Where to locate Galvanic Isolator

[Emmalina]

Made a galvanic isolator out of 4 big silicon diodes Stuck it in epoxy and forgot about it. Not in mariners often but the 1-2 volts it eliminates ain't going to make it very hot..

[Pelagic]

Originally Posted by Ahmet Erkan

....My first safety recommendation for onboard isolation transformers is to insulate the transformer case from the boat and connect the shore power grounding (green) conductor directly to the transformer case/core.

Hi Ahmet, to help clarify take a look at the grounding diagram of the Victron Isolation transformer in this Data sheet download
https://www.victronenergy.com/isolat...-3600va-7000va

My understanding is that the shore side cables including ground is connected inside the transformers core which is completely insulated from the case and mounting bracket.

Inside it breaks continuity and connects to Ship Side via magnetic (induction?)

I actually took mine apart when first purchased to see how it works and can confirm that the core is insulated from the case.

From Data Sheet
The best solution to avoid galvanic corrosion and at the same time prevent any unsafe situation is to install an Isolation Transformer to connect to the shore-side supply. The Isolation Transformer eliminates any electrical continuity between shore power and the boat. The shore power is fed to the primary side of the transformer and the ship is connected to the secondary.

The Isolation Transformer completely isolates the boat from the shore ground. By connecting all metal parts to the neutral output on the secondary side of the transformer, a GFCI will trip or a fuse will blow in case of a short circuit. Soft start is a standard feature of a Victron Energy isolation transformer. It will prevent the shore power fuse from blowing due to the inrush current of the transformer, which would otherwise occur. It is also recommended, for optimal safety, to connect the secondary neutral of the transformer to ground when the boat is out of the water.

[Sailorlou]

Originally Posted by Ahmet Erkan

Mr. Sailorlou and supporters of Mr. Sailorlou,
This discussion is not about you or I. Electrons couldn't care less about credentials, titles or experience, electrons care only about the laws of physics. Therefore I am going to pretend I did not hear any of your arrogant chest beatings and personal attacks and focus on the technical comments and recommendations that you have made to the fellow sailors who are looking for expert advice. First of all, I am going to explain that the most unsafe action you have recommended is connecting the case (the core and metal enclosure) of the isolation transformer to the underwater metals and the bonding system of the vessel. The ungrounded conductor/s of the shore power cable have to penetrate the case of the transformer thus have an opportunity to short to the case. Since you have also recommended that the shore power grounding conductor should not be connected to the underwater metals of the vessel, a short from the ungrounded power conductor/s to the transformer case is going to energize the underwater metals and create a high voltage gradient which is going to be fatal to swimmers, divers and all living creatures around the boat, and especially so in a fresh water environment. Electronic sensors and only if they are installed and happen to be operational may prevent a fatality. Metal (steel) vessels will have a lot more opportunities to short to the ungrounded conductors of the shore power cable.

OK Mr. proud EE medical grade transformer designer, explain away the safety hazard described above and then we will continue to the next hazard.

My first safety recommendation for onboard isolation transformers is to insulate the transformer case from the boat and connect the shore power grounding (green) conductor directly to the transformer case/core.

Ahmet,

You seem to be trying to turn this into a pissing match not a discussion. That's why I usually don't respond to these forums. If you took offence to my original wording, that's your problem.

You miss quoted me in my original statement, I did not say you connected the case of the transformer to the shore ground, I said you connect shore ground to the shield (also known as the drain) which is internal to the core and isolates shore ground from the boat. The shield is not connected to the case.

I thought about writing a tutorial on the construction and operation of Power Isolation Transformers after your statements, but have decided to only correct you on your miss-quote.

I do not want to get into a pissing match, it's a waste of my time.

I designed isolation transformers before I retired and went sailing, I understand the technology very well.

Palagic has purchased, in my opinion one of the best toroid isolation transformers on the market. The wiring supplied by Victron is correct.

I'll leave it to your imagination as to which toroid isolation transformer currently on the market is my design.

[HankOnthewater]

Originally Posted by Emmalina

Made a galvanic isolator out of 4 big silicon diodes Stuck it in epoxy and forgot about it. Not in mariners often but the 1-2 volts it eliminates ain't going to make it very hot..

