Shore Ground NOT Connected to Isolation Transformer

[goboatingnow]

Originally Posted by Lake-Effect

....And more hoops to jump through than a Vegas lion act.[

You haven't considered all paths. How bout a frayed shorepower cable, or a busted inlet? Without a return ground, RCDs etc don't trip (fault remains) until there's a leakage path.

Eh , the installation I described is standard European boat wiring

Exposing a conductor on the shore side will cause the RCD to trip , if a short to earth develops ( through a person or otherwise ) unless of course if your in the US when you’ll just fry until the breaker trips. This has nothing to do with a boat.

Busted inlet , as above

To create a shock there must be some “ return path “ otherwise there is no danger ( ask thousands of birds ) RCDs will trip once any non specific path appears irrespective of the modalities of how it appears.

You are descending into nonsense I’m afraid , of course there is always some bizarre series of unusual events that lead to injury no more then you could trip , fall over the pathetic lifelines and drown. ( or stick two nails into a unprotected US socket !!!)

[goboatingnow]

Originally Posted by Lake-Effect

....And more hoops to jump through than a Vegas lion act.

You haven't considered all paths. How bout a frayed shorepower cable, or a busted inlet? Without a return ground, RCDs etc don't trip (fault remains) until there's a leakage path.

You seem to have forgotten the primary reason why AC circuits and devices include a ground.

[Sigh]
Explain to me why ABYC requires a continuous ground when an isolating transformer is fitted , [/Sigh ]

[Lake-Effect]

Originally Posted by goboatingnow

You are descending into nonsense I’m afraid.

Agreed, this is devolving into daycare for retired yet bored engineers.

I've been on enough boats, transformer-equipped or otherwise, where there are real, not insignificant, risks of electrical shock. Not everyone is GBN or a Jedi! On your boat...

The inadvertent introduction of a third party shore referenced mains fault is extremely unlikely and can be discounted

... I believe you. As a general fact that everyone can safely count on , not so much.

Originally Posted by goboatingnow

[Sigh]
Explain to me why ABYC requires a continuous ground when an isolating transformer is fitted , [/Sigh ]

They don't. I even quoted from their certification manual earlier. They recommend, but agree that the risk is low with iso transformers.

You really are needing hairs to split...

[goboatingnow]

Originally Posted by Lake-Effect

Agreed, this is devolving into daycare for retired yet bored engineers.

I've been on enough boats, transformer-equipped or otherwise, where there are real, not insignificant, risks of electrical shock. Not everyone is GBN or a Jedi! On your boat...

The inadvertent introduction of a third party shore referenced mains fault is extremely unlikely and can be discounted

... I believe you. As a general fact that everyone can safely count on , not so much.

You have two choices

Wrap yourself in cotton wool and never step on board. You’ll never get an onboard shock

Or evaluate the actual risks and develop the solution accordingly.

Third party earth referenced mains is a failure mode I’ve never seen , nor mentioned in the literature of can even reasonably postulate the modalities.

jedi and my point is ABYC takes its cues from NEC which is not boat orientated and is peculiar in its thinking ( as against ISO and IEC ) that peculiarity extends to attempting to correct deficiencies in the NEC code that should be fixed there on shore not on your boat.

Wiring a continuous earth in a isolating transformer situation exposes you to more additional fault modalities not less

[Lake-Effect]

Originally Posted by goboatingnow

jedi and my point is ABYC takes its cues from NEC which is not boat orientated and is peculiar in its thinking ( as against ISO and IEC ) that peculiarity extends to attempting to correct deficiencies in the NEC code that should be fixed there on shore not on your boat.

So we're back to beating on ABYC again. They don't "follow" NEC, they have to operate alongside of it (the "A" in ABYC...) . In terms of electric shock drowning, it might be said that they've attempted to lead or advise the NEC.

Wiring a continuous earth in a isolating transformer situation exposes you to more additional fault modalities not less

The connected ground creates more "potential" (get it??) for galvanic currents and corrosion. This could be considered a fault if it rotted out a through-hull. This problem can be blocked with a galvanic isolator.

What other possible fault modalities would a continuous ground create?

[ranger58sb]

Originally Posted by ranger58sb

We have a factory-installed isolation transformer in our 50A/250V system. Our factory-installed shorepower cord has only 3 wires.

Originally Posted by Sailmonkey

So you’ve got two hots and a ground?

Originally Posted by ranger58sb

I think it's L1, L2, and Neutral. Not sure, though...

I think you're right. I see Hubbell sells 3-wire 50A/250V shorepower cords for use with isolation transformers... and the listing says no neutral.

