PaulRainbow
Well-Known Member
It won't work, the whole post is just more nonsense.
How can a metal plate negate the need for a GI ? A steel/ally hull has a fairly large metal plate in the water, it's called a "hull" lol
Smart chargers and galvanic isolators
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It won't work, the whole post is just more nonsense.
How can a metal plate negate the need for a GI ? A steel/ally hull has a fairly large metal plate in the water, it's called a "hull" lol
SlowlyButSurely
Well-Known Member
Thanks Paul. That's what I thought.
PaulRainbow
Well-Known Member
This is so ridiculous it has to be a troll
Installations either conform the the regs or they don't. What the hell do you think the conductivity of bedrock has to do with the functioning of a GI or isolation transformer ? The answer is, nothing. Both devices won't give a toss about Nordic bedrock.
That's just more nonsense. What difference is a metal plate on the outside of the hull going to make to anything ? It won't make a difference to the need for a GI. It won't make a difference to the need to bond the AC ground cable. If it did, there would be no need for either on a steel hull.
You claim that ESD has no place in this thread, then post a link to a page about it. The point of the regs that require the ISO to be followed are there to protect people, both on and off the boat. The various standards require that measures are taken to prevent AC current leaking into the water. Your interpretation is that the ISO is designed to dump stray AC current into the water by bonding the PE circuit to a metal hull or to external metalwork on GRP/wood vessels.
Do you not think those two things are at odds with one another ?
The point of AC bonding is to make anything and everything that can cause electric shock, both on and off the vessel, to be directly connected to the PE circuits, ensuring that stray AC currents cannot be carried through the water.
BabaYaga
Well-Known Member
Please follow this link:
https://www.batliv.se/wp-content/uploads/2015/11/LandstromRev3.pdf
The text is in Swedish (possibly you can try and run it through Google Translate or similar), but there are also four schematics. The first of these covers the situation that we are debating here, that is single phase shore power and no isolation transformer (or GI).
Jordfelsbrytare (JFB) is RCD in Swedish. Fritidsbåt = pleasure craft. In the lower left corner of the blue box representing the pleasure craft there is a metal link that is detachable. The purpose of this is that the PE onboard the craft shall be connected to incoming cable's PE when the boat is on hard standing and 'shore power' is used. (Hard standing = no water = no ground by way of the external plate, therefor the shore cable's PE wire is the only connection to ground and this must be used).
The text under the same blue box says that the external grounding/earthing plate that constitutes the 'boat ground' shall be at least 20 centimetres square.
I hope this will clarify.
BabaYaga
Well-Known Member
This is so ridiculous it has to be a troll
I'm no troll
I have contributed to these fora since 2008 and made well over 1 000 entries on various subjects. Anyone can check my record.
In this matter we are simply in deep disagreement, that's all.
Please see the link and explanation in post #44.
PaulRainbow
Well-Known Member
I'm no troll
I have contributed to these fora since 2008 and made well over 1 000 entries on various subjects. Anyone can check my record.
In this matter we are simply in deep disagreement, that's all.
Please see the link and explanation in post #44.
So, the way to stop galvanic corrosion, without fitting a GI, is to disconnect the shore power ground when the boat is in the water, what a great idea.
Among the many reason why this is a totally nuts idea is the fact that if this copper plate on the outside of the hull can conduct to ground, the boat is till connected to surrounding vessels etc.
It gets dafter by the day.
lw395
Well-Known Member
I take that to mean the link is disconnected when the boat is in the water:
Easily visible
switchover, must
be aware of
the boat is
dry with
shore
So there should never be a circuit Shore earth> boat wiring PE > ground plate > sea > shore earth.
No argument with bonding the boat to shore earth when it's ashore in the yard.
I've had that tingly feeling as you touch the ladder and the guardwires at the same time, it's something I can live without.
The Baltic is a lot less saline than the English Channel.
lw395
Well-Known Member
Sounds perfectly correct to me.
Basically, you have to trust that one of the two RCDs will work.
The function of the yacht's PE is to bind all the relevant exposed metal bits to the same potential.
The copper plate is there to ensure that if that potential is dangerously away from Land Earth, enough current must flow to pop the RCD.
If the boat had no metal in the water at all, then some dangerous faults would not pop the RCDs unless you bring shore earth into the boat.
BabaYaga
Well-Known Member
I would put that: 'Easily visible metal connection link, must be attached if the boat is on the hard with shore power'.
With this recommended setup the shore cable PE is taken onboard, but not connected to anything as long as the boat is in the water. This breaks the circuit between 'shore earth' and 'boat earth' (the sea). It is when these two 'earths' are at slightly different potential that corrosion problems are created.
