Galvanic isolators

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Fourbees

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Has anyone out there actually got a galvanic isolator on their boat? I have yet to meet someone who has, but the sellers of these gadgets claim that they are essential to prevent corrosion of anodes etc. when in a marina where people use shorepower. Do they actually work, in UK marinas? We get through anodes at a shocking rate - they last an even shorter time than politicians' promises!
 
Yes, upgraded the mains power circuit on our boat last winter.
Using the 'INSTALLING 240volt AC SHOREPOWER V4' article from the Moody Owners website to ensure the isolater was correctly connected.
Difficult to assess the performance until lift out this winter.
 
Mine definitely works - I think I was earthing the whole pontoon when I was at Emsworth.
 
I fitted one about three years ago, when I fitted a shore power system to our boat. I found a lot of ignorance about these, as a lot of people didn't know what they were for. Our anodes survive two or more years, generally, so I can only assume that the isolator is working.

The IEE Wiring Regulations are being updated in Jan 2008, with Marinas finally being covered by the regulations. The guidance notes produced by the IEE recommends that an isolating transformer be provided with the earth connections completely separate. No mention is made of galvanic isolators, but I'm following the posts in the IEE journals to see if any reference is made to these.

If you want any more info, pm me.
 
I don't know of any marinas that use isolating transformers. It will be a very costly job. I reckon you're better off with individual transformers ie your own because once you start earthing all the boats together you're back to square one.
 
[ QUOTE ]
The guidance notes produced by the IEE recommends that an isolating transformer be provided with the earth connections completely separate. No mention is made of galvanic isolators

[/ QUOTE ] With the ships "earth" not connected to the shore earth the need for a galvanic isolatator is eliminated, at least in theory. It is therefore not surprising that no mention is made of them. Where would you fit one? The very connection that they normally go in will cease to exist!
 
[ QUOTE ]
[ QUOTE ]
The guidance notes produced by the IEE recommends that an isolating transformer be provided with the earth connections completely separate. No mention is made of galvanic isolators

[/ QUOTE ] With the ships "earth" not connected to the shore earth the need for a galvanic isolatator is eliminated, at least in theory. It is therefore not surprising that no mention is made of them. Where would you fit one? The very connection that they normally go in will cease to exist!

[/ QUOTE ]

The IEE Wiring Regulations rarely offer one solution to a problem. If you look at the following site:

http://www2.theiet.org/Publish/WireRegs/...r_locations.pdf

You'll see they offer three solutions, however in the draft of the new regulations, figure 709.1 &2 shows a completely different set of connections, with no isolating transformer, but with the protective earth continuous from the boat to the marina supply.

As with previous editions of the wiring regulations, I'm expecting the IEE to issue updates and additional guidance sometime after the regulations are published, but in the meantime I'm sticking with a galvanic isolator.
 
Yes I fitted one, because everyone else around has - which means that in the event of a probem my boat will be earth for the pontoon - not a good plan. My anode lasted 2 seasons before (that is 50% gone before replacement) so I wait for the next liftout to see if its made a difference.
 
With an isolation transformer the marina earth should be connected to the frame of the transformer and the local earth connected to one side of the secondary of the transformer which meand as you say no direct connection between marine and boat earth there no galvanic isolator needed but all safe. only eatrs needed is a RCD in the transformer secondary on the outlet side of the earth neutral connection.
 
As Roger says the frame of an isolating transformer will be earthed to the shore earth. Only two conductors will come aboard from the transformer secondary winding and one of those will be grounded to the ships "earth" system to to form a neutral.

The transformer will protect you from obscure faults on the supply but on-board you will still need an 30mA RCD to give you the normal level of personal protection.
 
Not really happy with that IET info.

(PS for those that are not up to date with the Ts and Ss and Cs look at:
http://www.iee.org/Publish/WireRegs/Wiri...s_answered.pdf)

So look at Figure 1 on page 15. First they seem to have different boats for different marinas! Does that mean without an isolation transformer I can only go to certain marinas?

The third example is scary. I have no RCD on the boat but I always fit one on the shore end of the cable if the marina one does not exist.

In this case a double fault on the cable does not get protected. A double fault is where the cable has 2 exposed conductors over its length. On a pontoon this would allow a potential along the wet wood. i.e do not use long strides or you will feel a tingle!

Also assuming the third example, a single fault on the pontoon 3 core flexible cable, connecting the live to the water would not be protected. However the return path would be from the boat earth. Not safe for the divers!

Then there are the issues of isolating transformers. They are a terrible waste of energy. They use energy even when the boat is not using any. So for the sake of a bilge pump you burn 45W continuously. Which is 45 * 24 *365 = 394kW Hours


There is so much confusion here that Victron do not even recommend connecting the neutral to the earth on the secondary side! So how the RCD works is beyond me. They have different setup for in and out of the water!
http://www.victronenergy.com/upload/documents/Datasheet-UK-Isolationtransformer.pdf

However, Mastervolt do connect it.
http://www.mastervolt.com/com/53/product/5490/isolation_transformer_ivetd_35_kva16a_torroidal.html


My view is that they should go off and rethink that document and put the responsibility on the marina to supply a safe system.
1. They provide the RCD shore side ALWAYS
2. They provide the local water earth ALWAYS.

It is then up to the boat owner to add to the protection by providing an isolating transformer and additional RCD if they wish.


This does not recognise the fully isolated hull boats (of which most of the super yachts are) and their effects on the system.


The new regulations draft seem to miss out the third option but the first 2 options do not even state what the PE shore side needs to be connected to. Cleats? frame? Local water earth? Hose pipe stands?

Are they nuts! Thats what comes of having a sales man as the president. Knew him when others used to call him a used car salesman.
 
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