Over the years I have bought three boats fitted with a shore power system and all of them were primed to kill, including our new-to-us J/109.
Sorry, I know that's a dramatic first sentence but, seriously, this is scary stuff.
In the first two cases the problems were sins of commission where the AC system was wired incorrectly, but with our latest boat the problem is sins of omission, in that, although Tillotson Pearson wired the boat to ABYC recommendations properly when they built her 17 years ago, stuff has failed since then and not been fixed, leaving a situation that is, in many ways, the most dangerous of the three boats.
The point being that even if the new-to-us boat (or even brand-new boat) we buy was originally wired correctly, there are some things to check before we plug the boat into shore power.
So let's dig into what those checks are, take a look at the truly scary shit I found, and then the fixes:
I can understand the frustration about poor workmaship. Being a hardware store manager, I have observed the almost complete lack of ownership mindset that most people have. We live in rural America and customers are shocked when I tell them they are their own water utility company when it comes to water problems. They are frustrated at the inconvenience breakages give and at the same time unwilling to own their “crap.” Once you decide to truly own your stuff and get past that “someone else is at fault” loop, taking steps to minimize future frustrations look possible. It’s actually empowering once you swallow that big pill.
Not a boat owner, but those wires above the breaker look like they are touching the bolt above. Serious lack of wiring protection in that area, period. Cheers, Marc
Good point about how freeing it is when we finally decide to just get a grip and take ownership. I just went through exactly that with a plumbing problem that the plumbers just could not fix. A couple of hours Google research and I had it solved even though I know nothing about house plumbing.
And yes, you are right about the wires, but they are all low voltage, so while a poor set up are not what I’m referring to. That said I will clean it up.
Regarding your assumption:
”Think of an ELCI as a Ground Fault Interrupter (GFI) for the whole boat that will, I’m near certain² (assuming that the boat’s AC ground is fully bonded to her underwater metals), trip if the live wire shorts to the case of any equipment, even if the shore power ground wire is disconnected.”
You are correct, that is exactly what would happen – it would even happen if the neutral wire would short.
The reason is that an ELCI is actually a device that measures the current differential between the live wire and the neutral wire. When the difference is zero (meaning that all current flowing in the live wire goes back via the neutral wire), the ELCI does nothing, and current flows in a complete circuit as it should.
If the differential is above a threshold set by the manufacturer (30 milliamps in Europe with 230V systems), the ELCI trips, since current is flowing (leaking) outside the circuit, i.e. it is shorted.
In a fully bonded boat, any metal part should be a path to ground (well, water, in case the ground wire is disconnected, but anyways). If either the live or the neutral leaks to anything metallic that is bonded to ground, ELCI will see a differential and trip.
This obviously assumes that the ELCI is THE VERY FIRST device in the circuit after the shore power receptable!!!
A tricky situation might occur in a non-bonded boat such as mine:
a non-grounded metal object might become energised if a live wire touches it, but the ELCI will not detect that until a person touches it and something that is grounded, and completes the circuit. Think of a stanchion and a wet wharf. Even in this scenario the ELCI will very, very likely save your life, since the current that it allows before tripping is so low that it should not kill you.
We did try this in a lab with our electricity professor, and it worked fine (no, we did not touch the wires).
ELCIs have fortunately been mandatory on new installs on all shore power systems (and all wall outlets in kitchens, bathrooms and anywhere outdoors) for quite some time at least in Finland, and I hope that applies EU wide. They work very well in protecting you around water.
Actually, when we tested our boats ELCI with an electrical engineer friend of mine, we could not get a reading for the current needed to trip it, since the marina’s ELCI that was upstream was just that much more sensitive that it always tripped first 🙂
An ELCI costs very little money, and I think everyone with any AC on their boats should get one tomorrow.
Great to have that independent verification. My reasoning was exactly the same as yours, but given the seriousness of the subject I wanted independent verification and that you have actually tested this is a huge bonus. Thanks so much.
As you say, the with a non-bonded boat the situation is not quite as clean, but still, I agree, given the trip threshold there’s a very good chance that it would still save a life.
Yep. The ELCI is a very clever little device. You just run both the AC Hot and AC Neutral wires through the hole in the middle of a small transformer core. As long as all current going out the Hot comes back through the Neutral, the total flux induced in the core is zero.
If there’s a current imbalance, i.e. if current going out the Hot comes back through any path other than the Neutral, the flux induced in the core will be non-zero. There’s a little electromagnet driven by the secondary side of the transformer core that pops the breaker open if the current imbalance exceeds the threshold.
Simple, very reliable, and a big boon to safety. Just make sure you get one that acts on both poles (as I think all marine-legal ones do); interrupting the Hot side only won’t save you if the dock is wired backwards.
(I might add that ELCI, RCD, GFCI, ALCI, LCDI are all just different names for the same mechanism, which can be integrated in a number of different ways, eg. as part of a main breaker, or in a receptacle, or as a standalone whole-boat device, or to protect just one circuit…..)
Hi Vesa and Matt,
I have removed the qualification from the post, thanks
Should the ELCI be installed on the boat; down stream of the dock cord, beyond the boat plug and boat cord socket, and downstream of maybe 10 feet of the boat interior wiring? Should it not be at the pedestal end of the dock cord? There, as a part of the dock cord, no on boat modifications would be required, it would be easier to implement, and it would provide protection not provided by an ELCI installed aboard. Of course, all marinas should provide an ELCI as a part of the dock pedestal, but until then, why not provide your own as a part of your boat’s dock cord? To me it looks like the “good, fast, cheap” solution to providing a 30mA leak to ground protection to my boat.
Google quickly found this one and several others. https://nssltd.com/boaters/ Their
50 ft, 30A cord with an ELCI at the dock end would provide what I think is better protection to my boat than an onboard ELCI.
I wonder what ABYC thinks of this solution.
As I remember from my reading, ABYC does not mention that kind of in-cable unit. My guess would be that the reason is that said unit would be much more vulnerable to damage that a permanently mounted unit and the other drawback is if someone plugs the boat in directly without the in-cable ELCI in place a very easy mistake to make since in-cable ELCIs are rare. This is just the kind of ambiguity that regulators hate, and for good reason.
