Smart chargers and galvanic isolators

[VicS]

I said this way back in post #2 and again (in more detail) in post #11

So you agree with me ! That's good, not confusing.

 

[PaulRainbow]

So you agree with me ! That's good, not confusing.

As i said it first, it's good to see that you agree with me :encouragement:

 

[BabaYaga]

You misunderstand the purpose of the bonding circuit. It is not to connect anything to "ground". It is to protect persons not on the boat from electric shock in the event of a fault that allows the hull or a metal component on the vessel to "leak" 240v into the water. This would cause anyone in the water near the boat to receive an electric shock as the fault may not trip the RCD. If the shore power ground is bonded to the hull (metal boats) or the anode bonding circuit (non-conductive hulls) then any fault that could allow 240v into the water is guaranteed to trip the RCD.

Really? That’s interesting, please explain further: As a RCD trips as soon as there is current imbalance between line and neutral, how could current ”leak into the water” while preserving balance between L and N?

 

[PaulRainbow]

Really? That’s interesting, please explain further: As a RCD trips as soon as there is current imbalance between line and neutral, how could current ”leak into the water” while preserving balance between L and N?

Remind us why you think the shore power ground is connected to the hull or anode bonding circuit and what it achieves ?

 

[lw395]

Had a quick look at the Smartgauge website. It's a bit focussed on Narrowboats. Personally I think a steel hull needs something to ensure there's a limited potential difference between the guardrail on your left hand and the shore ladder on your right as you board or alight. That something is usually a GI.
...

How does that work ?

A 'galvanic Isolatior' is what would be called a 'diode clamp' elsewhere in electronics.
It's function is to allow the two potentials (yacht 'ground' and shore power 'earth') to be different up until the point that a few diodes in series start to conduct. There are diodes in both directions, so as soon as the two 'earths' 'grounds' or whatever were calling the green/yellow wires are different by more than the 'Vf' of the diodes, enough current will flow to keep the voltage difference small.
So in a fault situation, the diodes will drop a couple of volts, the resistance of the diodes is low enough that the fuse will blow or the shoreside RCD will pop, depending on the nature of the fault.

The hope is that the natural difference between the ground potentials in normal operation is low enough that the diodes don't conduct, so in normal operation, it looks enough like an open circuit that the shore power earth isn't putting current through your anodes.

 

[BabaYaga]

Remind us why you think the shore power ground is connected to the hull or anode bonding circuit and what it achieves ?

The 'anode bonding circuit' appears to be your own addition to this issue. Neither ISO 13297 nor ISO 10133 makes any reference to anodes as far as I can see.

Three important points from the relevant ISOs upon which I base my thinking:

The ISO 13297 requires the AC protective conductor to be connected to the hull (if this is metallic) or, for a non conducting hull, to "the main grounding/earthing point of the craft".

The above mentioned point is, according to ISO 10133, a point or bus that provides connection to the common ground for the DC negative conductor and for the AC protective conductor. It is noted that this point may include any conductive of the wetted surface of the hull in permanent contact with the water.

For crafts with a fully insulated DC system (refer to ISO 10133 for definition), the AC protective conductor shall be connected to the hull (if metallic ) or else to the craft's external ground/earth or ground plate.

This is what leads me to the conclusion that the over all objective of the bonding of AC PE required by the ISO is to establish a path to ground, which on a vessel is the surrounding water.
As you probably know, if you have read the ISO's, they set the requirements but they do not give reasons or motives. So this is for the reader to figure out.
In my interpretation the purpose is to establish a secondary, alternative path to ground (the sea) for the PE, which will function if the primary path, the shore cable PE connector, should fail.
Nothing in the ISOs that I have read suggests that the explanation you gave in post #18, about protecting swimmers from electric shock, should be a better guess.

 

[PaulRainbow]

The 'anode bonding circuit' appears to be your own addition to this issue. Neither ISO 13297 nor ISO 10133 makes any reference to anodes as far as I can see.

Your understanding of the subject is exceedingly poor.

The point of bonding AC earth is to bond it to whatever metal equipment is in the water. In the case of steel/alloy boats it's the hull. In the case of non-metallic hulls it's to whatever metal parts of the boat is in the water, that can conduct AC current into said water. Various editions of the ISO have specified various locations, but they all end in the same result, the anode bonding circuit is connected to AC ground.