This is what I did on my previous boat, cheap and effective. Diodes need to be rated at least 60 to 100 amps to allow a fault condition to trip the RCD, that may take up to 30 milli seconds.

Regarding isolators getting hot..... if they are hot than you have a problem!

Regarding the previous comments about testing...... yes, one can check the (diodes in a) home built galvanic isolator by using a simple multimeter set to 'diodes', as in self-built units you may be able to access all connections of all 4 diodes. In an off-the-shelf unit there are only 2 connections, one connect them either way, but testing ... never done it myself, but I guess with a small 9 Volt battery and a resistor (ie 10 Ohm) to limit the current (to ie 1 Amp) and then measure the current either way: should be more or less equal and a bit less than the 1 amp short circuit amp. Can anyone confirm this is a valid way of testing? If it is, then maybe such testing is a chore that can be added to the boat maintenance program ie yearly.

Or there may be very clever people on CF that can design and build a tester where one pushes a button and a red or green LED lights up, green for "OK" and red for "buy new one".

I have added an image from the net.
Shows where to connect it, and also a diode diagram.

[Sailorlou]

Originally Posted by Sailorlou

Ahmet,

You seem to be trying to turn this into a pissing match not a discussion. That's why I usually don't respond to these forums. If you took offence to my original wording, that's your problem.

You miss quoted me in my original statement, I did not say you connected the case of the transformer to the shore ground, I said you connect shore ground to the shield (also known as the drain) which is internal to the core and isolates shore ground from the boat. The shield is not connected to the case.

I thought about writing a tutorial on the construction and operation of Power Isolation Transformers after your statements, but have decided to only correct you on your miss-quote.

I do not want to get into a pissing match, it's a waste of my time.

I designed isolation transformers before I retired and went sailing, I understand the technology very well.

Palagic has purchased, in my opinion one of the best toroid isolation transformers on the market. The wiring supplied by Victron is correct.

I'll leave it to your imagination as to which toroid isolation transformer currently on the market is my design.

Ahmet,

One more thing I would like to add.
Before you build and wire your dream 65 foot metal boat, I would like you to contact Kevin Ritz (there are a couple of links below about Kevin). Please bounce your wiring concepts off him and take to heart what he has to say.
Kevin previously was an ABYC instructor and ABYC’s Pacific Regional Representative. He later became ABYC's Lead Instructor and Chapter Development Manager. Kevin also founded the "Electric Shock Drowning Prevention Association (ESDPA)". He is an expert in boat and dockside electrical systems. The reason Kevin began working for ABYC was because his 8 year old son died from stray current from a faulty electrical system on a boat.
I have had the pleasure of meeting Kevin and discussing the proper construction, wiring and application of Isolation Transformers on two occasions.
Isolation Transformers are the only way to completely isolate your boat from the shore side power. As well as preventing a shock hazard on your boat transformers block any development of both DC and AC stray current associated with a dockside power source. The most important characteristic of an isolation transformer is the physical disconnect of the shore power source including the ground from your boat. A galvanic isolator does not actually isolate your boat from anything. The name is misleading, the only purpose of a Galvanic Isolator is to block DC stray current. It does not block AC stray current and does not isolate your boat from shore ground and does not prevent electrical shock hazard. If you have an isolation transformer on your boat, you have no need for a galvanic isolator.
Here are two links you should check out. You can get Kevin's phone number from the fist link in the contacts section. Please call him for your own safety and edification.

Electric Shock Drowning Prevention Association - Home

What every boater needs to know about Electric Shock Drowning. - Great Lakes Scuttlebutt

[Oceansailor]

Hi Sailorlou, Do you have an opinion about the Mastervolt Isolation transformer that is doing the job electronically. https://www.mastervolt.com/products/...a-lightweight/

[Pelagic]

Originally Posted by Sailorlou

You have made the best choice. Isolation Transformers actually isolate you from shore ground by breaking the physical connection and transferring power through a magnetic field. Isolation Transformers "Isolate" you from AC & DC stray currents and help prevent electrical shock hazards.

Hi Sailorlou
Thanks greatly for clarifying.