The other issue is that since it’s a pig tail cable adding it also adds two more connection points, which is a poor idea since this kind of plug is very vulnerable to poor connections and overheating.
Add it all up and I would not use one as a replacement for a permanently mounted ELCI in a sheltered location inside the boat.
Hi John and all,
It may be of interest that many RV owners will use an interface device between the “shore power” pedestal and the vehicle. The worry is clearly not ESD, but rather the issues of surge protection and warnings about low and/or high voltage, polarity, ground problems and the like. RV parks often share with marinas poorly designed and poorly maintained electrical systems that get regularly abused by their visitors.
My best, Dick Stevenson, s/v Alchemy
I hear you, but the reasons for that are different than the example William and I are discussing.
The key difference being RVs don’t operate in water so the swimmer risk that is so much of the reason for having an ELCI on a boat is not present.
That said, I did buy and use a socket tester for our recent RV trip.
That difference is exactly what I meant when I wrote, “The worry is clearly not ESD…” Perhaps I should have been clear that I was referring to electric shock drowning, ESD.
My best, Dick
Aha! That makes sense. I definitely jumped to conclusions, sorry.
I can get around the issue of a pig tail ECIL unit with its mid-cable plug and socket by buying the unit listed on the website I referred to with a 50 ft cable.
By replacing my existing (and old) 50 ft shore power cord with that cord, I’d also have little chance of having my shore power hooked up in a marina with a cord without a ECIL because I have never had a marina offer to hook up the boat with any cable other than mine
But, there is no avoiding the fact that the ELCI would be in an exposed and vulnerable location dangling in the shore power cord below the marina power pedestal.
By the way, it is very hard to imagine why anyone would spend $1600 on an isolation transformer and not spend $30 on an ELCI, since AFAIK an isolation transformer will not save you from a scenario that an ELCI will.
I am amazed that ABYC would exempt ELCI’s based on isolation transformers!
Does anyone know why on earth they do?
Where did you get a ELCI for $30? Mine costs over $300 although it does have added features, a case and the capability to expand to more breakers.
As to the ABYC exemption I can see the logic in that an ELCI in the circuit before the isolation transformer would not trip in the event of a fault after it, so, as I say in the article, the smart thing to do is move the ELCI to the boat side of the transformer, where it will still work.
on my boat I installed an ELCI device like this: https://www.amazon.com/NDB1L-32C-16-240V-Circuit-Breaker-Sensing-Leakage/dp/B00NTVBH2C
Trips on overload above 16A, and on a ground fault delta of 30mA. No need to install expensive (300+) devices as they don’t do anything else, especially if you have mounted them in an according IPx casing.
Hum, I’m just not sure I would trust a $30 unit from some no name operation procured on Amazon for this vital function. Also I wonder how an insurance company would react.
I hear you that it’s probably the same thing, but given that it’s not even called an ELCI and further given the huge liability I will stick with a company like Blue Sea that everyone knows about and that I have had good experiences with in the past. And yes, I know, they probably get their breakers from some no name company!
I got mine from wholesales, and forgot to translate Euros to Dollars. Seems that hardware stores ask more like 50-80 USD.
The thing is: you don’t have to go Bluesea on these things – just get a regular household RCD/GFI and install in a plastic casing that is at least IP54 rated.
DC panels and busbars are a different story, and with those, the most likely cheaper alternative is automotive gear which does not last around salt water – there I will happily pay for Bluesea.
Any reputable brand like ABB, Hager, Schneider or similar will do, as long as it handles the current you need (mine was 25A and is combined with a circuit breaker).
ABB calls these Residual Current Circuit Breakers
Proper casing and they do fine in a boat. Even cruise ships use them.
A GFI ’becomes’ and ELCI simply by making sure it handles all the current used downstream, and installing it right after the shore power receptacle – or the isolation transformer if you have one.
I’m sure you are right in theory, but given the liability involved I’m more comfortable using a marine device from a well recognized name like Blue Sea. Given the way that insurance companies are behaving these days I can easily see them disallowing a claim if something bad happened just because the device was not specifically classed as a marine ELCI.
Seems like Mastervolt requires not just one but two GFIs when installing their isolation transformer:
one at the input, another at the output.
John, when you mentioned the hazard of wiring the transformer incorrectly, did you mean that the connection between the output neutral & output protective earth is often skipped?
Yes that’s it, but I don’t want to get into turning this into instructions on how to wire an isolation transformer. To do that people should be able to read and fully understand the manual as well as ABYC or ISO/CE or hire someone who can.
The point being that the place that the system should be referenced to ground changes when you install an isolation transformer (also with inverters and generators) and this is one of the hardest things for a lay person to understand and getting it wrong is one of the most dangerous. This is not something I want to be advising people on, or discuss here, since most people just don’t have the basic electrical understanding to mess with ground referencing the system safely.
For example most lay people think that current returns to ground, which is, as you and I both know, fundamentally wrong and a misunderstanding that leads to all kinds of dangerous mistakes.
Worth noting: All of the insurance carriers we talked to while getting coverage set up for Maverick V advised that boats whose shorepower systems do not comply with current ABYC standards are uninsurable, period. They no longer accept “it complies with the standards that were in effect when it was built.” A transfer of ownership triggers an underwriting requirement to bring everything between the dock end of the cord and the main AC distribution panel up to current standards, including a marine-rated ELCI and main breaker with reverse polarity indicator, or else they will not extend any “afloat and navigable” coverage.
This may not be universal, but it is true of all the carriers we considered.
With that in mind, I would have no qualms about using “well, the AC system is probably uninsurable and X,Y,Z will need to be replaced either now or the day after I buy it” as a bargaining chip in just about any purchase of a boat where any of that stuff is less than perfect.
And, in any new design, I would – unless there is a very compelling reason to do otherwise – limit the AC shorepower system to just an isolated battery charger, and design all systems to run either from the DC main bus or from an inverter-powered AC bus that has no link to shorepower.
