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Old 06-01-2011, 09:00   #31
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And what is the downside to adopting the European practices unilaterally for your own boat as it relates to using marinas/shore power with US standards and GFI's? And parking next to someone else's boat whose electrical systems are not up to any standard?
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Old 06-01-2011, 09:07   #32
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And what is the downside to adopting the European practices unilaterally for your own boat as it relates to using marinas/shore power with US standards and GFI's? And parking next to someone else's boat whose electrical systems are not up to any standard?
If you boat is completely isolated from the dock and has no long underwater circuit paths (no bonding) then it doesn't matter what the boats around you do. As I describe in my article on Bonding and Corrosion, you are only going to be harmed from the boat next to you if you are either 1) connected to it through shore ground or 2) intercepting currents between two other boats that are connected through shore ground. This only happens if you have bonded underwater metal that can intercept the current between those two boats. The analogy is to think of the blackbird sitting on the 20,000 volt power line. As long as that bird is isolated, he is fine. It is the eagle whose wings span both that same wire and a ground wire that is in trouble.
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Old 06-01-2011, 09:36   #33
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This is a rather convoluted and twisted discussion mixing AC wiring and Electrolysis protection with short circuits and leaking AC circuits both in the marina and adjacent boats. By mixing it all together you can get rather confused. They are really separate, but associated topics.
- - It is my understanding the "RCD" is merely Euro-speak for USA GFCI circuit breaker (Residual Current Device). It detects the current entering the device as un-equal to the return current (neutral) and disconnects the circuit. Obviously electricity is "leaking" to somewhere else. It could be through a human with one hand on the appliance/power cable and one foot in a bucket of water (so to speak). The result can vary from curled hair to worse. Or electricity could be leaking back into the earth ground wire (green) but not sufficient to trip the circuit breaker.
- - It is this stray leaking current in the earth ground (green wire) that is of special concern to boaters. Typically to save money, the manufacturer connects the AC earth ground wire to the engine which is in turn connected to the propeller shaft and propeller. Secondarily the "bonding system" of all other metal on the boat - stanchions, chain plates, metal through-hulls, etc. is also connected to the engine, et. al.
- - This minute stray current leakage provides the necessary energy to start and accelerate electrolysis in your propeller and other fittings exposed to sea water (salt water) and they start to be eaten away or de-alloyed. Zincs go first, but soon after the propeller and bronze through hulls follow.
- - It is all too common in old and less maintained marinas for the shore power systems to have disconnected earth grounds or inadequate wiring. Some of it fried and burnt by old cases of dead shorts - and the wires never repaired or replaced. So you end up with all the boats connected to shore power being "earth-grounded" together. A neighbor boat with a "leaking AC" system will end up sending that electrical current to your boat and system.
- - 1. You have "earth ground" green wire to protect appliance dead shorts and enable the C/B to trip. 2. You have "earth ground" wire to protect humans from being a surrogate earth ground. And 3. you have "earth ground" isolation from faulty shore power to protect your boat's underwater metal from being electrically dissolved.
- - Others have spoken to the particular ways to accomplish protecting you and your boat.
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Old 06-01-2011, 11:28   #34
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... I'll give you the near universal European practice ( arguably an area with more safety rules then anywhere on the planet)...
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@Dave Sounds like an excellent approach. Do you have a standard that lays this all out? ...
See the European Standard:
Small craft - Electrical systems - Alternating current installations
EN ISO 13297:2000 (ISO 13297:2000)

Here ➥ http://www.sychut.com/nav/el/ISO13297.pdf

Which states, in part:

“... 4.2 The protective conductor shall be connected to the craft's d.c. negative ground (earth) as close as practicable to the battery (d.c.) negative terminal.
NOTE If an RCD (whole-craft residual current device) or an isolation transformer is installed in the main supply circuit of the a.c. system (see
8.2), the negative ground terminal of the d.c. system need not be connected to the a.c. shore ground (protective conductor) ....

... 4.8 The neutral conductor shall be grounded (earthed) only at the source of power, i.e. at the onboard generator, the secondary of the isolation or polarization transformer, or the shore-power connection. The shore-power neutral shall be grounded through the shore-power cable and shall not be grounded on board the craft ...
... 8 Ground-fault protection/earth-leakage protection

... 8.1 GFCIs (RCDs) shall be of the trip-free type.

8.2 The craft shall be provided with earth-leakage protection in the main supply circuit by
a) a double-pole RCD having a maximum nominal trip sensitivity of 30 mA and 100 ms maximum trip time located in accordance with 7.2.2, or
b) each receptacle located in the galley, toilet, machinery space or weather deck shall be protected by a GFCI (RCD) having a maximum sensitivity of 10 mA.

8.3 The GFCI (RCD) device shall have an internal circuit for manual testing of the trip function.
NOTE GFCI (RCD) double-pole receptacle (socket) devices may be installed as part of a convenient outlet installation, either in single-outlet applications or in multiple "feed through" installations, i.e. a series of receptacle (socket) outlets connected in parallel such that the first GFCI (RCD) protects everything in the circuit ...”
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Old 06-01-2011, 11:38   #35
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Actually, in terms of damage to your boats that are connected to marina ground some of the worst damage can come from the DC+ on some boat being connected to the ocean, for example if the ground to the engine is removed for some reason and the DC+ connects to the engine this will put the prop at DC+ with another boat at DC- (if AC ground is connected to DC- on both boat) and you have a 12 drive for metal to leave one of the boats. I think that is one of the main reasons not to connect to marina ground. The really nasty side line on this is if your boat is isolated but bonded, it can participate in this same reaction by having two bonded through hulls grab some of the underwater current.

I think this is a very complex topic and leads to much confusion.
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Old 07-01-2011, 06:41   #36
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@Dave Sounds like an excellent approach. Do you have a standard that lays this all out?
In Australia the Australian Standard AS3004 (Electrical Installations- Marinas and Pleasure Craft at Mains Voltage) applies. The Standard try to keep up with progress.
The Standard can be downloaded at a cost.
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