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Old 08-03-2015, 23:24   #16
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Re: Stray voltage in a marina

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Old 09-03-2015, 11:07   #17
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Re: Stray voltage in a marina

You know I hadn't thought of this before now.... how about installing a Variac on a boat? A Variac is nothing more than a big AC transformer with the ability to adjust the voltage. The advantage would be that as it's a transformer, the problems from the marina power would not be passed along to the boat right? $50
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Old 09-03-2015, 11:55   #18
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Re: Stray voltage in a marina

Our marina manager has all the AC shore power cords from each boat checked for stray AC that might be caused by a particular boat. I used to use my clampon AC ammeter to go along and try to find a boat dumping AC in to the water. Normally there should be no reading since the AC in should be balanced exactly with the AC out on the hot and neutral wires in the cable. If some of the juice is not coming back it is going in to the water.

I have seen it with my own eyes and have seen boats disconnected from the pylons by the marina which would contact the owners and have them correct the problem on the problem boat. In the meantime, no AC for them.

There are more sophisticated testers which cost a lot. Our marina has one and uses it every 2-3 months on every shorepower cord. They also check for any stray current from the dock wiring.

From my limited knowledge you can also help your situation by using an isolation transformer provided it is wired and grounded to prevent this problem. Grounding of transformers is a area with many opinions as witnessed by many "expert" opinions on this board. For the sake of my health, safety, and mental well-being, I won't get in to that.
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Old 09-03-2015, 11:56   #19
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Re: Stray voltage in a marina

A Variac does not provide isolation because it is a one winding design. See autotransofmer here. Also, why would you want to introduce voltage variation?
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Old 09-03-2015, 12:23   #20
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Re: Stray voltage in a marina

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Originally Posted by St. Elsewhere View Post
A Variac does not provide isolation because it is a one winding design. See autotransofmer here. Also, why would you want to introduce voltage variation?
I agree that a variac is not a solution for isolation or voltage regulation.

Electricity and water can be a fatal mix and one either needs to know exactly what he is doing or follow accepted industry and ABYC standards. The person who knows exactly what he is doing will likely follow those standards.

As for the OP, does your boat have a galvanic isolator? Is it working correctly? Are you sure?
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Old 09-03-2015, 12:43   #21
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Re: Stray voltage in a marina

Quote:
Originally Posted by Cheechako View Post
You know I hadn't thought of this before now.... how about installing a Variac on a boat? A Variac is nothing more than a big AC transformer with the ability to adjust the voltage. The advantage would be that as it's a transformer, the problems from the marina power would not be passed along to the boat right? $50
SAFETY CAUTION. Not that simple an isolation transformer has be be specifically wound for that purpose. Most transformers share common neg/grounds and don't have full isolation between core and coils. this could lead to a variety of hazard conditions if you where unaware of it and thought the boat was isolated from shore power. I looked at UK work-site safety transformers for the same reason but they had no isolation. (also much heavier and less efficient than HF units made for the job)
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Old 09-03-2015, 13:32   #22
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Re: Stray voltage in a marina

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Originally Posted by exMaggieDrum View Post
Our marina manager has all the AC shore power cords from each boat checked for stray AC that might be caused by a particular boat. I used to use my clampon AC ammeter to go along and try to find a boat dumping AC in to the water. Normally there should be no reading since the AC in should be balanced exactly with the AC out on the hot and neutral wires in the cable. If some of the juice is not coming back it is going in to the water.

I have seen it with my own eyes and have seen boats disconnected from the pylons by the marina which would contact the owners and have them correct the problem on the problem boat. In the meantime, no AC for them.

There are more sophisticated testers which cost a lot. Our marina has one and uses it every 2-3 months on every shorepower cord. They also check for any stray current from the dock wiring.

From my limited knowledge you can also help your situation by using an isolation transformer provided it is wired and grounded to prevent this problem. Grounding of transformers is a area with many opinions as witnessed by many "expert" opinions on this board. For the sake of my health, safety, and mental well-being, I won't get in to that.
I would immediate leave any marina that was doing this because if you can feed more power into the boat than comes back on the nutral line it means the RCD is not working. Thats excactly what and RCD does and then shuts of the power if it detects an imbalance. Theses are fitted to every power tower. Most essential part of electrical safety and every boat should have one as well, close as possible to the shorepower input.
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Old 09-03-2015, 13:57   #23
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Re: Stray voltage in a marina

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Originally Posted by roland stockham View Post
I would immediate leave any marina that was doing this because if you can feed more power into the boat than comes back on the nutral line it means the RCD is not working. Thats excactly what and RCD does and then shuts of the power if it detects an imbalance. Theses are fitted to every power tower. Most essential part of electrical safety and every boat should have one as well, close as possible to the shorepower input.
Roland

You seem to take for granted that there is an RCD at every marina power pedestal. At least in the US marinas I am familiar with there are no RCDs in the pedestals. I am not saying that not having RCDs (or not vaccinating children) is a good idea, bit just the way it is in many places.

