Isolating Transformers, The Earth wire connection conundrum

[transmitterdan]

Originally Posted by chala

It is rare to see a boat connected to shore power with its anchor deployed.

It's not rare in the Mediterranean and probably many places where there isn't room to side tie.

[s/v Jedi]

Originally Posted by chala

I agree and I would ad: transformer to the list. (This ground protects against failures of the shorepower cord or inlet,) and transformer. Fine Not recommended will defeat the purpose of having an Isolation Transformer. The above is more about galvanic corrosion and as little to do with a correctly wired Isolation Transformer. It is rare to see a boat connected to shore power with its anchor deployed. I have a metal boat in which it would be very difficult to effectively isolate the chain from the metal hull. In the many years that I have been sailing this and a previous metal boat, I never had problem as described above.

It's apparently hard to understand, so let me try again: anchor is buried in the seabed, which is ground, connects to chain which connects to windlass. Now, if windlass is bonded, it connects to a bronze plate which is submerged in the water which is ground. This is the circuit and shore power is not needed for it.

Key to understanding this problem, is that the potential of ground in the seabed is different than the potential of ground at the bronze plate. This is why a current flows and chain is eaten away.

I know it has nothing to do with an IT. Who cares, better remember and make sure it doesn't happen to you too! I have seen two boats with the problem; one had a brand new 12mm stainless steel chain that lost 8mm in 3 weeks!