Earth leakage?? and a tingle of metal socket face ??

[Titan]

hiya folks

For many months now been contentedly working on boat with running the inverter and working of an exstension lead, this week ive wired up the ring main through rcd and been using sockets, today got a kick of the metal socket face, checked all wiring connections, found to be good. When measured socket face to hull with a meter it read 100v a/c? after checking the net , i put in a earth from rcd to inverter chassis, i wrongly assumed that the earths in the supply from inverter to rcd would suffice, Since making this additional earth path all is well. My concern is now that this spurious leakage found at socket face is now a leakage through hull to water ?... and this raises concerns that if thats the case? whats stopping the hull to slowly dissolve ? ................... what am I missing or doing wrong... all advice appreciated regards martin

[Paul C]

What kind of inverter (please be as detailed as possible)? Specifically, is it neutral-earth bonded? Or some variation on this, which is less safe and some of the variations can't be integrated into an RCD (which requires N-E bonding to work properly). Somewhere on the forum is a post by Gibbo which explains the 3 variations on cheap inverters, how to test which one yours is, and how to wire them up safely (if its possible).

[Keeping Up]

The leakage is likely to be very small - a minute leakage will register on the meter and also will be detectable from touching a socket plate. The current from a disconnected earth can be felt clearly but is probably only one or two thousandths of an amp - milliamps, or mA - and it takes about 30mA to be at all dangerous.

 

It is important that your neutral and earth are bonded together and are connected to the boat's hull, correctly and in a manner which you understand rather than by chance. Basically the earth and neutral should connect to each other at the inverter output, and be connected to one point on the hull which is near to the point where the battery negative is connected to the hull.

 

The leakage however is entirely within your boat. Unless a shore line is involved, it will not flow through the hull to the water or the bank so it will not corrode the metal away. It is not good if it flows along the metal of the hull (which is why you need to understand your earth connections) but in fact as it's a.c. it would not cause significant corrosion even if it did.

[Skye]

It does sound like some floating earth type. akin to coupling the earth at the inverter to a centre tapped transformer, hence the half voltage on what should be a solid earth, the socket fronts.

 

To be honest I would suggest getting an electrician to your boat.

 

I live too far away but I'm sure there are some nearby.

 

David

[nicknorman]

Not only should the inverter neutral be connected to earth but also the earth line at the inverter / sockets must be connected to the hull at some point. if you think about it, if hull is connected to the socket face (via the earth connection) you can't get a tingle from it.

[Titan]

Thankyou all for your replys, since second earth has been in place all seems well, the inverter is a sterling. I called them today and they confirmed all should be well with the second earth from rcd to chassis. Once again a big thankyou regards martin