Also don´t ask me to explain why people get so fussed about hot-neutral polarity instead of making sure the green is at ground potential and there is an RCD.

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Old 09-03-2015, 14:13   #24
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Re: Stray voltage in a marina

So you have an AC ground plate under water. Guess where the current goes if you have a break in the AC ground wire anywhere in your cct.? I didn't see any mention of an ELCI.
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Old 09-03-2015, 14:30   #25
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Re: Stray voltage in a marina

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Is there a test for stray voltage? Our poor rudder cannot take much more....

If this subject has been beat to death elsewhere, just point me in the right direction. Thanks all.
Just disconnect the bloody thing from other submerge metal, from DC ground/engine and from AC green. That will reduce marina corrosion a lot. If some expert tells you that the rudder needs to be "bonded" say it is it not a contractor.

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Old 09-03-2015, 14:37   #26
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Re: Stray voltage in a marina

Just to make it clear, all NEW marinas in the US must have either whole dock or individual slip circuit interrupters as they do in the EU. It's very much in flux in the US and codes are being written, revised, delayed, implemented, delayed, etc.

Oh so much fun!
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Old 09-03-2015, 15:51   #27
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Re: Stray voltage in a marina

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Just to make it clear, all NEW marinas in the US must have either whole dock or individual slip circuit interrupters as they do in the EU. It's very much in flux in the US and codes are being written, revised, delayed, implemented, delayed, etc.

Oh so much fun!
Scott,

AFAIK NEC 2011 (#555.3) only requires "main marina feeder conductors" to have GF protection rated at no more than 100mA. Imagine what will happen if a ground fault in a boat that plugs in (not uncommon in a country where most boats and marinas do not have GF devices that will make the fault apparent) brings down the main supply to the marina!

Is that one more attempt to lead the public to believe that GF protection cannot be made to work, even if there are many countries that have done it? I am not a fan of conspiracy theories but I don´t think any other country could screw up the implementation of GF protection as badly as the US has done, even if they tired hard.

Are you saying that there has been a change since then and now they *mandate* GF devices in every pedestal or dock?

By the way, I watched a video of this Mike Holt "guru" guy who still does not understand that a 30mA GF device will trip fast enough to save people from dying. He is still hung up on the experiments of decades ago in which people where exposed to current for many seconds, not 1710th of a second.

Another story is that the way existing things are grandfathered in US codes you may have to wait a few decades for this half-a**ed attempt to implement GF protection a marina pedestals to be reflected in most marinas?

Please tell me that I have missed something.
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Old 09-03-2015, 15:57   #28
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Re: Stray voltage in a marina

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Scott,



AFAIK NEC 2011 (#555.3) only requires "main marina feeder conductors" to have GF protection rated at no more than 100mA. Imagine what will happen if a ground fault in a boat that plugs in (not uncommon in a country where most boats and marinas do not have GF devices that will make the fault apparent) brings down the main supply to the marina!



Is that one more attempt to lead the public to believe that GF protection cannot be made to work, even if there are many countries that have done it? I am not a fan of conspiracy theories but I don´t think any other country could screw up the implementation of GF protection as badly as the US has done, even if they tired hard.



Are you saying that there has been a change since then and now they *mandate* GF devices in every pedestal or dock?



By the way, I watched a video of this Mike Holt "guru" guy who still does not understand that a 30mA GF device will trip fast enough to save people from dying. He is still hung up on the experiments of decades ago in which people where exposed to current for many seconds, not 1710th of a second.



Another story is that the way existing things are grandfathered in US codes you may have to wait a few decades for this half-a**ed attempt to implement GF protection a marina pedestals to be reflected in most marinas?



Please tell me that I have missed something.

Yes the whole 30ma argument is over in the rest of the world. But in the US nonsense arguments are still advanced. With regard US code and GFI I'm reminded of , " yes it works in practice , but does it work in theory " !! Type of nonsense

Dave


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Old 09-03-2015, 17:28   #29
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Re: Stray voltage in a marina

<snip>
Are you saying that there has been a change since then and now they *mandate* GF devices in every pedestal or dock?
<snip>

555 is indeed the controlling code. Some marinas have met it by having whole dock ELCI's, indeed at 100ma (with varying trip timing). I haven't seen a 'whole marina' installation but have seen several whole dock installs. I agree, individual slip systems such as made by Eaton is the right way to go. The codes will catch up; I don't see conspiracy, just bureaucracy.

Several years ago ABYC required whole boat ELCI's but while 30amp units were quick to market
no manufacturer made a 50amp version (and most US Boats I see are 50amp 125/250v) so they kept pushing off the requirement. It took a couple of years for the market to catch up.
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Old 09-03-2015, 17:48   #30
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Re: Stray voltage in a marina

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<snip>
555 is indeed the controlling code. Some marinas have met it by having whole dock ELCI's, indeed at 100ma (with varying trip timing).
Varying timing? I wonder what are they trying to accomplish that they could not accomplish by copying the UK marina standard (TT earth + RCD at pedestal), which deals with the same reality very effectively with available equipment.
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