Electrolysis Question

mtullier · October 14, 2013, 07:14:10 PM

Question for the electrical engineers..Lots of stray current in my current marina. Does the electrolysis potential decrease if I leave the 110 power unplugged?

lazybone · October 15, 2013, 03:55:24 AM

How does one tell if there's lots of stray current in their marina?

patrice · October 15, 2013, 06:06:35 AM

Hi
When you put your toes in the water and it tickles .....

mtullier · October 16, 2013, 06:54:15 PM

Opinions are also welcome. Does anyone have experience with this? I plan on doing an experiment by measuring the metal loss on an anode with and with out the shore power plugged in.

Stu Jackson · October 16, 2013, 07:07:33 PM

Quote from: lazybone on October 15, 2013, 03:55:24 AM
How does one tell if there's lots of stray current in their marina?

You read Nigel Calder's book, Boatowners Manual for Mechanical and Electrical Systems and learn how to do it. Too long to re-type here and requires diagrams. That are available in the book.

mtullier · October 16, 2013, 07:43:10 PM

Thank you Stu. I'll check it out.

Ron Hill · October 17, 2013, 02:46:59 PM

Guys : Maybe I'll hear from Mainsail, but I've had no problem as I've always had a flexible coupling. The engine and shaft/prop are isolated - not grounded to the water.

My thought

stevewitt1 · October 18, 2013, 07:22:26 AM

QuoteWhen you put your toes in the water and it tickles .....

WOW, I can't believe how many boaters there are, even today, that feel it's OK to swim around docked boats. (Don't get me wrong, I am, in no way, inferring that mtullier was suggesting that it's OK) That "tickle" could easily result in people drowning. I'm not anything close to being an electrical engineer but I won't even swim off my boat if my inverter is running while on the hook!

Steve

visit us at www.ocontoyachtclub.com and www.warbirdsix.com

scotty · October 18, 2013, 10:07:32 AM

My understanding is that swimming near electrical sources can be very dangerous in fresh water. In salt water this is not the case. Please correct me if I have this wrong.

Mike and Joanne Stimmler · October 18, 2013, 10:52:37 AM

I think it would be dangerous under either conditions but even more so in salt water. It's my understanding that salt water is a better conductor than fresh water.
In fact, I used to think that electrolysis was not a problem in fresh water until I had an aluminum boat on a residential lake here in Arizona that was totally ruined by stray currents from the pumps for the fountains and waterfalls finding a ground through my boats battery charger.

Mike

Ron Hill · October 18, 2013, 05:23:33 PM

Quote from: Mike and Joanne Stimmler on October 18, 2013, 10:52:37 AM
I think it would be dangerous under either conditions, but even more so in salt water. It's my understanding that salt water is a better conductor than fresh water.

Roger that!!

scotty · October 18, 2013, 05:24:16 PM

Here is a link to BoasUS about this problem:

http://www.boatus.com/seaworthy/magazine/2012/october/Raising-Awareness-About-Electric-Shock-Drowning.asp

As you see, they contend that this is not a concern in salt water. " In saltwater, electricity does not cause ESD; saltwater is more conductive than the human body. There is not yet enough research to know at what point brackish water becomes dangerous".

This is an important safety topic. It might be a bit of thread drift, but it's worth it. Thanks for bringing it up.

Mike and Joanne Stimmler · October 19, 2013, 09:36:05 AM

Scotty.
Wow! According to your excellent article, my logic is backwards. I guess we all have a lot to learn. Even though salt water is more conductive, the human body is more conductive than fresh water seems to be the main point.
Thanks for shareing this with us.

Mike

Ron Hill · October 19, 2013, 01:44:05 PM

Guys : Salt or fresh, I still wouldn't recommend going in the water around a dock full of boats!!

Screw up boat wiring that will let stray DC current in the water can/could be worse than stray AC current!!

A thought

scotty · October 19, 2013, 10:49:19 PM

So ... this got really interesting. I read what Ron said, and that got me thinking (I always pay attention to what you say Ron, you've done a really good job through the years) ... I looked at a lot of websites - check out this ABYC lecture:
http://www.abycinc.org/whyabyc/esd_I.cfm

and found that while in most parts the problem is in fresh water, there are unusual, but lethal, circumstances where stray voltage is significant in salt water. If you directly touch an electrified object, or perhaps if you get really close. Rather than hijack this thread, I think I'll find more information on Electro Shock Deaths (ESD) and start up a new thread.

I also now know a lot more about what causes "hot" marinas. That brings us back to the original question of whether it is better to leave the boat unplugged.

There are a lot of people on this site who know more about this than I, so I'll stick my neck out and give my interpretation. Please correct my mistakes.

What causes "hot" marinas?: Poorly grounded circuits. Electricity going into the boat should equal the electricity coming out. If not, then it is going to ground through the water. The electricity going in is +, coming out is - and the safety ground. If there is a short in the system, the safety ground is supposed to return the electricity. If the ground is not working properly, it goes through the water.

How can you tell if your marina is hot?: I've had boats with zincs that last 6 months. My current slip they last 2 months. That seems "hot" to me. A current measurement is more accurate. The current in the positive should equal to the current in the negative and the ground. (current in = current out) You can use a clamp meter to measure the electrical cords in your marina - and in your specific area. A zero means no loss. A reading like 100 milliamps is potentially lethal (Call the harbor office). A reading like 10 is very significant and can also be lethal. I'm extrapolating that any measure like 1 or more can present galvanization issues for a boat. You can also measure the water by inserting an amp meter directly into the water (and connecting to ground) and measuring that.

Is it better to leave you boat unplugged? (the original question): If you have ground issues, Yes. Measure with the clamp meter. If not, should you unplug? I dunna know. Dude, It's 10:30 PM. I'm getting tired. Perhaps someone else has that answer, or I'll look later. You notice that I haven't talked about DC current loss.

Thanks for the stimulating posts, mis amigos. I learned a lot from your posts, and researching and posting this information. Hope this helps move the discussion forward. I'm still looking to the answer to the original question....

Scotty