I am confused as to what a galvanic isolation transformer (GIT) is and what/how it does.

Ours is an American boat - with 110V circuits and 'protected' by a galvanic isolation transformer.
The previous owner also installed a 240V Generator and added a few 240V circuits in Toodle-oo!

I am now plugged into 240V shore power and realize that I don't have a GIT specific to that circuit... - or do I? Since it operates on the earth, is the GIT working no matter what shore supply is applied? (I'm 98% sure that the earth of both circuits is connected!)

I have not noticed significant anode erosion in the past - I guess I'll find out how badly I screwed up in a couple of weeks when they haul the boat!

Bill Balme

Hi Bill,

I am no expert. My understanding:
Galvanic isolators (GIs) are not, to my knowledge, referred to as galvanic isolator transformers. They are not transformers: they just isolate. If I am correct in my former statement, I suspect you are conflating GIs with isolation transformers which are the gold standard in protecting the boat, but a whole separate order of size and complexity. It is possible that GIT may be a way of describing equipment on your side of the pond, but I have not heard it before.
A galvanic isolator (GI) is a fairly simple safety device (small in size and weight) that breaks the green ground wire of your shore power cord and the device is inserted in series. Its job is to block low voltage DC current (the kind that causes galvanic corrosion), but still allow AC current from a fault flow through thereby protecting the user from the kind of shock one might get say, from a defective toaster.

If you do have an isolation transformer (IT), unusual in cruising sailboats our size, but not unheard of (large box weighing 50-60 lbs, 20-30 kg and more complicated wiring), there are all sorts of possibilities: most are programable. Now I am operating above my pay scale, but ITs can be 1-1 (110 v to 110 v) or they can be 1-2 (110 transformed into 240 and vice versa 2-1). They also galvanically isolate, protect against some forms of shock, and ensure that the power on the boat is clean and pure and consistent even if the input power is not.
I do not believe that ITs change hertz, so one has that problem to deal with.
While on the subject, my understanding is that those of us with older boats might swap out our GIs and benefit from the advances made in design in recent years.

My best, Dick Stevenson, s/v Alchemy