Three important points from the relevant ISOs upon which I base my thinking:

<snip>

This is what leads me to the conclusion that the over all objective of the bonding of AC PE required by the ISO is to establish a path to ground, which on a vessel is the surrounding water.

So you think that it's to connect the ground wire (this is connected to ground at the shore) to be connected to the sea ? The path to ground for the AC circuits already exists.

In my interpretation the purpose is to establish a secondary, alternative path to ground (the sea) for the PE, which will function if the primary path, the shore cable PE connector, should fail.

Brilliant thinking, if there is a problem, dump the AC current in the sea !

Nothing in the ISOs that I have read suggests that the explanation you gave in post #18, about protecting swimmers from electric shock, should be a better guess.

It's not a guess, it's a fact. It takes a lot less current to paralyse a swimmer than it does to trip a 30ma RCD.

The effects of stray current are even worse in fresh water.

You once again misunderstand how things work and apply your own twisted logic, you then compound your errors by refusing to even consider that you may be mistaken.

If you don't beleive it's anything to do with protecting swimmers, you might want to have a word with the parents of these kids : https://grandhaven.s3.amazonaws.com/pdf_documents/marina/esd_brochure.pdf

Please learn something before replying.

 

[lw395]

......
The ISO 13297 requires the AC protective conductor to be connected to the hull (if this is metallic) or, for a non conducting hull, to "the main grounding/earthing point of the craft".

The above mentioned point is, according to ISO 10133, a point or bus that provides connection to the common ground for the DC negative conductor and for the AC protective conductor. It is noted that this point may include any conductive of the wetted surface of the hull in permanent contact with the water.

For crafts with a fully insulated DC system (refer to ISO 10133 for definition), the AC protective conductor shall be connected to the hull (if metallic ) or else to the craft's external ground/earth or ground plate.

This is what leads me to the conclusion that the over all objective of the bonding of AC PE required by the ISO is to establish a path to ground, which on a vessel is the surrounding water.
As you probably know, if you have read the ISO's, they set the requirements but they do not give reasons or motives. So this is for the reader to figure out.
In my interpretation the purpose is to establish a secondary, alternative path to ground (the sea) for the PE, which will function if the primary path, the shore cable PE connector, should fail.
Nothing in the ISOs that I have read suggests that the explanation you gave in post #18, about protecting swimmers from electric shock, should be a better guess.

No, the wiring standards are not there for technicians and fitters to figure out 'why?', the standards are there for installers to do as they're bloody well told.

The function of a protective earth is to connect all exposed metal parts with a low resistance. So that in a fault condition, you cannot have a dangerous voltage between two conductive things you might touch.
The sea is not very relevant as it's not really in circuit in a plastic boat. It is a bad idea to return any currents to the hull or sea, as it results in dead fish/swimmers and the hull or thru-hulls dissolving.
The hull must be a single node in the electrical circuit.
So there is no circuit loop electrical equipment>hull>sea>(another point on the hull>electrical system
Protective Earth is a separate function from anode bonding.
Both should be separate from any current-carrying return.

When shorepower is plugged into the boat, the incoming 'shore earth' is a different potential from the sea or the ship's PE. That is the point of GIs and isolating transformers.

 

[webcraft]

When shorepower is plugged into the boat, the incoming 'shore earth' is a different potential from the sea or the ship's PE. That is the point of GIs and isolating transformers.

But . . . if the shorepower earth is not connected to anything on the boat except shorepower operated equipment, is there an issue?

And is this perhaps more important if you have 12V/240V switchable equipment (eg fridge) ?


- W

 

[lw395]

But . . . if the shorepower earth is not connected to anything on the boat except shorepower operated equipment, is there an issue?

And is this perhaps more important if you have 12V/240V switchable equipment (eg fridge) ?


- W

If you touch something earthed to shore power at the same time as something earthed to the boat's metalwork, you may find it an issue.
It depends on what fault conditions you envisage.

Life gets more difficult if you start contemplating inverters or generators on the boat.

 

[Heckler]

.
I am in n the process of fitting a rudimentary shorepower system (consumer unit plus sockets) to the new boat. The system includes a CTEKM200 charger.

