Galvanic Isolator Does it show shore power problems?

[Petronella]

Petronella is an old steel boat currently in a cradle in Grenada connected to shore power by a weatherproof pedestal into which we plug a standard 13 amp plug! We've been here about a week with no previous issues.

Today it rained hard and the AC leakage light on our galvanic isolator came on. My hunch is that this is a boatyard supply issue but I thought the galvanic isolator only showed 'boat' problems not 'shore' problems. Am I wrong?

 

[yachtorion]

As I understand it.. If the light is on then you have AC leaking to earth on the boat. The light is there to show you that the isolator has switched into non-isolating mode because it thinks there is a *potentially* dangerous fault with a voltage difference between earth ashore and earth on your boat above that you would expect from galvanic corrosion.

Perhaps some rain water got where it shouldn't? Do you have an RCD? If you have multiple breakers... does the light go off if you turn a particular one of them off?

Some have two lights or multiple lights with different meanings, but from your description I'm assuming this light is labelled AC leakage or you know it from the manual.

 

[Lon nan Gruagach]

Try switching off the shore power at the 13A plug, but leave it plugged in.
If the light stays on then the pedestal has a dodgy earth.
If the light goes off you have wiring problem.

I think...

 

[Petronella]

Thanks for replies.

Yachtailsa: We do have an RCD with three breakers. With RCD off the light was still on. I have two lights and the manual says the illuminated one was the AC leakage indicator.

It is possible rainwater got where it shouldn't have but I do think this is unlikely (I hope) as P is a very dry boat.

Dougal Tolan: That sounds a nice easy way to check. However the light has now gone out again! I'll have to wait for the next rainstorm and if it happens again I will report back.

Thanks.

Oh by the way. We also have, completely separately, one of those plugs you can plug into a socket to check the mains supply. This gave the standard OK result of 3 lights.

 

[VicS]

I'll have to wait for the next rainstorm and if it happens again I will report back.

Could rain have got into the shorepower in-take socket?

Maybe worth a few tests with a hose to spray water on parts of the shore power installation that could have been rained on