35-3 Electrical Current

dsdemarest · Sep 27, 2013

I have a 1986 Ericson 35-3. In the course of chasing down and resolving an electrical problem, I discovered that I have what appears to be stray DC current between the mast and keel bolts. Here are some specifics:

Shore power off and DC breaker off.
Batteries disconnected on both positive terminals (two banks) and the ground
Current varies, but when checked late today showed .6 volts between mast and keel bolts. At same time read .7 volts between shrouds and water.
Boat is moored in salt water (Everett).

Any ideas as to cause (current in water?) will be appreciated. Also, is there a concern and what, if anything, should be done about it?

Thanks!

exoduse35 · Sep 27, 2013

That is exactly why you keep good zincs on the boat. It is not unique to your boat and you can have a bit of fun playing with dis similar metals and salt water making all kinds of batteries. It is not a good thing, but it is the thing. You can remove all the batteries and shore power from the boat and still have power! now if we could only harness it for a better use than rust and corrosion! Edd

Emerald · Sep 27, 2013

In addition to the dissimilar metals in salt water being a home made battery, I'd also look at stray current in your marina. While not the exact same scenario, I was able to drop a lead from my multimeter into the water and have the other end on a water pipe on the pier and read voltage. I was eating through 2-3 zincs a season. I put a galvanic isolator on, and my zinc eating problems went away. I had a diver do a bottom clean a few weeks back, and his report was that my zinc was like new and he didn't put on the one I had provided. She's been in the water two seasons without a haul out (haul out now due this year).

lbertran · Sep 27, 2013

Stray Current in Marina

I had a problem with stray current eating zincs. When our marina replaced the main pier last winter, they discovered a live electrical junction box right in front of my slip that was underwater during especially high tides. That problem was corrected and I also installed a galvanic isolator. I just had a diver clean the bottom and email me that he didn't need to replace the zinc as it was still at "80%+". The take away from me is that even if your own marina doesn't have elelectrical problems, if you cruise to other marinas and use shore power you'll find a galvanic isolator cheap insurance.

Christian Williams · Sep 27, 2013

Galvanic isolator here, too.

dsdemarest · Sep 27, 2013

Original post follow-up

Given the comments on stray current, zincs, and galvanic isolators, I might also add this "investigation" started when I noticed what appeared to be some detioration on my standing rigging (turnbuckles) which was new last fall. I sent a photo to the rigging company and they forwarded to the vendor. Here is their response:

 [FONT=&quot]"The rust patches are on our body and the swage stud (which is not ours by the numbers etched on the side.) This suggests a serious electrical leakage on the mast which is acting like a mini electroplating plant."

[/FONT][FONT=&quot]The boat does have an isolator, and zincs were replaced last spring. There are three - two on the shaft and one on the MaxProp. Mast has an anchor light, foredeck light, steaming light, and VHF antenna. When boat is not in use, DC power is off.

Thanks for the comments so far!
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Carefree Sailor · Sep 27, 2013

Recommendation for galvanic isolator?

My E35-3 is in San Diego and my diver replaces the zincs three times a year. Maybe it is time for me to consider installing a galvanic isolator. I would be interested in any recommendations as to whose product to consider. Or does it not matter -- one brand is as good as another?

Emerald · Sep 27, 2013

I found there were several brands all around the $200 price point. I decided I'd take a different approach to buying one, and started to call around and ask where they made them and where they were designed. Unless something has changed, NewMar is still designing and making their stuff here, and I was able to talk to an engineer about what I was doing and I have had some other NewMar products that I feel they have given great support on. So, I'd vote to help support one of our last surviving American marine companies:

http://www.newmarpower.com/AC_Shore_Power_Accessories/AC_Shore_Power_Accessories.html

(I bought mine from Defender)

:egrin:

Christian Williams · Sep 27, 2013

Regarding the reality of stray currents, I can't resist retelling a story from this pre-hack thread.

As a kid on Barnegat bay, we used to swim off a dock in Normandy Beach. Never mind the abundance of blue claw crabs or the thick schools of shiners or the dinner-size flounder you stepped on or any of that, which we took for granted.

