Victron isolation transformers, ABYC compliance, surveys

[GordMay]

You need overcurrent protection, and main disconndect, and [now] an ELCI, within 10 ft. of the AC inlet, whatever the downstream AC load - even just a battery charger.


ABYC E-11.11.1 An Equipment Leakage Circuit Interrupter (ELCI) or Type A Residual Current Device (RCD) shall be installed with or in addition to the main shore power disconnect circuit breaker(s) or at the additional overcurrent protection as required by E-11.10.2.8.3 whichever is closer to the shore power connection.

11.10.2.8.3 Additional Overcurrent Protection - If the location of the main shore power disconnect circuit breaker is in excess of 10 feet (three meters) from the shore power inlet or the electrical attachment point of a permanently installed shore power cord, additional fuses or circuit breakers shall be provided within 10 feet (three meters) of the inlet or attachment point to the electrical system of the boat. Measurement is made along the conductors.

[Ahmet Erkan]

Originally Posted by Jammer

Actually, Ahmet is correct that the measured AC voltage (using a modern, high-impedance DMM or an old-time VTVM) will, in the absence of faults, be about half the phase-to-neutral voltage, or in practice, around 60 volts.


But safety wise that isn't a very interesting question. In reality, any large metallic insulated object will develop measurable voltage to ground for a wide variety of reasons even if there are no electrical connections to it. The safety-related question is the amount of current that you can get to flow.

Thank you Jammer, but I also recommended the short-circuit current to be measured (see below in bold) This current is driven by the isolation transformer capacitance and passes through the diver under the boat in fresh water. The data could be useful in court when the dead diver's wife brings a lawsuit upon the misinformed boat owner who decided to connect the shore power ground to a shield that goes nowhere on his boat.


"My guess is about half the voltage measured between hot and neutral in the yard will be measured at the prop. The short circuit current should also be measured and recorded as a reference before jumpering the boat ground to yard ground."

[Ahmet Erkan]

Originally Posted by Statistical

The first thing you said that is somewhat correct. Required is incorrect as no standard requires it. It is a good idea. Alternatively one could use GFCI outlets & breakers but personally yeah I would have an ELCI on the output of the IT for "whole boat" protection.



And back to being wrong again. The ELCI woudl provide fault protection for everything between the ELCI and the IT. It would be better to add a second one (or other shock hazard protection) after the isolation transformer but it doesn't "completely eliminate" the protection.

Note if the isolation transformer is within 10 feet of the shorepower inlet ABYC standards don't require an ELCI on the input side of the IT. Ideally the pedestal has an ELCI as it can protect against shock hazards between the pedestal and the ELCI on the boat such as a worn shore power cable whose insulation has been chafed near the plug. An ELCI on the boat (with or without an isolation transformer) can't detect or prevent current leakage there.

Mr. Statistical.

If you read everything I wrote carefully, and digest it, then discuss the theory with other EE's that you know, you will eventually understand the physics behind things that I say and become a believer of pure science. Try it.
Here is an example :
The ELCI in ABYC E11 Diagram #6 does not protect the occupants of the boat.
(Because the occupants use the "hotel power" distributed in the boat from the secondary side of the isolation transformer which you agreed is not protected by the ELCI. (By the way, Hotel Power is ABS terminology, ABS American Bureau of Shipping is probably about 10,000 times more important than ABYC and I designed many products for the USN in compliance to ABS standards)
So now you can agree with two of the things that I said not just one.
Keep going you have a long road to travel to catch up with me :-)
Actually I hate bragging. It is also against all the principles in the culture I was brought up. Then again, I lived in Texas for a decade where everybody bragged and I just had the glass of red wine, prescribed by my cardiologist. Plus an extra one to make sure the medicinal benefits are gained.
Cheers my friend.

Ahmet

[s/v Jedi]

Originally Posted by ranger58sb

I've always been a bit confused by this. Our 50A/250V shorepower cable has two positive wires and a ground wire, no neutral.

I'd have thought that means an isolation transformer eliminates neutral as a return path.

??

-Chris

Most docks in the US have 120/240V 50A service which includes a neutral wire but the setup that you have is possible too. You get L1 and L2 plus a ground.

L1 and L2 are of the same phase but a transformer (like the ones hanging up in power poles) provide these with a 180 degree shift of the wave form. That transformer has a center tap that is the neutral which can be left out for 240V only service.