True. That makes the hazard of ESD more pronounced here, so this is not something taken lightly upon.
SlowlyButSurely
Well-Known Member
Thanks Baba. Now I understand. This is a sort of bodge solution that relies on the copper ground plate passing enough current into the sea to trip the rcd. What about fresh water? This is not a proper solution at all and I don't think it would comply with the recreational craft directive
rogerthebodger
Well-Known Member
I can't see that either as I have a steel hull but need a GI to reduce erosion due to galvanic currents between mt anodes and externat metals (the aluminum boat next door)
In theory that is true but my steel hull is painted to prevent corrosion but has anodes welded to the hull that are not painted.
The paint is non conductive so can prevent current flow unless there is damage to the paint thus exposing the steel hull to be in direct contact with the water. This is when the anodes come into play and prevent the exposed steel from corroding away.
I know this as over the last 8 years my hull anodes have eroded away very little until last year with the damage to the paint film when out marina broke up and several GRP boats sunk. This year I pulled my boat out and the exposed steel was still bright but some of my hull anodes had eroded more than over the previous 8 years.
In my case the exposed anodes do provide a guaranteed current path to the sea water thus providing a secondary leakage current path and tripping my RCD. The GI stopes low voltage DC current flowing further protection the anodes from stray galvanic currents but allowing AC leakage current to flow back to the neutral earth connection at the sub station distribution mains transformer .
The ISO says that a PE to DC negative is not needed with and isolated DC system. When would a DC system on a GRP boat not be an isolated return if the engine was isolated from the prop shaft with a flexible coupling.
PaulRainbow
Well-Known Member
It says
ISO 10133 states
Those are from the 2000 editions of the ISOs, i understand the wording has changed somewhat in later editions. It's my belief that the original wording was based on the 12c negative being connected to the anode bonding circuit, hence to whatever metal parts where in the water, connected such that they could cause electric shock. I suspect that the wording evolved to try and cover those installations where this was not the case.
lw395
Well-Known Member
Is it really any worse than the earth wire of a house being connected to a metal rod hammered into the dry ground?
PaulRainbow
Well-Known Member
Is it as good as being connected to the correct shore power earth ?
Will it comply with the regulations ?
If something goes wrong and someone dies, will the installer of this installation be facing criminal charges ?
lw395
Well-Known Member
Maybe it's better than having your boat sink mid ocean because the skin fittings have been rotted by electrolysis?
Regulations are great when they're protecting you from what the committee had in mind when they wrote the regs.
One of my many workplaces was a high voltage lab, where every piece of mains powered equipment had the earth disconnected.
It seems to me that a GI is a reasonable compromise, provided you don't have enough 'earth' disparity to make significant current flow. An isolating transformer is the next step.
Bear in mind that proper ships work on completely different principles.
If you stuff your fingers in the 'mains' of a decent warship, the breakers won't pop, because it's better to lose the odd matelot than turn off the control systems and lose the whole boat.
matthewriches
Well-Known Member
Same on the 30kV output on some of the container ships. A person would vaporise with just a pile of teeth left before the circuit breakers would blow 
I remember my first day on an MSC when I was given a 10ft orange pole to pull some fuses Asshole slightly tighter than before, Sir. lol.
In all seriousness, thread spiralled out of control
Sort your DC Neg+E strap, fit a GI, ensure your mains install is protected with a suitable device and if needed get the system commissioned by a qualified professional that knows boats so you can sleep easy at night.
I remember my first day on an MSC when I was given a 10ft orange pole to pull some fuses Asshole slightly tighter than before, Sir. lol.In all seriousness, thread spiralled out of control
Sort your DC Neg+E strap, fit a GI, ensure your mains install is protected with a suitable device and if needed get the system commissioned by a qualified professional that knows boats so you can sleep easy at night.
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rogerthebodger
Well-Known Member
Yes I understand that as at one time it was considered that all underwater metal fittings must be connected (bonded) together and to the anodes. GRP boats mainly.
Now the view is that this not required as on a GRP boat the metal fittings would be insulated from each other by the hull. Metal boats like mine as quite different.
I agree with ISO 10133 that a fully insulated 2 wire system would have the dc netavive isolated from the ground (earth).
My main question is in practice when would that not be the case requiring the dc negative to be connected to the ground (earth) for GRP boats.
Now the view is that this not required as on a GRP boat the metal fittings would be insulated from each other by the hull. Metal boats like mine as quite different.
I agree with ISO 10133 that a fully insulated 2 wire system would have the dc netavive isolated from the ground (earth).
My main question is in practice when would that not be the case requiring the dc negative to be connected to the ground (earth) for GRP boats.