Good to hear on the insurance companies pushing for this, but clearly this is not universal since our new boat changed hands twice with two surveys (I have both) that failed to call her out for non-compliance.
As to going to a limited system, that’s certainly an idea, however this boat has a pretty good AC system with GFI sockets, a water heater etc, so I think I will probable just go through the whole thing for compliance and leave it at that.
with my refit I installed a “limited system” somehow as you described. I have two AC chargers that can be switched separately, but I needed some AC in the boat as there are outlets and a LED/AC lighting in the main cabin. This circuit is separately switchable, and the ground fault line is only connected to the bonding (steel hull) if the this circuit is enabled. This setup allows me to have the chargers running while still no AC aboard.
I assume you are referring to an inverter or generator. If so the correct switching of the ground is covered in both ABYC and CE code, but is generally as you say.
The point I’m making here, as I did in the summary, is we don’t want this thread, or my article, to be mistaken by others as “everything they need to know” about AC safety or worse still “crowd sourced AC safety”. Now there’s an oxymoron!
Yup, absolutely, see also my other post here “unless you are an expert and really know your stuff”. AC is inherently dangerous, especially on the water. No one should “assume” to know what he/she is doing, it might be one of the last assumptions.
(BTW, my surveyor recommended my solutions to Pantaenius being “state of the art or better”. Just wanted to brag a bit about it 😉 )
In Europe there is no ABYC but we have all these ISO and CE stuff. For AC, not a lot of difference except that a lot of things (ELCI for example) are required rather than recommended.
I would be the first to say that all of these things are WAY better in Europe, surveys, code, and boat yard techs, except you lot are getting way too big headed already around all the German-Tool-Fanboy stuff around here, so I won’t feed that fire.
Hi John, marine electrical installations in Australia and NZ are covered by AS/NZS 3004 part 2, 2008 & 2014.
An earth leakage breaker is obligatory both on the vessel’s connection point to shore power i.e whole boat protection and then further ELCB’s are required for outlets around the vessel, these must be downstream of any onboard power source (inverter or generator).
In NZ any boat connecting to shore power must be inspected by a licensed electrical inspector every 4 years with a certificate (called an EWOF – Electrical Warrant of Fitness) being issued. Same applies for Motorhomes and caravans connecting to the mains- they have a separate standard.
We do have some grey compliance areas for boats built pre 2008, and this requires the inspector to apply some judgement, some of whom have been a bit over the top.
Every new production boat arriving in NZ from Europe has to have its AC (and LPG) installations upgraded to comply with the local standards
That’s great to hear. We have a long way to go in North America.
Is that an RF cable running across the GI and other AC cables, will give a nice buzz on your VHF?
My set up is a 120 V boat in a 240 V world; fortunately the isolation transformer acts as a stepdown transformer and I believe it still provides the required protection and dual voltage. I would do the full conversion but it would mean new inverter, new gererator, new Aircon, a whole bunch of powertools becoming paperweights, and for no real gain for what we really use onboard. If someone would just send me a 120 V nespresso machine, I’d be set!
Assuming (don’t, check) that your isolation transformer is wired right, the fact that it is in step down mode will not change anything on safety.
One other thought you are probably aware of. The transformer does not change the frequency therefore anything with a motor in it that has not been specifically designed to be frequency agile will tend to run hot on 50 Hz and could even start a fire.
I would particularly worry about the things like the air that might run for long periods.
Thanks John, yes, the aircon situation is annoying and as a result not operated very often except when I’m onboard dockside doing sweaty maintenance in the summer.
Related question; is it safe to use a portable generator through the shore power inlet to an isolation transformer? I assume only the run from the generator to the transformer is essentially unearthed, or do generators have their own earth somehow?
A generator, whether in the power plant or on board, always generates a potential difference between two conductors. In a power plant, one of these conductors is always the “real” earth/ground, whereas a generator of course has no “earth”. With a line from the power plant, you can touch “neutral” without any problems, but never the “phase” (if you are standing on the ground). With a line from a generator you may touch each conductor separately because there is no potential difference to earth – but never both at the same time. You can of course define one line of the generator as “earth” and connect it to the bonding system, but I would strongly advise against it, unless you are an expert and really know your stuff. What must not happen is that the generator gets a connection to shore power.
I think the bottom line answer her, is no, don’t do that. See my answer above as to why. Just another reason to install an isolation transformer.
That’s a very good question and I think the answer is in fact a BIG no. I had not thought of this but by plugging a generator into shore power we are ending up with a dangerous situation since no where are the neutral and ground conductors tied together and grounded to the boat’s bonding system.
With a built in generator or inverter, there is a relay that performs this step when the generator starts, but when just shore power is used said relay kicks out and breaks the contact since the neutral and ground conductors are connected together back at the marina transformer and this should never be done twice in the same system.
So, given that, the only safe way to use an external portable generator with the shore power lead plugged into it is to install an isolation transformer, since in this case the ground and neutral conductors are tied to ground on the boat side of the isolation transformer.
All of this is covered my ABYC recommendations and ISO code.
I definitely just learned something.
A portable generator must never be used as power source for an AC network (like in a house, or a boat).
[Edit – it is perfectly benign if the portable gen powers an isolation transformer only]
The reason is that a portable generator has no earth-neutral and as such no ground fault capability. In technical terms but simplified a portable gen provides an ungrounded IT network, while shore power (and a correctly installed inverter) provide a grounded TN network. If interested the different network types are discussed for example here: https://www.electrical-installation.org/enwiki/Characteristics_of_TT,_TN_and_IT_systems
Note: electricians study this topic years long for their final certificate, so no DIY should try to mess around with this, just leave it to the pros. It cannot, however, be wrong to be educated so one can distinguish between the “real” pro and the usual cable splice guy (no offense meant)
At least in Canada it’s perfectly acceptable and commonly done to power a house with a portable generator. A special change over switch is installed and this is in the code. The key, I think, is that the ground reference where the neutral and ground are tied together at the primary to secondary transformer is still in place even though the mains power is down. But that is not the case, as you point out, on a boat.