But at that transformer, this center tap is grounded with a rod driven deep into the ground. This means that L1 and L2 are not galvanically isolated from ground.

When you put this in an onboard isolation transformer, L1 and L2 are used to power the primary windings. You normally have two primary windings that are 120V each and connect those in series for connection to L1 and L2. The shore ground conductor protects the cabling all the wy into the isolation transformer. You must make sure there is no jumper in the transformer connecting shore ground to the transformer output ground. A Victron is delivered with such a jumper which is required by code for when the boat is hauled out and connected to shore power while on the hard. Test with a multimeter that no connection between shore ground and boat ground exists.

About return path: from L1 or L2 there are multiple return paths: besides the other L you have ground and any neutral conductors being a return path. After the isolation transformer, none of them are a return path because the transformer does galvanic isolation from every shire power conductor.

Originally Posted by K_V_B

What about setting up your boat so that you do not use shore AC directly at all.

So shore power is only connected to a battery charger. AC sources on board are fed from an inverter. With the right battery charger you also do not have to worry about what the voltage and frequency of the shore supply is.

Would that be sufficient, or do you still need something on the AC side to make this safe?

What I actually meant is no shore power at all, completely removing it. For a setup as you propose, you need to make sure that the charger is completely isolated from the boat. This means the shore ground connects to the charger but no boat ground or bonding wires connect to the charger. Also, you must make sure that the DC output terminals are galvanically isolated from shore power conductors. While I would measure everything, I would be suspicious about the DC negative being connected to shore ground. I highly distrust this and thus recommend against the setup.

My reference diagram for a simple setup with 3.6kW isolation transformer simply is the gold standard and you can simply replace the inverter/charger with a charger-only if one wishes but for other reasons it don’t recommend that either. This reference diagram is really well thought out from every possible aspect and is therefore reflected in example diagrams from every manufacturer.

Let me end this post with a little something about posts containing misinformation. There was a time I stood up against this but I was stopped by the moderators because this forum explicitly allows this because the stated goal is entertainment for an audience as large as possible. So now I mostly ignore it. In this case, these posts are highly disruptive so I did a little test by asking for qualifications as well as the intention of the poster. There was no answer which is telling.

When someone clouds their qualifications it means they don’t have them. This is a problem. I spent 6 years of full time education for my engineering degree (I finished electric as well as micro electronics and abandoned information technology when they came up with punch cards that belonged in a museum) and the amount of knowledge is shear impossible to attain without formal education. You can easily reach levels of being a very good installer but engineering means you can design the components as well as the complete system and this requires keeping a complete overview of all aspects and every bit of that vast amount of knowledge they pump into you.

I simply recommend to ignore posts on system design from unqualified people. Not only because of misinformation but also discussion is impossible when not on the required knowledge level. You get no clear answers when they lack the knowledge and instead of an answer, they jump to another subject, diagram etc. It’s simply not productive.

This is why engineers recognize other engineers with ease even when they don’t agree on something at all, which is common, but in that case each is expected to be able to defend their position on details supported with factual data from science. Being able to do that is what makes someone an engineer.

I often criticize ABYC but I do recognize that their documents are all written by engineers and of a professional level. My criticism is mostly based on those documents being outdated, not wrong. All the diagrams in E11 are correct even though I don’t recommend any of them. I believe future revisions will echo something close to my reference diagrams.

The ABYC diagrams are for professional system installers. They should follow them by the letter and have their ABYC qualification too. DIY boat owners can do this too, like Mads from Sail Life recently did.
This is the goal of ABYC: provide guidance towards safe installations.

I can easily see why people would prefer to follow an ABYC diagram rather than mine, even when the manufacturer of the equipment echoes my diagram (or I echo theirs as I studied them all of course). Also note that all my diagrams are biased towards self reliant long distance cruising and long term living aboard. This means they normally go well beyond ABYC more basic diagrams.

