshwater and a nine year old boy was playing in the water near your boat.

I think it is irresponsible to say people should not swim in a marina near a boats. It gets hot in summer and boats have swim platforms. Besides someone needs to clean the slime from the bottom of the boat, check the zincs etc. just like people working on your boat in the boatyard when the boat is out of the water.

I recommend installing a galvanic isolator between the two terminals Victron wants you to jumper when the boat is out of water and leave it there after splashing back into the water.
A properly designed power system monitor along with the galvanic isolator will protect against corrosion just as good as "actually even better" corrosion protection for the boat compared to taking the risk or killing people energizing a mis-wired isolation transformer with the grounds disconnected.

OK this is enough typing for today, my wife wants to drive downtown Wilmington to the Greek Festival. Be safe out there.

Ahmet

[Ahmet Erkan]

Originally Posted by Sailorlou

So Ahmet,

Does this mean you agree with DotDun's statement?

I agreed with DotDun that understanding things thoroughly is a requirement before talking big :-)
I was also impressed with the huge number of posts he has made in CF. Wow.
OK Sailorlou, I am going to partake on some Greek foods and maybe have a little Ouzo for the afternoon. Had enough of your silly transformers today :-)
Take care.

Cheers
Ahmet

[DotDun]

Originally Posted by Ahmet Erkan

OK Pelagic,

I don't see a schematic or wiring diagram but here are my thoughts.
Your manual (I think) wants you to connect the "shore power grounding conductor" to the "underwater metals" (ie: The secondary Neutral, core, transformer case, underwater metals and shore power grounding conductor all connected together ???) when the boat is out of the water for safety reasons. This made me think that the manufacturer recommended changing the wiring to a conventional method to achieve safety when the boat transitioned from sea water to air. Here lies the answer, transitioning from seawater to freshwater is also a huge reduction in conductivity.
I would be very worried if I were you especially if your boat was in freshwater and a nine year old boy was playing in the water near your boat.

I think it is irresponsible to say people should not swim in a marina near a boats. It gets hot in summer and boats have swim platforms. Besides someone needs to clean the slime from the bottom of the boat, check the zincs etc. just like people working on your boat in the boatyard when the boat is out of the water.

I recommend installing a galvanic isolator between the two terminals Victron wants you to jumper when the boat is out of water and leave it there after splashing back into the water.
A properly designed power system monitor along with the galvanic isolator will protect against corrosion just as good as "actually even better" corrosion protection for the boat compared to taking the risk or killing people energizing a mis-wired isolation transformer with the grounds disconnected.

OK this is enough typing for today, my wife wants to drive downtown Wilmington to the Greek Festival. Be safe out there.

Ahmet

Ahmet,

You are confused. An isolation transformer on a boat is a new power source. Since the shorepower doesn't go past the isolation transformer, there is no need to connect the shorepower ground to the boat ground, in fact it is detrimental to the boat to do so. The recommendation is to ground one side of the isolation transformer secondary to the boat ground (creating a neutral). Swimmers are safe as there is no return to shorepower source since it's 'isolated' at the transformer.

[Sailorlou]

Originally Posted by DotDun

Ahmet,

You are confused. An isolation transformer on a boat is a new power source. Since the shorepower doesn't go past the isolation transformer, there is no need to connect the shorepower ground to the boat ground, in fact it is detrimental to the boat to do so. The recommendation is to ground one side of the isolation transformer secondary to the boat ground (creating a neutral). Swimmers are safe as there is no return to shorepower source since it's 'isolated' at the transformer.

DotDun,

You are correct.

After all this discussion there seems to be no way to convince Ahmet Erkin that is he has a basic misunderstanding as to the functions and proper wiring of an isolation transformer or for that matter basic safety marine wiring technics.

I would advise all people reading this forum NOT to take Ahmet's recommendations and to instead talk with the experts in the field or better yet, take one of ABYC's classes on "Electro-Guard Marine Corrosion Solutions."

Saying it is safe to swim around marinas is grossly irresponsible. Even if your boat is properly protected that does not guarantee that other boats in the marina are safe or that the marina wiring is safe. Especially when in fresh water.

The ELECTRIC SHOCK DROWNING PREVENTION ASSOCIATION (ESDPA) "...strongly recommends no swimming or entry into the water whatsoever within 150 feet of any electrical source on the water, in the water, or at the water’s edge."

I urge everyone reading this thread to watch the video in the link below all the way through to it's end.

https://www.youtube.com/watch?v=7ndt7LGgAF8

Also, take a look at BoastUS's "Electric Shock Drowning Resource Center" for more information. Electric Shock Drowning Resource Center - Seaworthy - BoatUS

[dkenny64]

been trying to follow, learn and understand the isolation transformer part

of this thread.. I understand what they do and why..
what I don't get is why connect the secondary(output side) of the isolation transformer to any of the boat DC( metal in the water) ground.
for the AC ( boatside, past an isolation transformer) what purpose does the ground serve? GFCI don't need the ground..
can someone explain this?


I can see connecting the shore ground to the boat DC ground via a galvanic isolator would be good.. if shore hot touched the boats DC ground..that current then has a path back to the shore ground via the water( not good)..this should trip a breaker..


-dkenny64

[DotDun]

Originally Posted by dkenny64

been trying to follow, learn and understand the isolation transformer part

of this thread.. I understand what they do and why..
what I don't get is why connect the secondary(output side) of the isolation transformer to any of the boat DC( metal in the water) ground.
for the AC ( boatside, past an isolation transformer) what purpose does the ground serve? GFCI don't need the ground..
can someone explain this?


I can see connecting the shore ground to the boat DC ground via a galvanic isolator would be good.. if shore hot touched the boats DC ground..that current then has a path back to the shore ground via the water( not good)..this should trip a breaker..


-dkenny64

Your question is of great debate. I’m simply reciting ABYC, but I personally believe it’s safer to let the isolation transformer secondary float.