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Old 03-28-2016, 08:28 PM   #21
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when the zincs die the metal on the boat builds a "large" dc potential. That potential closes it's loop with other boats via the earth ground to ships dc ground connection.

Isolators break that path, and prevent other boats from eating yours.

Right?
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Old 03-28-2016, 11:33 PM   #22
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[QUOTE=Steve DAntonio;427490]
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Spot on and well said. For marinas installing leakage protected shore inlets, these are referred to as ELCIs, equipment leakage current interrupter, they are differentiated from conventional GFI receptacles, which trip at 5-7 mA, by their significantly higher trip threshold, which is 30 mA. .
Steve, Thrilled that you replied, and thanks for the kind words. I first became aware of the new Equipment Leakage protected inlets in Ketchikan Ak when I couldn't plug in with out tripping the breaker. At the time I suspected that they had used conventional GFI's with a low trip threshold causing nuisance tripping. I saw what looked like a standard GFI in the power tower, but I now wonder if it really was a ELCI instead. Can you tell the difference by looking at the breaker without taking off the cover? Are ELCI's the only way to meet the new code requirements for new or rewired marinas? I suspected my leakage to be under 10mA, but now I wonder if it's higher, time to do some investigation I guess. Last question, any publication date yet for your book?.............
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Old 03-29-2016, 02:34 AM   #23
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My thoughts have been that since my boat is all run on DC other than the battery charger, so there is no need for a galvanic isolator.
The CITEK charger has no AC ground connection to marina power.

Am I correct in this assumption?
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Old 03-29-2016, 06:18 AM   #24
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[QUOTE=Arctic Traveller;428309]
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Steve, Thrilled that you replied, and thanks for the kind words. I first became aware of the new Equipment Leakage protected inlets in Ketchikan Ak when I couldn't plug in with out tripping the breaker. At the time I suspected that they had used conventional GFI's with a low trip threshold causing nuisance tripping. I saw what looked like a standard GFI in the power tower, but I now wonder if it really was a ELCI instead. Can you tell the difference by looking at the breaker without taking off the cover? Are ELCI's the only way to meet the new code requirements for new or rewired marinas? I suspected my leakage to be under 10mA, but now I wonder if it's higher, time to do some investigation I guess. Last question, any publication date yet for your book?.............
I can't say for sure (although I was at that marina last year I don't recall the breaker arrangement) what they are using. Typically, a GFI is in a common receptacle form, like you'd have in your galley or bathroom at home. Those are often used on power pedestals, however, they are isolated, meaning they protect only what's plugged into them, not the shore cord, and they are limited to 15 and sometimes 20 amps. Trip threshold is 5-7 mA. Again I couldn't be sure without seeing the pedestal.

An ELCI looks like an actual circuit breaker, with an added component which monitors for an imbalance on the supply to the shore power inlet and opens the breaker at a designated trip threshold. Most boats have enough collective faults aboard, damp insulation, fluorescent ballasts etc, to trip a common GFI if you actually could plug the whole boat into this wall receptacle-like plug, whose threshold is just 5-7 mA, but there's no way to know for sure what your leakage is without measuring it, so that's an assumption that shouldn't be made, 8 mA may trip a GFI, but you may have 800 mA of leakage. Again worth a test. The cord leakage test must be carried out with power supplied to the boat, and again with the shore cord plugged in but main dock breaker off, to determine if the source of the leak is your boat or one nearby. This PowerPoint walks you through the process. http://www.boatus.com/seaworthy/asse...ock-safety.pdf

ELCI breakers look different, in addition to the normal breaker portion, they will also have a test button right next to the breaker handle, and some will also include status lights. ELCI incidentally is the term used for these devices when installed aboard a boat, and they are set to trip at 30 mA for ABYC compliance. When installed ashore, at the pedestal for instance, or elsewhere on the dock, they are referred to as Ground Fault Equipment Protective Devices (GF-EPDs), and some other similar names. Per NEC, the trip threshold at the marina or dock main supply breaker may be as high as 100 mA, but typically, if they are at the pedestal (that's preferred because if that breaker trips you know the source of the trouble, the boat that's plugged in to it) they are 30 mA. If that's the case in Ketchikan, and your boat is causing the pedestal breaker to trip, you should investigate and find the cause.