[Ahmet Erkan]

Blah, blah, blah.
I read all of it but I am not entertained at all.
"Chill Out" my friend. Don't get so emotional about power supplies or science.
The forum knows this, and the reason they don't throw me out is because I am polite and friendly towards even the most "unusual" people on board.
Every person is valuable, they know at least one thing much better than most people, or they are more right than most people about at least one thing.
Guess what, about all of the technical stuff you talked about above sounds correct. I have to read it several times to be able to tell myself, "yes this dude is absolutely correct" but I don't do it. The reason I don't do it is because you are too serious and not so friendly. Yes the forum gods are right, I am the customer and I want to be entertained a little.
Why can't we critique ABYC? What makes ABYC so great that the standards are not for everybody and they are only for their robots that they train only to do what is written in ABYC standards. I think even the name is a little arrogant. ABYC the last letter is "Council" a group of people who decide what is right and what is wrong and the 10 million sailors and electrical engineers in the world cannot disagree with them, not even one (ie: Diagram #6) of their recommendations? See even the most stubborn Mr. Statistical agrees that the ELCI in E11 Diagram #6 of ABYC does not protect a person inside the living quarters of a boat if he accidentally comes in contact with 120Vac or 230Vac. You don't agree, you cry and go to your room and say something like you understand why people should follow everything in ABYC instead of you recommended diagram. Show me your recommended diagram and if I see a problem, I will discuss it with you or I will become your supporter. The key words are friendliness, good intentions and honesty to achieve a win-win situation.
End of sermon and entertainment for today.
Ahmet

[Johan Leopard51]

And then my pet hate : shore power that has such bad earth to be none at all. We bleed metal because we are a lower path of resistance for probably half the boats and houses near where we moor.

My primary reason for wanting max solar on our cat is to not connect to shore power at all where she is moored normally. If the cat is free-standing electrically, am I correct that it would, in case of TERRIBLE shore power earthing, result in our not being the path of least resistance and therefore less bleeding metal to the marina?

[s/v Jedi]

Originally Posted by Johan Leopard51

And then my pet hate : shore power that has such bad earth to be none at all. We bleed metal because we are a lower path of resistance for probably half the boats and houses near where we moor.

My primary reason for wanting max solar on our cat is to not connect to shore power at all where she is moored normally. If the cat is free-standing electrically, am I correct that it would, in case of TERRIBLE shore power earthing, result in our not being the path of least resistance and therefore less bleeding metal to the marina?

As soon as you disconnect shore power by pulling the plug (not just flip a breaker), you are safe.

That said, a correct installation of an isolation transformer also 100% protects against this. A galvanic isolator does not.

If you want solid data about your protection you need a good multimeter and a silver chloride reference cell. The cell comes with a manual on how to mdo measurements DIY and you can buy it here: https://boatzincs.com/categories/too...electrode.html

[s/v Jedi]

Originally Posted by Ahmet Erkan

Blah, blah, blah.
Ahmet

Your posts seem to be too flawed to be from a bot but we had nonsense brabbel way worse than this from bots before so I am not sure.

I think you are a person using some inferior text generator enjoying it when you cause mayhem while disregarding the potential trouble it can cause for actual people on boats that would believe any of it.

One thing is sure: you have no qualifications to challenge even outdated ABYC documents other than your idea of being entertaining and thus on a serious level your post should be ignored like I do for reasons explained before so don’t bother to try to start again. All you get from me is repeat warnings for other readers.

It is correct that you are not throwing insults, which is why I didn’t block you yet, but you did falsely accuse me of attacking you. It is another warning flag when people mistake disagreement with their posts for personal attacks

[Johan Leopard51]

Originally Posted by s/v Jedi

As soon as you disconnect shore power by pulling the plug (not just flip a breaker), you are safe.

That said, a correct installation of an isolation transformer also 100% protects against this. A galvanic isolator does not.

If you want solid data about your protection you need a good multimeter and a silver chloride reference cell. The cell comes with a manual on how to mdo measurements DIY and you can buy it here: https://boatzincs.com/categories/too...electrode.html

Jedi, thanks for responding, can I clarify please?

I am battling to get the marina to even test the earth at our nearest LVac distribution point for shore power, but I suspect their earthing is atrocious.

If we have enough solar and energy storage on the Leopard 51, and assume properly installed Victron kit, then generally as a statement : by not connecting to shore power at all, we should be safer from being the sacrificial metal lamb (largest vessel in that area of marina and likely the lowest resistance of not only vessels but also the apartments and villas around us). I have heard that if your yacht is moored near another very badly wired small vessel, you can still bleed on their behalf.