Is there a proper name for that
" Magnetic Field" that energises the secondary block to ship.
I called it an Induction connection, but I know that is probably wrong?
Sorry...unknowns like this bug me![emoji49]

[Sailorlou]

Originally Posted by Oceansailor

Hi Sailorlou, Do you have an opinion about the Mastervolt Isolation transformer that is doing the job electronically. https://www.mastervolt.com/products/...a-lightweight/

I am familiar with the Mastervolt isolation transformer.
Mastervolt manufactures some very high quality marine electrical devices and their Mass GI 3.5 and Mass GI 7.0 toroid core transformers are no exception.
Mastervolt is able to keep the size and weight to a minimum by transforming the power at a much higher frequency then a standard toroid power core.
However this approach does make the transformer much more complex and more expensive to purchase.

[Sailorlou]

Originally Posted by Pelagic

Hi Sailorlou
Thanks greatly for clarifying.

Is there a proper name for that
" Magnetic Field" that energises the secondary block to ship.
I called it an Induction connection, but I know that is probably wrong?
Sorry...unknowns like this bug me![emoji49]

You are probably referring to Magnetic Flux Induction or Induced EMF (Electromotive Force). They are basically the same thing.
Faraday’s law of induction states that an electromotive force is induced by a change in the magnetic flux.
For the layman EMF is voltage.

[Ahmet Erkan]

Pelagic and other reasonable folks,
Here are a few recommendations when bringing in AC power to your boat.
1. Connect the shore power grounding (green) conductor to your hull ground (aka underwater metals bonding bus which is connected to the negative terminal of your DC system, and the engine block) This connection MUST exist to insure your boat is safe.
2. Install a galvanic isolator in series with the shore power grounding (green) conductor. This is HIGHLY RECOMMENDED to prevent other boats in the vicinity to have an adverse effect on your bonding and cathodic protection systems that protect your underwater metals.
Use a galvanic isolator monitoring system to test the galvanic isolator periodically and automatically to verify it is operational.
3. Install an isolation transformer and surge protection device to protect your sensitive electronics from lightning and power line transients at the marina. Insulate the core/case of the isolation transformer and connect the shore power grounding (green) conductor to the core/case of the isolation transformer. You MUST connect the secondary winding neutral conductor to the hull ground to implement ground fault protection in compliance with the NEC national electrical code in USA. Secondary neutral may be left unconnected if a military power system controller is installed that monitors the leakage currents and has the capability to ride through ground faults safely.
4. When "experts" state their credentials and tell you to do things that are contrary to what is listed above, ask them what happens to a diver near your vessel if an ungrounded shore power conductor shorts to your hull ground. (ie: this could happen with a high probability through the case of your miswired isolation transformer due to misguided installation instructions or if your shore power cable gets crushed between the dock and your metal hull or by some other unforeseen insulation failure mode)

NOTE : If the "experts" start talking fast about magical shields and providing safety through the transformer with induced EMF or any other nebulous phenomenon just say, thank you for the very valuable advice and walk away. If the expert says go ahead and short the shore power hot conductor to your engine block and if the CB at the shore power pedestal does not trip I will dive under your boat. If this happens you will either never see that guy again or he may really know something that nobody else knows.
All the best.
Ahmet

[rgleason]

This video seems pretty clear to me, a galvanic isolator protects your boat and swimmers from stray currents in the grounding system, and the galvanic transformer cleans up the power signal coming into the boat. As I understand it, I believe we are comparing two entirely different functions and devices that are used for very different purposes. You may need both devices.

https://www.youtube.com/watch?v=zGB2ch7hkx4

PS:
In further reading it appears that good galvanic transormers take care of both problems. Sorry. I was wrong.

[Sailorlou]

Originally Posted by Ahmet Erkan

Pelagic and other reasonable folks,
Here are a few recommendations when bringing in AC power to your boat.
1. Connect the shore power grounding (green) conductor to your hull ground (aka underwater metals bonding bus which is connected to the negative terminal of your DC system, and the engine block) This connection MUST exist to insure your boat is safe.
2. Install a galvanic isolator in series with the shore power grounding (green) conductor. This is HIGHLY RECOMMENDED to prevent other boats in the vicinity to have an adverse effect on your bonding and cathodic protection systems that protect your underwater metals.
Use a galvanic isolator monitoring system to test the galvanic isolator periodically and automatically to verify it is operational.
3. Install an isolation transformer and surge protection device to protect your sensitive electronics from lightning and power line transients at the marina. Insulate the core/case of the isolation transformer and connect the shore power grounding (green) conductor to the core/case of the isolation transformer. You MUST connect the secondary winding neutral conductor to the hull ground to implement ground fault protection in compliance with the NEC national electrical code in USA. Secondary neutral may be left unconnected if a military power system controller is installed that monitors the leakage currents and has the capability to ride through ground faults safely.
4. When "experts" state their credentials and tell you to do things that are contrary to what is listed above, ask them what happens to a diver near your vessel if an ungrounded shore power conductor shorts to your hull ground. (ie: this could happen with a high probability through the case of your miswired isolation transformer due to misguided installation instructions or if your shore power cable gets crushed between the dock and your metal hull or by some other unforeseen insulation failure mode)

