Interesting Point of View From Nigal Calder

[guyrj33]

Let’s not forget that ABYC is a business. Their business is selling standards. They will continue to invent new and more complicated standards. To insure they have new products to sell.

[smac999]

The issue is having enough charger power. You’d want 200-300a to keep up with ac Inverter loads.

Probably even more if running air conditioning.

I would only do this if traveling to different power countries. Which 99% of boats will never do.

[_LifeInTheWild_]

This may add some perspective to my situation. I am a 30' Allied Seawind ketch. I am redoing the electrical because the boat was a floating fire bomb. This is what I have so far:

2x 6v 210ah golfcart batteries

Promariner Prosport 20a charger

Victron battery isolator

Elci Ac breaker

1500w inverter

40a alternator

I am on Lake Superior. I have basic cabin lights, nav lights, GPS, radar, bilge, radio, and a couple other small draw things. I don't have a fridge or windlass. I love simple. My usage will be some overnights in the Apostles for now. I will be adding 200w of solar this summer at some point. My AC usage will be device charging and a small blender.

I feel that an inverter based system makes sense to me and if I can skip a galvanic isolator and not have to worry about stray current coming from my system I will be a happy sailor.

[s/v Jedi]

Installing a powerful battery and inverter is key to get to enjoy modern life aboard

Here is us today, running a 40 gallon per hour watermaker, an induction cooktop and a microwave all simultaneously without shore power, without generator.

Also, once you have an isolation transformer, you can safely use it’s output power aboard, as long as it’s connected correctly, unlike ABYC wants it.

[boatpoker]

Originally Posted by parachute

If you don't fit a galvnanic islolator then you risk stray current corrosion which will destroy everything electrical.

You need to do a little more reading. Stray current corrosion and galvanic corrosion are two different processes

[boatpoker]

Originally Posted by guyrj33

Let’s not forget that ABYC is a business. Their business is selling standards. They will continue to invent new and more complicated standards. To insure they have new products to sell.

A "not for profit" business to be fair.

[smac999]

Originally Posted by Dsanduril

As Nigel notes, it is not ABYC compliant, so if that is important to you (or your insurer, or a surveyor, or.....)...

A shore power inlet to rcd breaker to battery charger is certainly abyc compliment. So would the inverters if wired correctly. There is no requirement to have an isolation transformer on a boat. So I’m not sure which part is not...

[_LifeInTheWild_]

Originally Posted by smac999

A shore power inlet to rcd breaker to battery charger is certainly abyc compliment. So would the inverters if wired correctly. There is no requirement to have an isolation transformer on a boat. So I’m not sure which part is not...

I believe the part that the ABYC has an issue with is omitting the AC to DC grounding connection thus taking care of the galvanic corrosion issue.

[Lake-Effect]

Originally Posted by s/v Jedi

Also, once you have an isolation transformer, you can safely use it’s output power aboard, as long as it’s connected correctly, unlike ABYC wants it.

I'm currently studying to write the exam for renewal of my ABYC Electrical cert, and today I did the Inverters and Isolation Transformers section. For real. So thanks OP for the review question!

I didn't see anything to suggest that the ABYC guidelines for installation of isolation transformers creates a galvanic current path (ie no, they don't tie the iso transformer's case to both the AC ground and the boat's DC ground. Just the latter. They show some sort of shield on the primary winding that gets connected to AC ground. Wonder how that sits with UL...). This is of course out of a book; is there something about the available isolation transformers that creates a problem achieving this?

I did read the highlighted part of Nigel's commentary; only fly in the ointment that I could imagine is if the charger's negative DC out is internally tied to its AC ground. Easy enough to measure with an ohmmeter.

[s/v Jedi]

Originally Posted by Lake-Effect

I'm currently studying to write the exam for renewal of my ABYC Electrical cert, and today I did the Inverters and Isolation Transformers section. For real. So thanks OP for the review question!

I didn't see anything to suggest that the ABYC guidelines for installation of isolation transformers creates a galvanic current path (ie no, they don't tie the iso transformer's case to both the AC ground and the boat's DC ground. Just the latter. They show some sort of shield on the primary winding that gets connected to AC ground. Wonder how that sits with UL...). This is of course out of a book; is there something about the available isolation transformers that creates a problem achieving this?

I did read the highlighted part of Nigel's commentary; only fly in the ointment that I could imagine is if the charger's negative DC out is internally tied to its AC ground. Easy enough to measure with an ohmmeter.

ABYC apparently wants to see some obsolete type of transformer with a shield around it’s primary winding. Never seen anything like it, but with the toroidal transformers as used by high end manufacturers this is not possible and they come up with stuff too stupid to believe: defeat the isolation transformer by connecting shore ground to boat ground. It puts tears in my eyes, first from laughter but then crying as I start to realize they are serious. It’ll take a couple more years before they see the light, like they did with ground fault RCD devices (iirc it took 10 years with that one though ).

Smartest thing to do is buy a reputable isolation transformer and connect it as manufacturer recommends, then to be sure use a multimeter to confirm that shore ground is not connected to boat ground

[Lake-Effect]

Originally Posted by s/v Jedi

ABYC apparently wants to see some obsolete type of transformer with a shield around it’s primary winding. Never seen anything like it, but with the toroidal transformers as used by high end manufacturers this is not possible and they come up with stuff too stupid to believe: defeat the isolation transformer by connecting shore ground to boat ground. It puts tears in my eyes, first from laughter but then crying as I start to realize they are serious. It’ll take a couple more years before they see the light, like they did with ground fault RCD devices (iirc it took 10 years with that one though ).