I also think you are right that going through the isolation transformer may be a safe way to do this but once again I need to think and draw before committing myself on that.
And I totally agree that the concepts around ground referencing of AC power and what is neutral are complex and should not be played around with by amateurs…or boat yard “professionals”. Hell, ground referencing makes my head hurt, and I have training, although not specifically about that subject.
Bottom line, wire your boat to ABYC or ISO/CE and don’t wing it.
Sorry, missed the isolation transformer in your comment. With that I do think it’s fairly safe. However there is one scenario that could be bad in that if the either input side of the transformer shorted to the case the breaker would not blow. Ditto to a metal hull. Whereas in that scenario if we are plugged into shore power the AC input breaker trips because the shore side ground is if memory serves (need to check ABYC) normally connected to the isolation transformer case.
The big question I have left in my mind is do these portable generators connect the neutral and ground conductors together when they start? That’s a really vital issue and if the answer is yes, it solves the above issue, I think, but only for an isolation transformer equipped boat.
Bottom line, I need to think a bunch more about this, and draw it out too.
The above scematic was left to me by the previous owner who I believe was an electrical engineer and might help with your thinking it through. I have a selector switch installed to choose between 110 generator, 240 shore, or 110 inverter. I only get dual voltage on shore power. It looks like the boat side earth runs through everything, but doesn’t explain the generator before the inlet.
Nice drawing but it does not tell us anything about this issue. I’m perfectly comfortable with my understanding of ground referencing for a non-portable generator, shore power, and an inverter, which is what the drawing shows. What I need to think on is the use of a portable generator plugged into the shore power lead. By the way, if you want to understand ground referencing better the best drawings I have found are in the ABYC recommendations. They certainly clarified my understanding.
Hi John, actually this is the drawing of the set up for a portable generator through shore power, which is the set up I have. There is a selector switch, as per the dotted box, but I’m unsure if this does anything to the earth when moved from shore to generator.
Does that mean that the generator bypasses the isolation transformer? If so I really don’t like the look of this at all.
Bottom line, I just can’t get into solving these kind of issues on an individual bases. I will think, and posible write about using portable generators, but that will take some deep research and not a little thought.
Sorry, but I wouldn’t really recommend this setup.
First, when using the genset (1,3) according to the drawing there is no ground fault line at all, or at least the GF line emerging from the transformer is not shown.
Next, the genset feeds into the transformer secondary. If this is an “old school” transformer based on windings on an iron core this is bidirectional, so the genset would induce current on the shore side of the transformer, which would power the (possibly open) shore plug. A dangerous situation.
In case of a modern HF transformer it would most probably burn the electronics, or at least trigger the internal breakers.
Why not power the transformer from the genset? this would circumvent these issues.
A very good point that I had not thought of about the induced current on the shore side with that set up. Really scary given that north America boat shore power sockets, are male!
Hi Ernest and Dan,
One thing that Ernest and I may have missed is that it looks like the previous owner has installed a selector switch that might be to code and only connects one source at a time, then Ernest’s worry about reverse feeding the isolation transformer goes away.
If that’s true this installation might even meet code. The key will be to trace out all the wiring and make sure it conforms to either ISO/CE or ABYC particularly in the area of when and where the neutral and ground are connected together and to the boat’s bond system (ground referencing).
To put it another way, at least in theory, I think (don’t know), that if the portable is wired in exactly the same way as a fixed generator with all code requirement met, then there would be no difference between it and a fixed generator as far as shock safety is concerned.
The problem is going to be finding someone with the deep theoretical and practical knowledge to verify that. Only that kind of person on the boat can verify that this set up is safe, all else is dangerous speculation.
I have to say that I’m nervous about this non standard installation, particularly around ground referencing since the diagram does not make that vital area clear and further seems to indicate that the generator is on the secondary side of the transformer, but you are saying that the generator runs through the transformer. And now that I hear that there was mixing of UK and and US standards I’m doubly nervous. Just way too much ambiguity here.
Bottom line I stick by my original recommendation that the whole thing needs to be traced out carefully and then brought into line with either ABYC or ISO/CE.
Sorry, I know that sounds like a liability-fear driven cop out, but it’s not that at all, but rather serious concern.
Thanks, I fully appreciate how difficult it is to give an opinion on something from a dodgy sketch and a bad description! If nothing else this exercise has made me think about and look at the AC side of my boat considerably deeper than ever before. Knowing how it works in practice, I do now have a reasonable level of confidence that it is doing what it is meant to, whether it meets AS/NZ code may be a different question. I work with a bunch of marine electricians, so will ask one to take a look; though if you ask the same question to 5 electricians you’ll get 6 different opinions…
John, a portable generator delivers no “neutral” but merely two phases with 120V (or 240V) potential difference. One of these phases is usually connected to the ground fault connector(s) at the gen plug(s), but this only helps if the gen and whatever is plugged in share a common “ground” where a fault current can pass between gen and its client.
Some gens come with a ground hook you’re supposed to drive into the ground but this might be unwise to do on a boat. So the only way to use a portable gen for general onboard AC is as you say via an isolation transformer (wired correctly).
Similar issues arise with inverters, but I won’t cover them here 😉
Not if it’s a single phase generator, although I do agree that the concept of “neutral” is dependant on ground referencing.
On your idea. I agree, less than ideal, but I doubt that we will get RF hum given that the cable is shielded. Also, it would only be a problem when plugged in, when we will not need the VHF anyway. Still, a good point to keep in mind when running cables.
I am absolutely unqualified to make comments about safety of electrical systems, so that’s exactly what I’m going to do now.
Looking at that photo, I’d be worried that there seem to be AC and DC conductors passing through a bulkhead not protected from chafing and not isolated from each other by a conduit.
Good point to check, but there is chafe protection on the AC lines (spiral wrap). I don’t think that conduit is required but I will check ABYC.