This dock was special.

As you waded towards it, 100 feet away a tingling began. As you got nearer, it became more intense. WE had contests to see how close to the dock you could wade, and nobody ever made it all the way. The tingling progressed until it was a jangling all-body experience--like being electrocuted. We'd be wading and screaming while the others cheered us on, and then, nearly paralyzed, turn and stagger back to the normal water.

We didn't care what it was, it was cool.

Now I have a pretty good idea....

Stu Jackson · Sep 28, 2013

One thing to be careful with with galvanic isolators: almost all of the older ones didn't have any indication that they had failed!!! When purchasing, make sure you get one that has an indicator showing it is funcvtioning properly, something some newer models just started using within the past one or two years only.

lbertran · Sep 30, 2013

Galvanic Isolator Choices

I worked with Peter Kennedy Yacht Services in Annapolis to try to resolve my boat's stray current issues last winter. Below is a link to the galvanic isolator that he recommended and which, after vetting, I decided to install. If you already have a galvanic isolator and you're having stray current problems, you may need to buy or borrow a test electrode and methodically go through your boat testing for the source of the stray current. This is also a good way to test periodically to make sure your isolator is still doing its job. Good luck.

http://www.shop.pkys.com/DEI-Marine-Fail-Safe-Plus-30-Amp-Galvanic-Isolator_p_975.html

Loren Beach · Sep 30, 2013

For that kind of (serious) money, this might be an alternative:
http://www.imarineusa.com/charlesis...0240vac.aspx?gclid=CM7y1Nyz87kCFWuCQgodeDYAMQ

Loren

ps: pretty good discussion of galv. Isolators in this prior thread. Some of the embedded links may or may not work these days, tho.
http://www.ericsonyachts.org/infoexchange/showthread.php?6683-Galvanic-Isolator-confusion

jreddington · Nov 3, 2013

Here is a link to a manufacturer:

http://www.deimarine.com/

The D in DEI is actually Dairyland. Company's orignal product was to protect against stray current at dairy farms. Turns out cows don't produce as much milk when their udders "tingle".

A recent change in ABYC E-11 allows for "fail safe" galvanic isolators. Previous standards required indicators. These were frequently not installed, installed in non-visible locations, and ignored or not understood by boat owners. Installation of the fail safe units is much more straightforward. Just splice into your grounding conductor.

Present standards permit these LISTED fail safe units. Note that fail safe indicates that the unit maintains PERSONEL safety by maintaining continuity to ground. Failure DOES result in loss of galvanic protection. The units should be tested a couple times a season. Easy to check with a voltmeter. Instructions are included with the unit. Keep them handy if you don't think you"ll remember how. Some are now coming with simple built-in, push button testers.

Pick a unit sized based on your shore power capacity.

Also, in the latest revision of E-11, an Electrical Leakage Detector is now required on all new boats. This is lke a whole boat GFI with a trip level od 30 mA. For older boats, you can use one that fits on your shore power cord. If doing a major electrical refit, consider incorporating an ELD in your main panel. Don't be suprised if the boat trips it. In a recent personal non-scientific survey of a local marina, I found over 20% of boats with leakage over 30%.

If you have a clamp-on ammeter and know how to use it, check a few boats in your marina. It may open up your eyes to the danger lurking just off your pier for swimmers or someone falling in. Raise awareness. I'd love the day when yards test themselves and disconnect and "red tag" leakers or install ELDs on their pedestals. Australia already includes this in their electrical code foe marinas.

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35-3 Electrical Current

dsdemarest

Member I

exoduse35

Sustaining Member

Emerald

Moderator

lbertran

Member III

Christian Williams

E381 - Los Angeles

dsdemarest

Member I

Carefree Sailor

Member II

Emerald

Moderator

Christian Williams

E381 - Los Angeles

Stu Jackson

C34IA Secretary

lbertran

Member III

Loren Beach

O34 - Portland, OR

jreddington

Member III