Probably more than you wanted to know.
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Old 03-29-2016, 06:35 AM   #25
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My thoughts have been that since my boat is all run on DC other than the battery charger, so there is no need for a galvanic isolator.
The CITEK charger has no AC ground connection to marina power.

Am I correct in this assumption?
Once you plug into shore power, regardless of the loads aboard, your vessel's underwater bonded metals are (or should be) now connected to AC safety ground wire in the shore cord, which is connected to the dock AC safety ground, which is then connected to the shore cords and AC safety grounds of all other boats that are plugged into shore power as well. In short, you are all connected and your zinc anodes may be protecting the underwater metals of the boats adjacent to you (provided they too have no galvanic isolator), regardless of what AC power you are using aboard. In fact, if you plug into shore power and never turn on the dock pedestal breaker, you are still connected in this fashion because the AC safety ground is never (supposed) to be switched or disconnected as long as you are plugged in.

Therefore, if you want to inhibit potentially harmful galvanic voltage flow, and corrosion, you should have a galvanic isolator. Every vessel's shore power system should have one.

Now on to your comment about he charger not being grounded. If I understand you correctly, if the charger has no AC safety ground connection, its plug has only two prongs? If so, it is double insulated and needs no third ground prong on the plug. (The CTEK charger appears to be designed for automotive use). Regardless, the vessel shore ground/corrosion connection issue remains as long as you are plugged into shore power, one that would be mitigated by a galvanic isolator.
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Old 03-29-2016, 06:06 PM   #26
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Probably more than you wanted to know.
No, that's exactly what I wanted to know, thanks and sorry for running this thread off the rails. Back to premature zinc failure.............
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Old 03-30-2016, 07:09 PM   #27
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That only happens to younger boats.
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Old 03-30-2016, 07:17 PM   #28
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Zincs on my boat are degrading faster than I anticipated. I am relatively certain there are stray currents in my salt water marina.

I understand the whole subject can be complicated, so I am limiting this initial inquiry to one single element of the overall puzzle:

If my boat is the one leaking AC (or DC) current to the water, will installing a galvanic isolator on my own boat be of value?
It is very unlikely that the issue is stray current unless the anodes are disappearing in a matter of days or maybe weeks. Stray current is a very quick process while galvanic corrosion is much slower.
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Old 03-30-2016, 08:52 PM   #29
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That is just the piece of info I needed. Thanks.
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Old 03-30-2016, 10:32 PM   #30
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It is very unlikely that the issue is stray current unless the anodes are disappearing in a matter of days or maybe weeks. Stray current is a very quick process while galvanic corrosion is much slower.
Well, that's true sometimes, but it totally depends on the AMOUNT of current. Any amount of current will degrade your zincs, it's why they are called sacrificial anodes. If they become insulated from the metal they protect, they will last forever, but provide no protection. the higher the current is, ithe faster the zincs are wasted. The corrosion rate is dictated by the current that is produced.
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Old 03-30-2016, 11:02 PM   #31
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Well, that's true sometimes, but it totally depends on the AMOUNT of current. The corrosion rate is dictated by the current that is produced.
Yes, the amount of current dictates the corrosion. In galvanic current you are talking about milliamps and stray current you are talking about amps, sometime very high amperage. I've never seen stray (leaking) current in the milli range.This is a clearly recognized difference in any corrosion analysis course you may take.

PS. I'm an ABYC Certified Corrosion Analyst.
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Old 03-31-2016, 12:17 AM   #32
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Haven't seen isolation transformers in the thread. But did just take a quick look through..

Still, heavy and noisy.? Always talked about one as a dock box. Being a liveaboard.

Kinda small amps for my needs but sure changes the game.