> 126.96.36.199 When AC and DC conductors are run together, the AC conductors shall be sheathed, bundled, or otherwise kept separate from the DC conductors.
I guess this means a conduit is not required. Told you I’m unqualified 🙂
Thanks, but you also got the fact that they should be separated from DC. Of course what the heck does “separated” mean. Seems like most everyone assumes that the sheathing does that. Certainly I have never seen a boat with significant real separation.
Dear John and Vesa,
Currently in the final stages of updating our entire charging AC/DC, storing and monitoring systems. (1988 Swan 53) I have been informed by our ABYC designer and installer that with our Victron isolator, along with a residual current device (RCD) or a ELCI will suffice to meet Victron’s design and installation standards. ( we have an RCD)
While I’m sure your installer is correct, if it were me on a boat of that size, and probable complexity, I would definitely go up to an isolation transformer and then move the ELCI to the boat side output. There are just so many benefits in both function and safety, and the cost will be a small fraction of what this is costing you overall.
Perhaps I was not clear we did install an isolator transformer and have an RCA boat side. I believe RCA/ELCI are basically the same? For sure my personnel weak points have been the refitting the electrical systems and have relied on outside boatyard assistance. Which as you correctly point out do not always have my best interest and safety in mind. RANT……. I am consistently riding them on taking care of these details, which for what I am paying they should be managing themselves. P.S I hate them all 😉
Good to hear, but it brings up another worry (sorry to add to your hate) if you have an isolation transformer you don’t need or even want a Victron isolator. If your installer does not know that his whole installation design should be checked over against ABYC recommendations.
PS: Right now I hate everyone single person in the marine industry.
Really! I would like to know more to the subject. I thought Isolator Transformers are fairly straight forward. https://www.victronenergy.com/isolation-transformers/isolation-transformers-2000va-3600va-7000va
Further up in the thread you mentions a victron isolator and then said you had an isolation transformer.
Maybe you meant an ELCI and not an isolator?
But if you did mean an galvanic isolator then that’s the worry since any person who installs an isolation transformer and a galvanic isolator in the same boat does not know what they are doing and further more can’t read the ABYC recommendations or ISO code, and even further, has no basic understanding of electrical theory. In summary, said person is a menace because installing an isolation transformer requires completely different wiring.
I would also estimate that a good 90% of boat yard “technicians” fall into this menace category.
For example, there is only two people that I know of in the entire province of Nova Scotia that I would trust to install an isolation transformer, and one is the guy I see when a shave.
I would also estimate that a good half of the isolation transformers out there are wired wrong.
Misspoke; no galvanic isolator only isolation transformer. For sure eliminates the need for galvanic isolators and polarity alarms.
Good to hear.
It never ceases to amaze me how screwed up isolation transformer wiring can be on brand new boats. The problem is that most boat yard techs have no real theoretical electrical understanding and are installing stuff monkey-see, monkey-do, so they just don’t understand why a galvanic isolator is not required if an isolation transformer is present. I have also seen isolation transformers on brand new boats wired wrong so they are not in fact isolating. I wrote more above about the terrible lack of training in the marine industry.
Also to the shore side connection we have gone with the SmartPlug https://smartplug.com/ Which as understand is a vast improvement in shore power connection and safety.
Now I have to piss in your bilges.
you don’t mention polarity although this is as well important.
I just refitted the complete AC system on my boat after purchase, and installed a Philippi polarity monitor. The AC master switch has two “ON” positions, where “1” passes phase/neutral unmodified, and “2” exchanges phase/neutral. So if you come around an incorrectly wired post the monitor would show red instead of green, and all you have to do is to use master position 2 instead of 1.
Actually I mention polarity testing not one but twice in the above article.
Also, I think, if it were me, rather than installing a switch like that with attendant danger of making a mistake with it, I would just install an isolation transformer since once you have one polarity is set on the boat so the dock polarity no longer matters.
Uh, well, I should make a habit of not skipping parts of the article – of course you did, I just skipped that expensive BlueSea monster 😉
Of course you’re right in pointing out that a mistake can be made, however this would immediately show up in having the polarity monitor being bright red instead of green, cannot be overlooked as the monitor is located immediately above the switch. Additionally this monitor shows if the ground fault wire is connected correctly – if there is no connection both lights (red&green) are illumniated simultaneously. If this is the case my governance dictates that AC must not be switched into the cabin, but the chargers (being fully isolated and having no ground fault line anyway) can still be used.
All this for less than 50 bucks if I remember correctly.
Hi Again Ernest,
Added to the above, since you have a metal boat, my recommendation of a transformer goes double and then when you sail to Canada to see us, you will also be able to plug in—I’m going triple on that recommendation.
Just need to rearrange miscellaneous structures (such as the engine) to make room for that… 😉
Seriously, I did consider (in fact still am) but at the moment there are more important things on the list, the AC system being thoroughly tested and ok’ed for now.
Check out the Mastervolt, so small and light I’m considering one for the J/109.
A year and a half ago we paid only $720 (USD) for a Victron isolation transformer (3600W). Worth every penny. The Victron transformers also do voltage conversion (115<->230V) which, at the time, the Mastervolt isolation transformers did not.
Great to hear that you were able to get one for such a reasonable price, particularly when we take into account that buying one means we save about $300 on a galvanic isolator. Also I love Victron’s stuff, well designed and great quality.
I guess I would still consider the mastervolt since it’s lighter and smaller, but that’s a function of having a very weight sensitive boat.
I’m going to have another guess: is it that the equipment appears to be in part of the bilge, which is a really silly place to put electrical equipment?
Looks like up under the deck-hull joint to me. But if it’s the bilge, then oh, boy…
Could be right, in which case I change my answer to that centre bolt appearing to be galvanised and starting to corrode. As well as the entry gland for the breaker being at the top and right under above mentioned dodgy bolt.
Bingo! You get the tee shirt. It’s the entry glands at the top of the box, and to make it worse they are right under the bolts for a stanchion base that could leak, and she came from the factory like that. For shame Tillotson Pearson!