NOTE : If the "experts" start talking fast about magical shields and providing safety through the transformer with induced EMF or any other nebulous phenomenon just say, thank you for the very valuable advice and walk away. If the expert says go ahead and short the shore power hot conductor to your engine block and if the CB at the shore power pedestal does not trip I will dive under your boat. If this happens you will either never see that guy again or he may really know something that nobody else knows.
All the best.
Ahmet

OK, here is my last input on this subject. Don't believe me, don't follow any advice I may have put forth. Don't follow anyones advice, at this point I couldn't care less.

Just follow your isolation manufactures' recommendations on installing an isolation transformer. Below is a link the the user manual for the Mastervolt Isolation transformer. within its pages a is a clear diagram showing the proper wiring.

Nuff said.

https://images.mastervolt.nl/files/M...2135_04_EN.pdf

[rgleason]

Here is the article that I read, which clarified that a galvanic transformer takes care of both problems. Isolation Transformers - Seaworthy Magazine - BoatUS
small

It looks like it there is quite literally no location for this on my boat small although it would be a good safety device!
Thanks Sailorlou for the link to mastervolt. I'm trying to understand what is needed for a very simple 2 receptacle 120vac 30amp shorepower to meet reasonable modern requirements.

[Pelagic]

Originally Posted by Sailorlou

Just follow your isolation manufactures' recommendations on installing an isolation transformer. Below is a link the the user manual for the Mastervolt Isolation transformer. within its pages a is a clear diagram showing the proper wiring.

Nuff said.

https://images.mastervolt.nl/files/M...2135_04_EN.pdf

Comparing my specifications I found the Mass Isolation Transformer GI 7 to be quite a bit more sophisticated than my Victron 7000w unit.


But the shore power connection is the same as you explained in my manual


I am happy with my unit and don't see any problem with shore power demands in Asia.
I think the reality for cruising boats is becoming more Solar, less need for Shore Power unless you are a dockside palace.

Ironically, the marina came to tell me today that they needed to cut shore power to pull cable.

You can see where the rats have got to the Cable and I can only imagine how hot the shore power cable was getting at high tide.[emoji4]



As I was already on Invertor running 2 fridges and one small air con, my net loss @ 24v was about -4amps. My 4 Sunpower panels are giving me about 38 amps

[Ahmet Erkan]

Originally Posted by Sailorlou

OK, here is my last input on this subject. Don't believe me, don't follow any advice I may have put forth. Don't follow anyones advice, at this point I couldn't care less.

Just follow your isolation manufactures' recommendations on installing an isolation transformer. Below is a link the the user manual for the Mastervolt Isolation transformer. within its pages a is a clear diagram showing the proper wiring.

Nuff said.

https://images.mastervolt.nl/files/M...2135_04_EN.pdf

Dear Sailorlou,
In our community, sailors need to consult with the electrical experts like yourself and get their advice on electrical matters.
Please care more, and explain the product you are evidently recommending for our boats.
I was unable to find a "clear diagram" in the manual. Elaborate instructions and warnings say do not connect the "earth ground" to the "protective earth ground"
Is there a galvanic isolator (ie: inverse parallel diodes) inside the transformer case? Is the "earth ground" or the "protective earth ground connected to the chassis of the enclosed transformer? No instructions state where the "protective earth ground" should be connected.
Could you please explain why we should trust this manufacturer with our lives and feel safe by connecting wires into six terminals inside their magic box that the manual does not say where the wires go and not know where to connect the "protective earth ground" external to the transformer?
I apologize if I came across as pontificating, but if possible lets leave that behind us and try to give the best and most accurate advice to our fellow sailors.
Thank you.
Ahmet