Galvanic isolator- is it connected correctly

[Daydream believer]

The common connection of a GI is in series with the mains earth line coming in. However there seems to be an alternative arrangement where the collected earth lines of the mains equipment is connected to the sea via a GI. Hence possibly explaining the GI connection to the engine. That might be ok if all metal parts in contact with water are also connected to engine earth. I doubt your wear on anodes has been caused by mains connection if you are not connected 24/7. ol'will

That is not exactly correct. The GI is connected to the saildrive. The saildrive is isolated from the engine so as the earth wire from the GI is to the saildrive only, then it does not connect to the 12 V system of the engine.

 

[PaulRainbow]

The common connection of a GI is in series with the mains earth line coming in. However there seems to be an alternative arrangement where the collected earth lines of the mains equipment is connected to the sea via a GI. Hence possibly explaining the GI connection to the engine. That might be ok if all metal parts in contact with water are also connected to engine earth. I doubt your wear on anodes has been caused by mains connection if you are not connected 24/7. ol'will

This is wrong !!

There is only one correct way to connect a GI, incoming shore power to one terminal of the GI, the other terminal connects to the boats PE circuit.

 

[Daydream believer]

This is wrong !!

There is only one correct way to connect a GI, incoming shore power to one terminal of the GI, the other terminal connects to the boats PE circuit.

PE... ?

 

[PaulRainbow]

PE... ?

Protective Earth.

If you remove the connection to the saildrive yours will be correct. Just double check that if the connections are marked "supply" and "boat circuits" (or similar) that it's correctly connected. Some can be connected either way and won't likely be marked.

 

[rogerthebodger]

This is wrong !!

There is only one correct way to connect a GI, incoming shore power to one terminal of the GI, the other terminal connects to the boats PE circuit.

Should the PE be connected to a hull earthing point on the boat side of the GI
Is that what the dice anode is for

 

[PaulRainbow]

Should the PE be connected to a hull earthing point on the boat side of the GI
Is that what the dice anode is for

Current new build requirements are, that there is a connection between the boats PE circuit and the water, various ways to achieve this, depending on the boats construction. Could be the hull of a metal boat, an existing hull mounted anode, a ground plane or a small button anode etc.

Older boats would not have necessarily been built with this connection, so don't need or benefit from, a GI. But if the connection is made, a GI should be fitted. As far as the GI is concerned, to connects between the incoming shore power and the boats PE circuit, typically the busbar in the consumer unit (but can go elsewhere).

An isolation transformer can also be used, in place of a GI, but that's a different subject.

 

[rogerthebodger]

Paul Thanks for your reply

I am not being provocative I just wish to clarify different approaches

The function of a GI is to block any DC Voltage UP to 1.4 ish volts which would stop and Galvanic current flowing between any dissimilar metals like a zinc anode and steel structure of the marina.

Must it be inline with the incoming PE or can it be just be between the PE and the water connection providing all the mains appliances and consumer unit are isolated from the water connection as on a GRP boat without any other PE connection to underwater fittings

I did it this way on my boat and my anodes have lasted many years

Even my prop-shaft and stainless steel prop are electrical insulated from the hull and engine

 

[Boater Sam]

Many GIs are now designed to block up to 2v DC to cope with all the horrible switch mode power supplies in modern appliances which have to have capacitor pi suppressors to stop the interference.

 

[Daydream believer]

I have now exposed & checked the wiring on my GI. It does sit in the earth line before the 240V shore power consumer unit. It has shore & boat connections clearly marked. I have actually found the instructions after 20 years. They make no mention of additional wires to a hull anode.

I have an additional wire from the "boat" terminal that goes to the saildrive; or did, but now disconnected.
Presumably this is the wire that needs to go to a hull anode, as suggested above. I will deal with that when laid up at the end of the season.
Thanks one & all for the comments thus far