I am fairly convinced that a galvanic isolator would be an affordable and sensible precaution, as the boat will be left unattended plugged into shorepower for extensive periods. However, I read somewhere that GIs may not work with devices with switch-mode power supplies. Which the charger probably has?

All Greek to me - any thoughts?

- W

Dont leave connected to shore power when away. Simple, in all the years we have been away we have never left it connected. We leave the solar on and that keeps the batteries up to scratch. When we only had 56 watsts we didnt even use a controller, it wasnt a problem with 440 amp hrs hose capacity.

 

[PaulRainbow]

But . . . if the shorepower earth is not connected to anything on the boat except shorepower operated equipment, is there an issue?

There are millions and millions of boats wired exactly like this. But, it depends what you mean by "issue". If you mean galvanic corrosion, then i answered that way back in post #2

If you mean "what could possibly go wrong and give someone an electric shock", that's a different story. If you managed to touch something live and touched something connected to the anode bonding circuit, then you could find yourself with an issue. It could also be possible to leak enough AC current into the water to kill a swimmer, as already discussed. All of this would require some very unlikely fault scenarios to happen though.

And is this perhaps more important if you have 12V/240V switchable equipment (eg fridge) ?

Can't see a relevance there.

 

[lw395]

Dont leave connected to shore power when away. Simple, in all the years we have been away we have never left it connected. We leave the solar on and that keeps the batteries up to scratch. When we only had 56 watsts we didnt even use a controller, it wasnt a problem with 440 amp hrs hose capacity.

Did you not have a spot of bother with you house bank early this year?

 

[Heckler]

Did you not have a spot of bother with you house bank early this year?

Yes, after 9 years they gave up the ghost! Not bad eh?

 

[lw395]

Yes, after 9 years they gave up the ghost! Not bad eh?

Sounded fairly bad at the time, I'd prefer my batteries to die gracefully without the drama TBH.

 

[BabaYaga]

Various editions of the ISO have specified various locations, but they all end in the same result, the anode bonding circuit is connected to AC ground.

This makes no sense at all to me. Where do you see references to anodes? Have you actually read the ISO 13297?
Many GRP boats have no anodes at all or only anodes attached directly to the items they are protecting, like a shaft or prop anode. I cannot see in what way anode bonding relates to this issue.

So you think that it's to connect the ground wire (this is connected to ground at the shore) to be connected to the sea ?

I certainly do.
Why else would there be a requirement in the ISO to connect the AC protective connector to the hull (metal boat) or else to "the main grounding/earthing point of the craft"?
And further more, in the case where the DC negative cannot be used for groundning/earthing purpose (because the DC system is fully insulated), to an external ground plate?

The path to ground for the AC circuits already exists.

Yes, as long as it is not broken.
As VicS mentioned in post #5, a previous edition of the ISO allowed for relying only on the shore cable protective conductor, provided there was a RCD onboard protecting the vessel.
In the later editions this is no longer considered safe. Which is why the requirement now is to connect the protective conductor from exposed conductive parts of electrical equipment etc to the crafts own ground as well as to the grounding conductor through the shore cable.

Brilliant thinking, if there is a problem, dump the AC current in the sea !

You seem to believe the sea cannot be used for protective grounding/earthing? Why do you think the ISO requires the installation of an external ground plate in certain circumstances (see above)?
And in the case where an isolation transformer is installed, where do you think AC is dumped if there is 'a problem'?

You once again misunderstand how things work and apply your own twisted logic, you then compound your errors by refusing to even consider that you may be mistaken.

If you don't beleive it's anything to do with protecting swimmers, you might want to have a word with the parents of these kids : https://grandhaven.s3.amazonaws.com/pdf_documents/marina/esd_brochure.pdf

Please learn something before replying.

Electric shock drowning (ESD) is indeed a serious matter, but bringing those tragic events into this discussion is totally off the mark.
Why? Because these accidents occur when AC leaks into the (mostly fresh) water and there is no RCD onboard to interrupt it!
But a RCD is a requirement set by the ISO that we are discussing. The installation of a RCD (or Equipment Leakage Circuit Interrupter in Amercan) is also the recommended measure to eliminate this hazard.
Please read and maybe you will learn something:
https://www.boatus.com/seaworthy/magazine/2013/july/electric-shock-drowning-explained.asp

If you reply to this post, please try to be civilized and focus on the subject. Remarks like 'exceeding poor understanding' and 'twisted logic' add no weight to your arguments, quite the opposite really.