Smartest thing to do is buy a reputable isolation transformer and connect it as manufacturer recommends, then to be sure use a multimeter to confirm that shore ground is not connected to boat ground

Thanks for that info.

One thing that I hadn't fully grokked til this afternoon is what was meant by "polarization" vs "isolation" transformers. I hadn't heard that terminology before. Apparently the only difference is that a "polarization" transformer has its case connected to both AC (shorepower) ground and boat ground... and an "isolation" transformer's case is only connected to boat ground. In other words, the difference is in their conections.

This article from Steve D'Antonio provides a good overview. For me, anyway.

[CharlieJ]

@s/v Jedi #25

ABYC apparently wants to see some obsolete type of transformer with a shield around it’s primary winding. Never seen anything like it, but with the toroidal transformers as used by high end manufacturers this is not possible and they come up with stuff too stupid to believe: defeat the isolation transformer by connecting shore ground to boat ground.

Here we go again.

1. The isolation transformer in the ABYC Standards is far from “obsolete”.
2. The electrostatic shield is not “wrapped around its primary winding”...it is placed between the primary and secondary windings and is tied to the shore safety ground. So it is no surprise that you have never seen anything like it.
3. Toroidal isolation transformers are currently being reviewed. And, BTW, there is an Italian manufacturer that makes a boosting toroidal isolation transformer that is fully compliant with the ABYC Standards.
4. The shore safety ground is not tied to the boat safety ground in an ABYC compliant installation with an ABYC compliant isolation transformer.

Other than these points, you are spot on.

[CharlieJ]

@guyrj33 #16

Let’s not forget that ABYC is a business. Their business is selling standards. They will continue to invent new and more complicated standards. To insure they have new products to sell.

You are terribly mis-informed about the workings of the ABYC.

First of all, ABYC is a non-profit organization with a paid staff of about 17 people. The Standards are produced by about 350 volunteers in various Project Technical Committees according to discipline. The PTCs are made up of boat builders, surveyors, UL, USCG, marine equipment manufacturers, marine electricians, etc. and is very closely controlled so that no segment becomes dominant.

The PTC meetings are open to the public and anybody that is interested can be put on the mailing list to be informed when a Standard is going through the review cycle. Any interested person can comment on a Standard, propose changes, and take part in the meeting to resolve the comments. Any interested person.

The Standards are reviewed periodically to ensure that they are in alignment with technological changes. As a case in point; HF isolation transformers do not have an electrostatic shield. Their construction and certification were reviewed, and it was determined that they did not require an electrostatic shield and the applicable Standard was revised to accept them. This sort of review and change does not occur immediately, remember the PTCs are made up of volunteers with day jobs.


Hopefully this clears up you misconceptions regarding the ABYC.

[s/v Jedi]

Originally Posted by CharlieJ

@s/v Jedi #25

Here we go again.

1. The isolation transformer in the ABYC Standards is far from “obsolete”.
2. The electrostatic shield is not “wrapped around its primary winding”...it is placed between the primary and secondary windings and is tied to the shore safety ground. So it is no surprise that you have never seen anything like it.
3. Toroidal isolation transformers are currently being reviewed. And, BTW, there is an Italian manufacturer that makes a boosting toroidal isolation transformer that is fully compliant with the ABYC Standards.
4. The shore safety ground is not tied to the boat safety ground in an ABYC compliant installation with an ABYC compliant isolation transformer.

Other than these points, you are spot on.

The important point is that ABYC will come around like they did with RCD devices. They just take 10 years extra compared to the rest of the world. When I was actively designing electronics... in the ‘80s, I already selected toroidal transformers over shielded ones for high end applications so that is why the manufacturers moved to toroidal and consider the rest obsolete for these kind of applications.

I find it funny how people can defend archaic standpoints from ABYC as if those are safer compared to other institutions who adapted new technologies faster. Because that would only make sense when ABYC would put their heels in the sand and keep it that way... but they don’t, they do adapt the new technology, confirming it was the better way to go all the time.

[ranger58sb]

Originally Posted by BillKny

Chris,

You apparently do not understand the nature of the system, or the capabilities of modern inverters.

A shore power connection for a typical yacht of the size we talk about here is either 30 Amps/120V (roughly equal to 16 Amps/220V) or 50 Amps/120V (roughly 32 Amps/220V). This can be exceeded for very short periods of time for motor starting and such, but in general the continuous duty rating for these systems is 85% of rated load, or 26 Amps (3000 W) or 43 Amps (5000W).

This kind of continuous load is easily driven from inverters. If you wanted a buffer, you could install a 5kW inverter instead of a 30Amp shore power connection, or a ganged pair of 5kW units instead of a 50 Amp shore power connection.

The real beauty of the system is that you can use the batteries to fill in the peak power draws. We run two 8000 BTU AC units on a 3kW inverter without an issue. If we felt the need to run a water heater on the same system we'd have installed a 5kW inverter and all would be fine.

Of course you have to replace the DC power. so you need battery chargers at least equal to the average power draw of the AC system. On our 24V system this is easily done out of a 30 Amp shore power connection with a 100A charger. It's a beast, but it does the job. On a 12 volt system, a parallel pair of 100Amp chargers would probably be better.

There is NO reason you can't have your AC and hot water AND have an all inverter boat. None at all.

I think I understand enough to know it would take boatloads of DC to run aircon (e.g., two 16K BTU units) 24/7 while at anchor... and then a little more to keep the water hot.

I wasn't intending to imply it can't be done... just that there are some additional hoops one might need to leap through (maybe Lithium, maybe solar, etc.) to make it good.

-Chris