Galvanic corrosion through shore internet hookups

[Gus_Honeybun]

I'm due to start living fulltime on my yacht and would like to have a broadband or ISDN internet hookup. However, i've been told that the hookup will circumvent my galvanic isolator and lead to corrosion. Does anybody have any idea if this is true or any other advice? Thanks for your help!

 

[ccscott49]

It will not cause galvanic corrosion, there is no direct connection, between a telephone line and computer and the mains or battery system of your boat. IMHO

 

[graham]

Gus Are you the Gus Honeybun who was at one time a diving supervisor . If so I was one of your gang ,if the names Ui , Harry the Bas!4r& , Jano and Naps ring a bell get in touch.
If not sorry but I dont know much about electrolosis .

PS In another life I was Taff H.

 

[bedouin]

I think it depends a lot on the details of the installation. If you are connecting your boat ground to an external "earth" potential then there is the theoretical possibility of galvanitic corrosion - certainly my broadband connection at home has an "earth" potential that is connected (by a convoluted path) to my mains earth.

If your on-board computer is a laptop then there will certainly not be a problem - since the computer 0V is not connected to "mains" earth. With a conventional desktop there is more chance of problems.

The other side of the equation of course is whether the signal 0V is connected to the water in the vicinity - which is also somewhat unlikely unless your neighbour on the pontoon is also connected to the same service.

Pragmatically I wouldn't worry about it too much - just keep your eye on your anodes and investigate further if they start disappearing fast!

 

[ccscott49]

Even desk top computers are powered through a transformer internally, so no direct connection takes place.

 

[jfkal]

Wrong. The housing is grounded.

 

[ccscott49]

Yes, your right!

 

[Buck]

Re: Galvanic corrosion through shore internet hook

Very unlikely, sounds like scaremongering. Did the advisor have a liking for wooden boats and a suspicion of electrickery and other works of the devil perchance?

Buck

Urrrgh.

 

[bedouin]

Wrong

In desktops the 0V is connected to chassis ground - which is itself earthed, so there is a direct connection between the 0V on the motherboard and the mains earth circuit.

 

[ccscott49]

Read the thread, I've already been told that, thankyou! But I still say it's highly unlikely, unlikely enough to forget it. IMHO

 

[bedouin]

I agree, as I said. But it would do no harm to keep an eye on the anodes just in case!

 

[ccscott49]

I do that anyway, but I also ensure, that none of my mains power is connected to my anodes/engines or anything else. My mains system is totally insulated from the boat, as is my 24 volt system, having insulated returns from all engine components and domestic components, some say this is wrong, I'll stick with it, as it is and has been on every boat I've owned. As an additional benefut, everything under the water, or connected to it, is bronze, including the shaftys and props, the guy spent a lot of money on Englander.

 

[Julian]

I designed some equipment for connection to telephones lines some years ago and I remember there was a requirement that there had to be isolation (i.e. a transformer or similar) between the equipment and the telephone line. This was to protect the telephone company emplyees from electric shocks from consumers equipment. This would also imply that there should be no leakage current causing corrosion.

 

[Guest]

Not sure I agree totally. Some external modems are isolated using a small transformer but I'm not too sure about the internal modems on laptops If in doubt there are quite cheap phone line isolators that will solve the problem.

Alternatively you could get one of the gyroscopically alligned satellite dishes they had on the recent round the world race. They're only about $200k and 4 feet wide so you shouldn't have any trouble fitting it in.

 

[ccscott49]

Read the rest of the thread, you're a little behind the times!!!

 

[Guest]

I did read the rest of the thread and the only one that mentioned isolating the phone line was Julian but even that didn't mention commonly available modems or laptop modems. Most laptop power supplies are switching power supplies these days as are the majority of PCs as well. The isolation varies depending on the brand so there is no guarantee that they are isolated by a transformer. We used to build switchers for various things and some had isolation some didn't. With products that are double insulated it is not essential to have ground planes that are isolated.

I haven't looked at circuit diagrams for the built in modems in say the laptop I am using right now but knowing these are built down to a price I can only assume that isolation is possibly not there.

I was simply pointing out that all the worry can be removed by putting in a phone line isolator and making sure all the usual steps are taken with regards to isolating the normal ground loops that can take out the anodes as well.

Cheers

 

[ccscott49]

Sorry, I had already been told this at least twice and I admitted I was wrong to think there was no direct connection twice, I don't need telling again, I get the message!

 

[Guest]

No worries, I'd be way worse than you if I was stuck on one of those oil rigs!!! I honestly don't know how you can cope except an enormous quantity of booze. I'd be pissed 24hrs a day. Tell me when the supply ship comes out what is the proportion by volume of food to booze? 10:1 is my guess?

Cheers

 

[ccscott49]

No booze on oilrigs, can you imagine somebody with a hangover, operating a draworks that picks up 1000 tons? or Drilling into another well producing 10,000 barrels a day at 5000 psi? No! Me neither!!
By the way, what the hell do you mean by way worse than me?? All I said was I'd been told!! If you had looked at the dates and times of the other threads, you may have noticed this, mind you I often miss that aswell, I don't understand your thinking on this, "I'd be way worse than you!"
Bye.

 

[Guest]

Yeah you're right, sorry, I meant absolutely no ill feeling. I just read between the lines and thought you were being a bit grumpy but I guess I was just expressing my own grumpiness after a s*%t day dealing with grumpy customers......goddam if only we didn't need customers!!!!

As for being anywhere with out booze, now I am REALLY humbled. I can't think of any other way to do that sort of job other than with a hangover......

Cheers