 

[PaulRainbow]

If you reply to this post, please try to be civilized and focus on the subject. Remarks like 'exceeding poor understanding' and 'twisted logic' add no weight to your arguments, quite the opposite really.

As usual, you apply your own strange logic and ignore everything that is said by anyone else. So there really is no point in replying.

 

[VicS]

This makes no sense at all to me. Where do you see references to anodes? Have you actually read the ISO 13297?
Many GRP boats have no anodes at all or only anodes attached directly to the items they are protecting, like a shaft or prop anode. I cannot see in what way anode bonding relates to this issue.



I certainly do.
Why else would there be a requirement in the ISO to connect the AC protective connector to the hull (metal boat) or else to "the main grounding/earthing point of the craft"?
And further more, in the case where the DC negative cannot be used for groundning/earthing purpose (because the DC system is fully insulated), to an external ground plate?



Yes, as long as it is not broken.
As VicS mentioned in post #5, a previous edition of the ISO allowed for relying only on the shore cable protective conductor, provided there was a RCD onboard protecting the vessel.
In the later editions this is no longer considered safe. Which is why the requirement now is to connect the protective conductor from exposed conductive parts of electrical equipment etc to the crafts own ground as well as to the grounding conductor through the shore cable.




You seem to believe the sea cannot be used for protective grounding/earthing? Why do you think the ISO requires the installation of an external ground plate in certain circumstances (see above)?
And in the case where an isolation transformer is installed, where do you think AC is dumped if there is 'a problem'?




Electric shock drowning (ESD) is indeed a serious matter, but bringing those tragic events into this discussion is totally off the mark.
Why? Because these accidents occur when AC leaks into the (mostly fresh) water and there is no RCD onboard to interrupt it!
But a RCD is a requirement set by the ISO that we are discussing. The installation of a RCD (or Equipment Leakage Circuit Interrupter in Amercan) is also the recommended measure to eliminate this hazard.
Please read and maybe you will learn something:
https://www.boatus.com/seaworthy/magazine/2013/july/electric-shock-drowning-explained.asp

If you reply to this post, please try to be civilized and focus on the subject. Remarks like 'exceeding poor understanding' and 'twisted logic' add no weight to your arguments, quite the opposite really.

But the RCD trips at 30mA. Much lower currents are dangerous to swimmers so the on board RCD does not necessarily protect them. I belive this has been mentioned recently in a similar thread if not earlier in this one.

 

[BabaYaga]

But the RCD trips at 30mA. Much lower currents are dangerous to swimmers so the on board RCD does not necessarily protect them. I belive this has been mentioned recently in a similar thread if not earlier in this one.

This is a valid point, but one has to consider the difference in current level and effect on the human body depending on whether a person is actually touching the conductive part or merely in contact with it through the water.
Even in fresh water there will be some dissipation of the current, though much less than in sea water.
I do agree for instance that it could be dangerous for a diver to touch the propeller of a boat connected to shore power even if there was a functioning RCD onboard.

It might be of interest to some, that the Swedish Cruising Association, in cooperation with the relevant authorities, already about 10 years ago published a method for boat owners to be able to comply with the ISO 13297 and still avoid the potential corrosion issues without having to install an isolation transformer or a galvanic isolator (which works poorly in many Nordic settings due to the low conductivity of the bedrock).
The method involves installing an external copper grounding plate, which establishes this good, low resistance path to ground which I mentioned in my first post to this thread. But the recommendation in this case was to choose a RCD with a tripping value of 10 mA.

 

[SlowlyButSurely]

It might be of interest to some, that the Swedish Cruising Association, in cooperation with the relevant authorities, already about 10 years ago published a method for boat owners to be able to comply with the ISO 13297 and still avoid the potential corrosion issues without having to install an isolation transformer or a galvanic isolator (which works poorly in many Nordic settings due to the low conductivity of the bedrock).
The method involves installing an external copper grounding plate, which establishes this good, low resistance path to ground which I mentioned in my first post to this thread. But the recommendation in this case was to choose a RCD with a tripping value of 10 mA.

I don't understand how this could work. Could you please provide a link to an explanation?