-Chris

[goboatingnow]

Originally Posted by Lake-Effect

So we're back to beating on ABYC again. They don't "follow" NEC, they have to operate alongside of it (the "A" in ABYC...) . In terms of electric shock drowning, it might be said that they've attempted to lead or advise the NEC.


The connected ground creates more "potential" (get it??) for galvanic currents and corrosion. This could be considered a fault if it rotted out a through-hull. This problem can be blocked with a galvanic isolator.

What other possible fault modalities would a continuous ground create?

It creates a shock hazard between anything making a seawater connection ( inadvertently or not ) and live.

It facilitates impressed current corrosion (a galvanic isolator only blocks small ground currents

It exposes swimmers to shore faults

It conducts earth faults into the boats electrical system ( especially if dc bonded as per ABYC )

[s/v Jedi]

Originally Posted by Lake-Effect

....And more hoops to jump through than a Vegas lion act.

You haven't considered all paths. How bout a frayed shorepower cable, or a busted inlet? Without a return ground, RCDs etc don't trip (fault remains) until there's a leakage path.

You seem to have forgotten the primary reason why AC circuits and devices include a ground.

Your call for this level of safety goes far beyond any other aspect of safety risks deemed acceptable by code. It is imo unreasonable. ABYC agrees with me which is why they made the exception.

I compare it with requiring a measure to save your life in case you shoot yourself in the head. Instead of requiring that, maybe don’t shoot yourself in the head?

The whole world has this figured out, the US will figure it out in the end.

About me calling myself “expert”: I compare myself to the experts working in the committees mentioned and I simply observe that my knowledge goes well beyond most of theirs. Example: they all know how to use a transformer, as well as the principles on which it functions, but I also designed and prototype-built them myself, not just for AC power but also up to VHF radio frequencies. Why would I act as if I am not knowledgeable?

In the past on CF this ridiculing of members who are actual experts in their field of expertise has left very few still here. The departure of especially the naval architects has been a blow to the forum and all because they call BS on members posting stuff that they don’t really know who get pi$$ed off and start throwing personal insults. It simply has to stop.

[Lake-Effect]

Originally Posted by goboatingnow

1. It creates a shock hazard between anything making a seawater connection ( inadvertently or not ) and live.
2. It facilitates impressed current corrosion (a galvanic isolator only blocks small ground currents
3. It exposes swimmers to shore faults
4. It conducts earth faults into the boats electrical system ( especially if dc bonded as per ABYC )

Good effort!

1. How? Continuous grounding (a low-current path to ground) and/or RCD-ish protection mitigates against that shock hazard. Same RCD action as if there was no continuous ground.
2. Galvanic isolators block ANY current until the voltage across the GI exceeds two forward diode drops (approx 1.1 v). Above that, a typical small GI device may be rated for say 50A, but have a surge capacity of up to 100kA). That 1.1v difference blocks all but the most extreme impressed-current corrosion situations.
3. How?
4. Explain, please. Let's not go off-point with the bonded/not-bonded metal issue.

[Lake-Effect]

Originally Posted by s/v Jedi

Your call for this level of safety goes far beyond any other aspect of safety risks deemed acceptable by code. It is imo unreasonable. ABYC agrees with me which is why they made the exception.

Thank you. I respect your opinion. And that you have acknowledged that grounding does offer enhanced safety, but that you consider the benefits of this are so small as to be outweighed by the other considerations, like potential galvanic corrosion. Good stuff. Useful. Complete.

About me calling myself “expert”: I compare myself to the experts working in the committees mentioned and I simply observe that my knowledge goes well beyond most of theirs. Example: they all know how to use a transformer, as well as the principles on which it functions, but I also designed and prototype-built them myself, not just for AC power but also up to VHF radio frequencies. Why would I act as if I am not knowledgeable?

In the past on CF this ridiculing of members who are actual experts in their field of expertise has left very few still here. The departure of especially the naval architects has been a blow to the forum and all because they call BS on members posting stuff that they don’t really know who get pi$$ed off and start throwing personal insults. It simply has to stop.

"Oh Lo-ord it's hard to be humble..."

Most independent experts manage to offer useful information and advice without being absolutist about it, claiming superior authority, or slagging the dominant standards bodies. And making some mistakes, while inferring their infallability. Just sayin.

[goboatingnow]

Originally Posted by Lake-Effect

Good effort!

1. How? Continuous grounding (a low-current path to ground) and/or RCD-ish protection mitigates against that shock hazard. Same RCD action as if there was no continuous ground.
2. Galvanic isolators block ANY current until the voltage across the GI exceeds two forward diode drops (approx 1.1 v). Above that, a typical small GI device may be rated for say 50A, but have a surge capacity of up to 100kA). That 1.1v difference blocks all but the most extreme impressed corrosion situations.
3. How?
4. Explain, please. Let's not go off-point with the bonded/not-bonded metal issue.