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Yup, all true, and all fixed now with the Blue Sea box and breaker I installed. That said, I don’t think a reverse polarity lock out is required by ABYC, just an alarm light, but I would have to check to be sure—good idea though.
Re the photo, the shore power leads are resting on a bolt end and unprotected, not a good scheme.
The shore power for our boat, an elderly Irwin 37, come aboard and goes through a hydro meter. From there it goes to two things, the battery charger and the hot water tank, all else is done through the inverter.
What is a “hydro meter”? Also note that the water heater is one of the highest shock risk AC items on a boat so the AC should still have a ELCI and it would also be a good idea to have one on the output of the inverter.
Ah wait – did you say you’re running the calorifier from shorebased AC, and the rest of the boats AC from an inverter?
I’d say this is inherently not ok except when you NEVER use the inverter when docked and plugged in, ’cause a fault that would connect shore power with your inverter wouldn’t be desirable.
Basically the rule is to never have more than one single source of power, the others inaccessible by design.
That’s true, except that inverters have a pass though relay that pulls when on shore power, and at the same time disables the inverters ground referencing. Of course that depends on the inverter being wired right.
This is true for combined devices (charger/inverter), but a “normal” inverter hooked to the battery bank has no idea if there is shore power live or not. Therefore strict provisions must be taken so the inverter can only be started when shore power is completely disabled.
Additionally: with shore power (w/o isolation transformer) the ground fault line must be connected to bonding when shore power is active. This connection MUST NOT be in place when the inverter is running, usually the inverter case will be “grounded” then (depends on the inv make).
I agree, but the bottom line is still wire the boat to ABYC or ISO/CE not the comments at AAC or even articles written by the editor and publisher.
Again an important topic that is almost neglected in most boats. I’ve made sure all this is good on our boat, but have no isolation transformer, yet. It’s an interesting topic. I see Steve D’Antonio and others have also pointed out that a lot of isolation transformers are installed in dangerous ways, especially how they may effectively disconnect the boat from the shore ground system, without a good alternative.
I’m not yet comfortable enough with my own understanding of the topic to make a decision, but I consider getting one of the Mastervolt isolation transformers you mention. Looking at their texts and data I get some (maybe unfounded) questions. In their first sentence of the description they use the words “galvanic isolation”, which is a whole other thing than an isolation transformer, of course. The product name is “Mass GI 3,5”, where I assume GI is for galvanic isolator?
I also notice that Mastervolt has another product with the same capacity that weighs in at 5 times as much, 30 kilos, even though that one is a stripped version, no cabinet etc. There one can visually confirm that it’s an actual transformer with coils and all. They still use the same words in their description, though. Galvanic isolator.
Is this a case like when the old type battery chargers with coil transformers were replaced by electronic transformers with dramatically reduced weight and size, plus far better performance? Or is it two different types of product confusingly put in the same group because they are applied to the same type of problem, galvanic corrosion prevention?
Hi Stein, of course an Isolation Transformer galvanically decouples the boat from shore as well. The GI 3.5 and GI 7 are in fact full blown isolation transformers and differ only in power.
The issue is that a transformer can be used in two different ways (isolation or polarization), and this is often grossly misunderstood – for our requirements full isolation mode is required.
There is one drawback in using an IT, being that the shorebased line passes through the boat but is not grounded in the boat (must not!), so a fault in the supply line aboard before reaching the IT can wreak havoc. Actually this is the reason why the supply line must have an ELCI + breaker as close to the shore plug as possible to minimize such a risk.
What I wondered about is the difference between the GI 3,5, and the IVET 3,5. They both have the exact same output, 3,5 kW: https://www.mastervolt.com/products/e-core-without-cabinet/ivet-35/
Since they are both touted as isolation transformers and both description texts seem to say, vaguely, that they work mostly the same way, I wonder why one weighs 6 kilos, and the other weighs 30 kilos, 5 times as much as the other while giving the same 3,5 kW power. The latter heavier version is even in a “naked” edition, without the slow start included.
My only way of explaining this is that either they are:
– Different types of tools doing a different job.
– Different generations of tech doing the same job.
– Some other explanation?
I’m no expert but – same job, different tech. The GI 3.5 is a modern high frequency switching converter while the later is an old school iron core transformer. Interesting to me is that the GI 3.5 will only put out 1.9kW @ 120V because it is limited to 16A.
I agree with the first part of your answer, but not the second. In fact the shore based ground line is only grounded on the isolation transformer shield.
So, as long as the isolation transformer is installed right it pretty much does not matter what faults are on the shore line, including a broken ground or reverse polarity. That’s one of the beauties of isolation transformers and why ABYC exempts isolation transformer boats from having an ELCI on the supply side.
That said, I agree that having an ELCI on the supply side certainly can’t hurt and could save us in some circumstances.
Of course you’re right John – however I meant the line from the shorepower plug on the hull to the inverter. This is basically ungrounded shore AC and must be treated as such, thus the “ELCI as close to the plug as possible” recommendation/requirement.
Usually it is sufficient to have this cable completely sheathed from plug to inverter (except the ELCI connections of course).
I’m closing the comments on this post since we are starting to veer off into advising members on complex subjects around AC.
The bottom line is that our boats need to be wired to either ABYC standards or ISO/CE by someone qualified to read and understand those standards and the associated recommended circuit diagrams.
My intent with this article was to point out several dangers that I found on a new boat and explain how I rectified them as well as recommending that we all as owners have a responsibility to make sure our boats conform to standards.
My intent, as I wrote in the summary, was not to write a guide to AC wiring or moderate the creation of one in the comments. ISO and ABYC have already done that task way better than we ever will.
That said, the discussion has taught me plenty, been useful and has exposed what I think is a dangerous practice of using portable generators to power our boats. I will think more on that and do some research and if I can really get it clear in my own mind, write more.
One more thought before I close this.
Thanks to all of you who contributed, particularly Earnest, Matt, and Vesa who confirmed some things I was not certain of and pointed put things I had not thought of.