Random thoughts
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Old 03-31-2016, 12:33 AM   #33
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Newer isolation transformers from Magnum Energy are light 7-8 lbs for 30A and quiet from what I hear.

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Old 03-31-2016, 01:09 AM   #34
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Yes, the amount of current dictates the corrosion. In galvanic current you are talking about milliamps and stray current you are talking about amps, sometime very high amperage. I've never seen stray (leaking) current in the milli range.This is a clearly recognized difference in any corrosion analysis course you may take.

PS. I'm an ABYC Certified Corrosion Analyst.
That's good to know. Since the OP wants to know if his zinc usage is abnormal, measurement of the current would tell us if it was Galvanic or stray current leakage. Thanks...................
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Old 03-31-2016, 02:02 AM   #35
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Not long after I bought my boat the marina advised that they had investigated a complaint about rapid zinc loss. The guy was several boats away from me. They checked each boat on the finger arm and said I was the problem, and asked that I get it fixed.

The issue turned out to be a jumper from ground to neutral on the switch that changed from shore power to gennies (2). Hard to find as the short wire jumper was only visible when using a mirror to see the top-rear of the switch.

During troubleshooting and testing we found that 50% of the AC was being returned via the water. Yes, we measured up to 15A going back when I was drawing 30A from shore power! Very glad to have found that problem and fixed it! During boat refit a Charles isolation transformer was installed....
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Old 03-31-2016, 06:27 AM   #36
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Newer isolation transformers from Magnum Energy are light 7-8 lbs for 30A and quiet from what I hear.

Tom
Where are you seeing these, Tom? A quick Google search isn't turning up anything from ME. Thnx.
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Old 03-31-2016, 07:21 AM   #37
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That's good to know. Since the OP wants to know if his zinc usage is abnormal, measurement of the current would tell us if it was Galvanic or stray current leakage. Thanks...................
Only takes a minute with a clamp meter.
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Old 03-31-2016, 07:32 AM   #38
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Not long after I bought my boat the marina advised that they had investigated a complaint about rapid zinc loss. The guy was several boats away from me. They checked each boat on the finger arm and said I was the problem, and asked that I get it fixed.

The issue turned out to be a jumper from ground to neutral on the switch that changed from shore power to gennies (2). Hard to find as the short wire jumper was only visible when using a mirror to see the top-rear of the switch.

During troubleshooting and testing we found that 50% of the AC was being returned via the water. Yes, we measured up to 15A going back when I was drawing 30A from shore power! Very glad to have found that problem and fixed it! During boat refit a Charles isolation transformer was installed....
Neutral/ground connections are the cause of ESD (electric shock drowning) and is the very first electrical check I make when doing a survey. Very easy .....
- disconnect shore power
- turn off inverter
- turn off generator breaker
- turn on all AC breakers
- set multi meter at ohms
- measure resistance between neutral (widest prong) and ground ( prong with hook)

you should see O.L. (open line) on the meter if you see numbers and the ohms symbol, call a marine electrician.
-
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Old 03-31-2016, 07:37 AM   #39
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got some info and a a lot of photos of electrical problems on this web page.
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Old 03-31-2016, 07:40 AM   #40
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Newer isolation transformers from Magnum Energy are light 7-8 lbs for 30A and quiet from what I hear.

Tom
As far as I know Magnum does not offer a shore power transformer (transformers can be wired as isolation or polarization, it's the same transformer, only the wiring method differs, only when wired in isolation mode does it eliminates corrosion induced from other vessels, bulkheads, docks etc). Charles is the only iso xfmr manufacturer whose product meets current ABYC standards (which includes a UL Marine Listing) in E-11. They are heavy, by necessity there's no way around that as long as it's a transformer, and they generate heat and therefore need ventilation, however, I don't find them particularity noisy especially if soft mounted.

Bottom line, however, this is the most effective means of preventing galvanic corrosion and even stray current corrosion, the latter when it originates from a neighboring vessel. It will do nothing to mitigate stray current corrosion that originates aboard your own vessel. Stray current corrosion from neighboring vessels, while far less common, does occur, I've encountered it.
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