Bav 33C - 2006 . Earth between DC and AC

[CRYSTAL]

Hi guys

I noticed that my dc earth and ac earth are not connected like my friends Bav42 which also has a hull anode.

Would it be recommended to do the same on mine? And at which point should I connect the two earths plus connection to the anode

ATB

[Kaptajnen]

Be very careful before making such a connection. Depending on how your engine's electrical connection is setup, you may inadvertently create a galvanic stray current when you are hooked up to shore power. In a worst case scenario, if your Bavaria is equipped with a 120S Volvo Saildrive, the aluminum housing of the saildrive becomes an anode and corrodes in a matter of hours.

[Symphony]

No need to connect them and definitely don't connect to an anode. It is not needed as the saildrive has its own anode and there is nothing else that needs an anode.

[CRYSTAL]

Cheers but to clarify a bit further it's SD130 and electricity isolated from the engine and verified with an ohm meter (thankfully).

Any ideas why I would measure 500mv between dc ac earth?

Every DC earth leads back to engine. AC earth is isolated.

Only unknown is the shore power where the 2 meet but don't touch. So when referencing with bav42, dc and ac earth are connected and then onto a hull anode. Hence my original query.

Tnx

[Kaptajnen]

Does your friend's Bav 42 also have a 130 Sail Drive?

[CRYSTAL]

Yep.

Mine is Oct 2006 and was lucky do get fitted with new model VP D1-30 / SD130.

Seems that all newer (post 2007) models have the hull anode.

Cheers

[Nigel]

... Any ideas why I would measure 500mv between dc ac earth? ...

Because the AC earth will be grounded on the pontoon. Your DC negative may be bonded to the keel, or other underwater metal. Two dissimilar metals in salt water equals a galvanic cell. This is why I think connecting battery negative and AC earth is a bad idea.

[Kaptajnen]

The reason (for the 500 mv reading) might rpt might be that when the hull of your boat is immersed in salt water, you get a stray current between the shore connection and the anode, perhaps from a nearby boat in the marina that also is connected to shore power.

Do you have a galvanic isolator installed in your shore power connection? That might eliminate the problem...

A check of your boat's wiring by a ABYC certified electrician might also be a good idea...

[Odysseus]

http://www.safeshoremarine.com/

Stray current s, read all about them.

Odysseus
Bav 38

[CRYSTAL]

The reason (for the 500 mv reading) might rpt might be that when the hull of your boat is immersed in salt water, you get a stray current between the shore connection and the anode, perhaps from a nearby boat in the marina that also is connected to shore power.

Hi,
I would agree but I don't have a hull anode. Only anode is on the SD130 and that's electrically isolated.

Also thanks to the link for safeshore... I've seen thanks  prior links.  Very nicely explained and hot topic on all forums regarding dc ac bonding.

I will 2x check again dc ac earth connection while I remove completely the sp connection. I'm pretty sure dc- is not bonded with keel.

Regards

[Kaptajnen]

Sorry, but I guess I was not clear in my post.

The stray current is (probably) between the Anode on the Sail Drive and the Marina's power system when you are plugged in to shorepower. That can happen even when the sail drive is electrically isolated.


That is why a galvanic isolator is a good idea for any boat connected to shore power.