I get one third of electrics (volts and amps and Ah and solar I am OK), but battle with galvanic side

[Statistical]

Originally Posted by Johan Leopard51

Jedi, thanks for responding, can I clarify please?

I am battling to get the marina to even test the earth at our nearest LVac distribution point for shore power, but I suspect their earthing is atrocious.

If we have enough solar and energy storage on the Leopard 51, and assume properly installed Victron kit, then generally as a statement : by not connecting to shore power at all, we should be safer from being the sacrificial metal lamb (largest vessel in that area of marina and likely the lowest resistance of not only vessels but also the apartments and villas around us). I have heard that if your yacht is moored near another very badly wired small vessel, you can still bleed on their behalf.

I get one third of electrics (volts and amps and Ah and solar I am OK), but battle with galvanic side

The size of the vessel has nothing to do with nothing. However IF the source of the stray current is from other vessels then yes disconnecting from shorepower completely (not just turning it off but literally no shorepower cable connected) means you can't be a ground return source for stray current and as such not affected by other veseels.

I would point out that many a boat owner absolutely positively convinced that stray current corrosion is the fault of other boats has found out later they were the source of their own problems. In that case disconnecting from AC will not help you. You will need to find and fix the source of the leakage on your boat.

No idea what you think apartments and villas have to do with it. Pretty sure they don't have DC systems leaking stray (DC) current into the water.

[Johan Leopard51]

Thanks Statistical,

Like said : galvanics is greek to me. I understood stray current of anybody on the same AC network (all the houses, apartments boats that are below same 11kV transformer) would ordinarily (if transformer has a proper earth) flow to that proper earth. If our shoreside transformer has bad earth, then stray current of all users would follow path to lowest resistance.

On recent outhaul there was current from our cat to yard when yard power connected to the cat, but with our systems live and no yard cable connected, there was no current from cat to yard. Yard manager said they have earth problem.

[ranger58sb]

Originally Posted by s/v Jedi

Most docks in the US have 120/240V 50A service which includes a neutral wire but the setup that you have is possible too. You get L1 and L2 plus a ground.

In our case, with isolation transformer on board, that's accomplished by simply using a shorepower cord (Cablemaster cord) that has no neutral wire.

So the pedestals still have all 4 conductors, but the boat only sees 3.

-Chris

[s/v Jedi]

Originally Posted by ranger58sb

In our case, with isolation transformer on board, that's accomplished by simply using a shorepower cord (Cablemaster cord) that has no neutral wire.

So the pedestals still have all 4 conductors, but the boat only sees 3.

-Chris

Exactly, that’s what I do. I could also change my Northern Lights genset to 240V so I got 240V inverter/chargers and only get 120V after an autotransformer that takes the 240V and creates the familiar 120-0-120 feed like the standard US feed.

[rslifkin]

Originally Posted by s/v Jedi

Exactly, that’s what I do. I could also change my Northern Lights genset to 240V so I got 240V inverter/chargers and only get 120V after an autotransformer that takes the 240V and creates the familiar 120-0-120 feed like the standard US feed.

The only issue with doing that is that if you have lots of big 120V loads you'll need space for either a very large autotransformer or multiple in parallel to support enough imbalance between the 120V legs. And if you need to be able to use a single leg of 120V / 30A shore power you also need another transformer to step that up to 240V. Space for all of that equipment is the biggest thing stopping me from following your lead there.

[ranger58sb]

Originally Posted by s/v Jedi

Exactly, that’s what I do. I could also change my Northern Lights genset to 240V so I got 240V inverter/chargers and only get 120V after an autotransformer that takes the 240V and creates the familiar 120-0-120 feed like the standard US feed.

Originally Posted by rslifkin

The only issue with doing that is that if you have lots of big 120V loads you'll need space for either a very large autotransformer or multiple in parallel to support enough imbalance between the 120V legs. And if you need to be able to use a single leg of 120V / 30A shore power you also need another transformer to step that up to 240V. Space for all of that equipment is the biggest thing stopping me from following your lead there.

We have some kind of transformers that create 120VAC from the main 240VAC feed. Still fixing other stuff on the boat, so understanding those hasn't bubbled up to the top of my To-Do list yet...

Four of our 120VAC loads are just low-voltage interior area lighting; haven't figured out why somebody thought low-voltage 24VAC lighting might be useful.

-Chris