Electrical Grounding Bavaria 46 - 2008

[Bavaria 46]

A cable labeled “Masterdung“ is fixed to one of the keel bolts. I expected that the electrical grounding of the power outlets is connected somewhere with this cable. Following I expected an electrical resistance from close to 0 Ohm. I found 800 - 1000 kOhm. The same between battery minus and “master grounding“.
On the bolt of the Zinc anode the electrical resistance between ground of the power outlets and between battery minus is - as expected - 0 Ohm.
I am installing an isolating transformer.

The question is, if i can expext a sufficient grounding on the boat side of the insulating transformer in these conditions.

Any ideas about the high resistance between “master grounding“ and other ground contacts?
Best Regards
Ingo

[tiger79]

I believe that the "masterdung" cable is connected to the mast step, to act as grounding through the keel in the event of a lightning strike.  Therefore you won't find electrical continuity with other electrical ground circuits.

Which transformer are you fitting?  And why choose a transformer rather than a galvanic isolator?

[Bavaria 46]

Of course this cable should be connected to the mast / rigg. I will verify this next time, to be sure. My expactation was, that the rigg / mast and the "boat ground" should be electrically connected. But possibly you are right and there is no connection between mast & "boat ground". When the question would be, why the electrical resistinace ist no infinite high. (The boat is on shore in dry storage).

The transformer I am fitting is a Mastervolt GI 3.5.

I choose the transfromer, as from my knowledge a galvanic isolator in the ground cable is not compliant with German regulations (VDE).

[symphony2]

As said the cable from the mast to the keel is to ground a lightening strike. Does your boat have a saildrive or a shaft drive. If a saildrive it does not need any other anodes. If shaft drive  the hull anode could be bonded to the shaft via the gearbox (and a strap across the coupling if it is flexible) to protect the propeller. However many boats avoid this by using a shaft anode and possibly an anode on the propeller itself if a folding or feathering type. There is nothing else on the standard boat that needs an anode. I don't think the 240v system would have been grounded originally, but it is common now to ground it to water and many like Bavaria use an anode for this, but it is not connected to anything else. Not sure why you want to fit an isolating transformer. It is more common to fit a simple galvanic isolator between the shorepower input and the distribution panel.

I am surprised if a galvanic isolator does not comply with regulations. The regulations governing electrical systems on boats are in the RCD and as far as I am aware it allows galvanic isolators (although I have not checked) which are widely fitted.

[Bavaria 46]

The boat has a saildrive. The central hull anode has already been fittet on the boat as I bought it in 2017. Ground and DC minus is porperly connected to the hull anode.

Each season I have an issue with the adheasion of the coating of the saildrive & the stern thruster pods (independently if I do the coating myself or the boatyard).

The red LED in the 230 V panel, which is indicating a wrong polarity between phase (L) and neutral (N), is glowing in the home box. At any other port it is working fine. Therefor I believe that something is not well wired in the harbour or on one of boats in my vicinity. The isolating transformer should solve this issue

Galvanic isolator: I use Google  to try to figure out, if a galvanic Isolator is compliant with German regulations. Difficult, but I don't find what I  remember. It seems that since some years it is compliant under some circumstances, e. g. fail safe construction of the isolator.

[symphony2]

Is you saildrive isolated from the engine? Or is it the type that has return earth? With an isloated saildrive there is no need to ground the DC negative. I suspect somebody in the past has tried to cure a "problem without understanding what they are doing.

You say the coating on the saildrive housing is coming off - do you mean the antifoul you are applying or the original epoxy coating? If the later that suggests the ring anode is not working or something is connected to the saildrive that should not be.

Don't think it is anything to do with your 230v system. What you are seeing with the panel lights is the reverse polarity indicator working. It happens when connected to shorepower that is not wired the same L&N as your boat system because in Europe it varies from installation to installation whereas the boat is only wired one way.

Don't think you will find GIs covered by the VDE regulations as they are for domestic installations, not boats. There are various different types of GIs some are just basic others have failure indicators. They are perfectly safe to fit to your 230V system in the boat.

[Bavaria 46]

I think the saildrive is electrically connected to the engine. It could be that the ring anode is not working properly. The  anode is annually replaced by the boat yard. No idea why it should not work.

The reverse polarity light is working fine. If L and N is exchanged it is clear on. Having right polarity it is in all harbors completely dark. Exception: The home box. There it is clearly on if I exchange L and N, but not completely dark having L and N in the right polarity. It is glowing in that box with 20 % brightness.

Is there anything (despite the price) not to install an isolating transformer? The Mastervolt Mass Gi 3.5 is not really heavy. (6 kg)

[tiger79]

I think the saildrive is electrically connected to the engine.

It should be isolated.  There should be plastic insulators between the engine and saildrive, including on the fixing bolts.