I have reopened the comments to this post. If nothing else, I needed a bit of time to really think about the issues raised.
That said, please do not veer off into giving advice on how AC systems should be wired. The bottom line is that all boats with any high voltage aboard should be wired to either ISO/CE or ABYC, not the AAC comments.
Also, please be careful about stating things as fact. In the words of someone (not clear who):
Keeping that quote in mind was a lot of why the original version this article included a request for independent verification that a ELCI would trip even if the shore ground was disconnected, even though I clearly understand how ELCIs work and was near-certain that was the case.
Finally, please keep in mind that this is not just forum-fun, we are dealing with life threatening voltages here.
That’s a very good point that installing an ELCI can find dangerous faults that may have been there for years. I’m just finishing off the installation of the ELCI on our boat and won’t be at all surprised if it trips the first time I power up and I end up trouble shooting some problem.
For your sanity, I hope not. What lead us to finally suspect the Rotary selector switch as the problem, was Not being able to clear the fault by isolating any of the Panel circuit breakers. I wish you better fortune.
Thanks. The good news is that this boat has a very simple system with no selector switch and no inverter, so anything that trips the ELCI will probably be fairly easy to trouble shoot just by turning on breakers one at a time.
One hint if the ELCI trips immediately after powering on and plugging something in:
check that the neutral wire (the complete circuit) actually runs back through the ELCI. I have seen it happen several times that a device that has its live wire fed through the ELCI has its neutral bypass the ELCI, thereby making the ELCI trip as it sees a current imbalance.
This typically happens in distribution panels where some devices are fed by an ELCI/GFI and some directly from a circuit breaker with no GFI, with separate neutral busbars for each circuit but with one neutral wire connected to the wrong neutral bus, so this should not happen on a boat with an ELCI upstream of all AC distribution, as all neutral wires should terminate at an ELCI or a single neutral busbar connected to one.
Still, this situation might be tricky to troubleshoot, since it is really not a dangerous fault although the ELCI will make it seem that way (no device is broken or miswired, and you are not at risk, it’s just nuisance tripping the ELCI the second you connect something to the receptacle).
In this scenario the ELCI trips when you plugin a device that consumes power in any receptacle downstream of it, but it should not trip by merely plugging in the shore power cord with all consumers disconnected.
That’s a good point. Of course such a thing should never happen with a properly wired and organized panel(s) but we all know how boat systems get patched and added to over the years. In fact with my last two boats (before this one) the AC system was such a patch work I just tore the whole thing out and started again, by far the best and safest bet.
Wow. What I don’t know could hurt me. The through hulls on my boat are not bonded. I have considered doing that, but it is quite a task. It sounds as if a good first step, nonetheless, is to have a certified electrician install an ELCI. Thanks.
Re: portable generators. As John noted they can be used at houses when fitted with a change over switch to connect neutral to ground. In a marina the ground connection is somewhere on shore, which is why the inverter charger has relays that connect them when in invert mode, but disconnect and pass through in shore power mode. From the Victron Multi user manual:
The MultiPlus is provided with a ground relay (relay H, see appendix B) that
automatically connects the Neutral output to the chassis if no external
AC supply is available. If an external AC supply is provided, the ground
relay H will open before the input safety relay closes. This ensures the
correct operation of an earth leakage circuit breaker that is connected to
Our solution back in the days when we had a portable generator was to take a plug from the hardware store, jumper white to green and plug that into the receptacle on the generator. This provides the grounding that ordinarily occurs somewhere on shore. The indicator that this was needed in our case was the reverse polarity light flickered without the grounding plug in place.
However I will provide the same caveat – I’m not a trained electrician or electrical engineer, so it’s possible, if not likely, that there is some reason this is a bad idea. As others said, the isolation transformer is a more fool proof solution.
Interesting. I have just finished an article on this whole subject. We will be publishing it in a few days.
One other point – newer marina installations in the US have ELCI’s or Residual Current sensing breakers in the shore power pedestal. The new section in Fort Pierce FL had those and routinely had boats come in that would trip them. Our brand new Outbound 46 did, and an electrician finally traced it to a sliver of metal left between the neutral and ground connections on the water heater (which looked to me like a manufacturing artifact to prevent welding current from going through the heating element). And this was a well respected first world brand. We were fortunate to discover that early in our ownership of that boat.
Wow, that really brings home the effectiveness of ELCIs! Without you finding that issue, highlighted by the ELCI trip, the green wire could have been carrying current for years without you ever knowing.
Great article thank you! Like probably a lot of us, I am a total newb in electrical boat system. Can you recommend some great book to learn from the start ?
Good question, but given that I have training, I tend to just go directly to the ABYC recommendations and implement those so I have not read a lot of books.
That said, you can get the important basis in the first three chapters of our online book: https://www.morganscloud.com/category/electrical/online-book-electrical-systems/
After that I cover most things you will need to do in detail in subsequent chapters.
You might also want to read just about anything by Nigel Calder. Start with this one: https://www.amazon.ca/dp/B006QA720O/ref=dp-kindle-redirect?_encoding=UTF8&btkr=1
I have also heard good things about the 12 Volt Bible.
Anyone else have any recommendations?
I use a socket test plug at the marina post before I connect. This avoids the danger of connecting to a faulty or reversed supply and having to get back on the boat to check what the panel is telling you.
I also plug my own inline RCD at the post and plug my coord into that. This not only protects the boat but also if the insulation on the cord is damaged and someone stands on it with wet feet on the dock.
Finally I plug in the socket tester in the boat to confirm all is ok.
Of course you still have the issue of needing to prove the correct operation of your tester, so perhaps a second for an periodic check.
Sounds like a good plan. Could you link to a source for the socket tester you use, please?
Hi John, here is a link for the one I use at home, although I have an american boat it was supplied to the UK so is kitted out with 13 amp 3 pin sockets. These test plugs are available in all pin configurations in whichever country your boat is from.
I would presume this would Identify a fault in a galvanic isolator (open circuit) when used in an onboard socket?
Looks like a good tester, although fully evaluating something like this is way past my pay grade, particularly without getting my hands on one.