Take for example electro drowning , ABYC should really have no input into this as the problem lies entirely with the NEC and the fact that US marina pillars were not fitted with RCD devices.

Hence an isolating transformer with a discontinuous ground simply cannot induce fault currents into the water. Yet an isolating transformer with continuous ground can and does ( and particularly with bonded underwater metals ) as the current can travel through the sea back to the earth ground returning to the boat via the continuous ground to the output of the isolating traffo

Secondly because on boats with sea water there always is a risk of inadvertent ground ( ie sea connected ) faults , a continuous ground actually is less safe then a discontinuous ground as touching metal sea water connected objects does not complete any circuit.

Sorry continuous ground on land , entirely agree , on a boat no , separate fault current returns are best , and ISO agrees with me.

[Lake-Effect]

Originally Posted by goboatingnow

Take for example electro drowning , ABYC should really have no input into this as the problem lies entirely with the NEC and the fact that US marina pillars were not fitted with RCD devices.

Who could disagree that the ISO pedestal solution is far and away the best solution? But the problem exists in N America, NEC wasn't addressing it, and the ABYC would be wrong to ignore it. Especially when a boat industry participant's kid dies from it.

Hence an isolating transformer with a discontinuous ground simply cannot induce fault currents into the water.

The iso transformer reduces the opportunities for putting hot shorepower AC onto a boat's metal and hence into the water, but it does not completely eliminate that risk.

Secondly because on boats with sea water there always is a risk of inadvertent ground ( ie sea connected ) faults , a continuous ground actually is less safe then a discontinuous ground as touching metal sea water connected objects does not complete any circuit.

Not sure what you're trying to say here.

Sorry continuous ground on land , entirely agree , on a boat no , separate fault current returns are best , and ISO agrees with me.

I'd appreciate a cite for that, if possible, please.

[s/v Jedi]

Originally Posted by Lake-Effect

"Oh Lo-ord it's hard to be humble..."

Most independent experts manage to offer useful information and advice without being absolutist about it, claiming superior authority, or slagging the dominant standards bodies. And making some mistakes, while inferring their infallability. Just sayin.

Hiding your qualifications is not humble. I absolutely do not claim that I don’t make mistakes and when pointed out, I always accept and learn from that.

I would counter your statement with how hard can it be to be respectful during discussions and not retort to personal insults? You seem to forget that I provide my expertise here free of charge for every reader to use. Or maybe that is what you don’t like, may be you charge for this service to your customers?

I call the diagram that I posted authoritative not because I made it but because it is the preferred setup worldwide. Even in the US where the big installers all say “yes, ABYC” and proceed to install Victron isolation transformers like in this diagram. And for good reason!

On bashing standards bodies… dominant? IEC is worldwide and dominant, NEC and ABYC are just national bodies. Not that I would not “slag” the IEC, they deserve their share too. You said so yourself before: they are political bureaucratic organizations, always too slow and sometimes ignorant of developments in the field that they are supposed to regulate. ABYC is different but has shown to be no better, if not worse.
I don’t have the answer for how to do this better, but anyone reading that draft Lithium TE-13 document knows it is a complete failure of expectations.

[goboatingnow]

I'd appreciate a cite for that, if possible, please.

From ISO 13297

3.8
isolation transformer
transformer installed in the shore power supply circuit on a craft to electrically isolate all the normally live conductors (3.11) and the protective conductor (3.10) on the craft from the AC system conductors of the shore power supply

[goboatingnow]

Originally Posted by Lake-Effect

Who could disagree that the ISO pedestal solution is far and away the best solution? But the problem exists in N America, NEC wasn't addressing it, and the ABYC would be wrong to ignore it.

We can agree to disagree here I dONT see ABYCs role to fix issues that should be addressed by the NEC.

The iso transformer reduces the opportunities for putting hot shorepower AC onto a boat's metal and hence into the water, but it does not completely eliminate that risk.
......

.

for all extents it does completely eliminate that risk. Once you have a discontinuous( isolated) ground , seawater simply cannot become a fault return except under bizarre conditions requiring multiple faults simultaneously

As I said a continuous ground degrades onboard safety not enhances it. It inserts metal surfaces in contact with seawater into the fault return , whereas before these where not in that circuit with an isolated ground.

ABYC has put a problem ( electro sea shock ) in front of on board safety and is attempting a fix what is rightly in the nec domain .ABYC has its priorities wrong and ISO hasn’t ( in this case )