Galvanic Isolator while boat is ashore

[VicS]

OK found the original thread and see its a galvanic isolator

A question for VicS Have you any information on Figure 2 on the original thread. I thought galvanic isolators were connect in series as fig 1

They are my diagrams ........ I drew them to ask whether or not the arrangement in fig 2 was not acceptable.
IIRC my thinking was that any live to earth fault on the AC system should not result in a high current through the GI with a risk of damaging its diodes.
The question went pretty much unanswered as far as I remember, although eventually someone suggested that my thinking was not entirely relevant to metall hulled boats where a live to hull fault could well occur.

 

[rogerthebodger]

Vic

When you first posted the above diagrams I had a think about your Fig 2 arrangement in the context of my steel boat but I don't think I replied.

I do think it would perform the required function of protecting the anodes and as you say would also eliminate the GI carrying current in the case of live to appliance earth fault.

As has been discussed before in the case of a GRP boat I question the need to connect mains earth to any non mains equipment and only metal cased mains driven items need an earth connection, which would happen as normal in any metal cased mains appliance.

Like the interconnection of anodes to other wise insulated external metal fittings IMHO only causes the anodes to erode thus increasing the sales of anodes, like wise the connection of the mains earth to otherwise insulated external metal fittings on a GRP boat would require a GI to be fitted to reduce anode wastage. If the interconnection was not done a GI would not be necessary.

I repeat my above comment only applies to GRP boats, metal boats where all metal fittings and appliances would naturally be interconnected mains earth and GI would be necessary.

On my boat I do have a GI and currently it connected as Fig 1 but I will be changing to Fig 2 when I have time but as I do not have a shore power connection all the time IMHO the change is not urgent especially as in the last 3 years my anodes have only shown minimum erosion and no damage to my underwater paint job.

 

[Gumpy]

Fig 2 is ok on a steel boat provided you can guarantee that there are no ground to hull shorts anywhere on the boat which to be honest is unlikely on an older boat.

 

[mjf107]

Mains AC on boats

They are my diagrams ........ I drew them to ask whether or not the arrangement in fig 2 was not acceptable.
IIRC my thinking was that any live to earth fault on the AC system should not result in a high current through the GI with a risk of damaging its diodes.
The question went pretty much unanswered as far as I remember, although eventually someone suggested that my thinking was not entirely relevant to metall hulled boats where a live to hull fault could well occur.

Thanks for the reply, good Lateral thinking! It looks safer to me on a GRP boat if you must bond? But I'm no expert, it will be interesting to see what the new standard comes up with.

I,m with "Gibo" of Smart Gauge, the only "reasonably safe" system is an isolating transformer for complex electrical systems and essential with a metal hull no matter how complex. If anyone has doubts look at the number of faults illustrated on the Tony Brooks training site and the likely out comes.