I did have a quick read through of the EZ365 and it looks like it will be a very useful test before plugging in.
As to whether or not it would detect an open circuit isolator, I’m thinking yes, but would not guarantee it.
On the other hand I’m fairly sure that it would not detect a shorted isolator.
One other thing is that the manual warns of inaccuracies:
An isolator is capacitive device, so that may be in issue for accuracy, so I would still check the continuity of the ground connection from the isolator through to the end of the unplugged shore power cable with a meter occasionally.
All that said, this looks like a worthwhile device to own.
We have just been working through electrical system checks and improvements on a second-hand 38 foot yacht (1986) we purchased. Shore power connector was loose (replaced it), some wiring in 12v DC system had been connected with electrical tape in past DIY repairs (had a marine electrician crawl over every wiring join and do it properly), we had a 240v compliance test done (we are in Australia) – all passed OK and feel like we can sleep at night knowing it’s all correct. Now checking re situation on galvanic isolator as still learning – that’s the next job and will probably have new one installed. We don’t keep the boat plugged in to shore power when we are away – solar power keeps batteries topped up for bilge pumps and fridge, everything else switched off. Although just about to install a BRNKL also to remotely monitor certain systems.
My Hinckley had paired 30 amp shire power cord systems. One for AC, the other for everything else. Each is connected to a vectron 3600 isolation transformer
We plan a transatlantic from Bermuda after the 2022 race to azores and in turn to Scotland
Where did you source and supply shore power cords for UK and EU for dock hookup?
Mid-Atlantic Yacht Services in Faial will be able to do and/or supply most anything you want along those lines. Contact ahead of time for assurances.
If planning to be there for period of time: we had a small EU/UK power panel installed with circuit breakers for 2 receptacles and a battery charger (using a full range of voltages and hZ). I also had a EU/UK shore power inlet. This allowed use of local appliances such as de-humidifier (very nice as you live closed up more than many cruising locations) and space heaters. It simplified living and cruising on the boat during our years in Europe/UK a great deal.
My best, Dick Stevenson, s/v Alchemy
Before we left for Europe I bought a couple of 30 amp female sockets that would mate to the plug on the end of our shore power cord. When we got to England I bought the required male plugs to go into the plug on the dock and made up a pig tail adapter. Then all you need to do is change the taps on the transformers to step 220 volts down to 110 and you are good to go.
Just make sure to check that all of the gear you use with this set up can operate on 50 Hrz since the transformers don’t change that.
Re “testing ground continuity” – there is a really smart little gadget from Philippi that will show you immediately if your shore power connection is fine (green LE), reverse polarity (red LED), or if the ground connection is missing or has failed somehow (both LEDs).
That does look like a good gadget to have. Much better than a single reverse polarity light.
I have called ABYC and they report no membership below $275 USD per year, a “business membership” and no individual membership at $190/year. Did I miss something?
And even at $190/year, I do not suspect I would wish to consult the standards more than a handful of times.
I do very much want to support ABYC and I make a point of asking every boatyard I come into whether their techs are ABYC certified and think it would make a difference if everyone did this.
My best, Dick Stevenson, s/v Alchemy
Sounds like the right hand does not know what the left is doing: https://abycinc.org/mpage/becomeamember
Sure does. Thanks, Dick
A follow up on ABYC membership:
I twice reached by phone the ABYC membership coordinator who kept saying there was no membership for boat owners. Earlier today I have talked with her and she has now acknowledged the recreational boater’s membership for $190 per year. Not sure still what the confusion was.
There is an industry vs recreational tree/crossroads to their web site and the default seems to be industry oriented and that was another rabbit hole I kept inadvertently going down. So I ended up on the part of the site which, of course, did not address recreational boaters.
Thanks for the help.
My best, Dick Stevenson
I have a thirty year old boat that was completely re-wired 12 years ago. Unfortunately, they never included a galvanic isolator or a ELCI in that project, so I’m looking to correct that now.
Thinking about how galvanic isolators are sized, they are designed to take the complete fault current until the main or sub breaker trips. That means a 30A breaker should have a minimum of a 30A isolator. But with a ELCI installed, the ground wire should never see more than 30mA before the ELCI trips, so sizing a galvanic isolator for 30A is an overkill and waste of money. Thoughts?
I guess that could be true, but what if the ELCI fails? And what would the real savings be? Not much I’m betting, so my thinking would be why take the risk of unintended consequences? There’s also the issue of deliberately going against code with the attendant liability if someone gets hurt and the probability that a surveyor would flag the issue at resale.
Just checking on naming as it took quite a lot of googling.
Am I correct that for Europe (well at least the UK) when you talk about ELCI breakers that is the same as RCD breakers that we use?
If I am correct would it be possible to add a note to the text as searching for ELCI products in the UK doesn’t find much.
Bottom line, I don’t know for sure, and after Ernest’s experience I’m loath to recommend anything that’s not from a vendor I trust like BlueSea. That said it does seem that the two are roughly the same, although the R stands for residential which does not fill me with confidence for use on a boat.
I did find this: https://www.boats.com/how-to/whats-difference-elci-rcd/
The author of that article, Ed Sherman, has real chops and credibility in this area.
Anyone else know more?
John, late to the party on my read of this but better late than never. I just resubscribed , thanks. In your article you test continuity of the shore ppower ground. You state “ from the ground pin on the unplugged dock end of the boat’s shore power plug to the shore side lug on the isolator. “. My new galvanic isolator , just like yours, is installed in a stern locker accessed below through my aft cabin. How do you physically “ connect your meter” between the shore side lug of the isolator in the aft cabin locker and the ground pin on the boat’s shorepower socket which is located on the outside aft bulkhead/ stern scoop . These twopoints are just feet apart but separated by the deck ! I am sorry i am either ignorant or misunderstand your instructions.
I probably was not clear enough. The trick is to plug in the shore power cord and then take the shore end below with you to the isolator. The added benefit is that this way you are also checking the ground continuity of the shore power cable itself.