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Old 15-02-2012, 10:14   #31
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Re: A/C Wiring Short ?

I was using the same type of wording as ABYC, throughout "is" and "shall" are very common.

The reality though is that you have control over the wiring in your boat and there is no reason it cannot be safe.

You do not have control over the shore side.
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Old 15-02-2012, 11:24   #32
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OMG

There really should be no local AC protective earth to sea water ground. The common point where neutral and earth wire meet is the earth rod.

Abyc recommendations to connect ac earth to dc negative ( note this may or may not be dc "ground" ( whatever that is) are not done to ensure an alternative fault path for AC faults, it is to ensure that any AC that comes in contact with a purely DC device ( like your engine block) is included in the AC earth line protection and triggers fuses to blow.

In my opinion the European whole boat 30 ma ELCI ( RCD ) solution is better.

As to AC reverse polarity. It is absolutly the case that the boat must be at least safe in reverse polarity situations and in fact they are.

In some European codes the earth rod has disappeared and the ac earth is just connected to the ac neutral at the consumer Panel. The power company ensures the neutral is grounded , the net effect being the same

The ac earth is not designed to carry full neutral currents only fault currents. It is not a " backup " to a loss of neutral.

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Old 15-02-2012, 18:24   #33
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Re: A/C Wiring Short ?

Quote:
Originally Posted by goboatingnow View Post
OMG

There really should be no local AC protective earth to sea water ground. The common point where neutral and earth wire meet is the earth rod.

Abyc recommendations to connect ac earth to dc negative ( note this may or may not be dc "ground" ( whatever that is) are not done to ensure an alternative fault path for AC faults, it is to ensure that any AC that comes in contact with a purely DC device ( like your engine block) is included in the AC earth line protection and triggers fuses to blow.

Dave
Nigel Calder disagrees - from Professional Boatbuilder April/May 2006
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Old 16-02-2012, 06:42   #34
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Quote:
Originally Posted by mitiempo

Nigel Calder disagrees - from Professional Boatbuilder April/May 2006
That mag is aimed at a US audience , Calder says different things when addressing a European audience

Let's look at his claims.
1. Protects against ac leaks or breakthrough into DC circuit.
With the current standard low voltage devices, such a failure mode is highly unlikely, he mentions battery chargers. This is an old chestnut from the autotransformer days.

Fitting a whole boat ELCI fixes this

2. Lightening protection requires the grounds to held at the same potential ,

Absolute nonsense , no evidence presented.


Let's look at a European perspective

1. Whole board residual current detection. Generally trips on any fault where current does not return via neutral. Including swimmer in the water issues

2. Superior corrosion protection no leakage path of noisy ac earth into dc systems.

3. Quieter ac earth. No dc load dumping.

4. No inadvertent ac fault path through dc negative

5. non bonded boats common in Europe

6. No cross coupling of rf noise

Calder is not a reliable source on electrics he tends to parrot official stuff and does little from first principles. He's primarily a journalist.

The other point I made has nothing to this. What I said is the only path to ground for AC faults which are generated by shore power is back through the earth lead of the shore power. There should not be a separate AC ground either directly or via a DC negative to the local seawater. This is because you could set up an inadvertent AC fault path through the DC system or through the boat itself. ( via machinery etc) with some bad outcomes. Mains supply codes do not support multiple paths to ground.

My advice , the largest builder of boats on the planet can't be wrong. Fit a ELCI , break the Dc ac earth connection and live happily and safety thereafter. ABYC are just recommendation and in my view outdated.

Dave
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Old 16-02-2012, 07:33   #35
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Re: A/C Wiring Short ?

Sorry if I can't keep quiet here; GOBOATINGNOW you are right about fitting an ELCI (as I have pointed out earlier and this is now an ABYC requirement on all newbuilds built to the voluntary standards).

I have to respectfully disagree though on "Calder is not a reliable source on electrics he tends to parrot official stuff and does little from first principles. He's primarily a journalist."
Just a "journalist"? Are you kidding? That is insulting!
I worked with Nigel Calder; he is a brilliant technician! And, also has the talent to write it down! Good for him.
If you were boating 30 years ago, it was his Boatowners Eelectrical and Mechanical Manual that you took home and considered it the "bible".
He does not "parrot official stuff" - he wrote / was instrumental in creating many of our standards!

Please don't get me wrong, in my work I live with the codes of ABYC, NFPA, USCG, TTC, CCG and a myriad of Bureau of Veritas and other societies but I am not a fanatic. I always consider what works in real life and what is marketing.
Most of us realize that there is a good deal of "standards", especially when it comes to ABYC, that were derived from political or business models of alternative reasons but when it comes to the electrical and fuel handling standards, there is no room for conflicts of interest driven "official stuff". The builder of ELCI components may sit on the board of ABYC but we can all agree that the standards that are written have more merits than just selling a product.

I try to stay out of these discussions for good reasons and quite frankly, I think it is very dangerous to be giving advise or even discussing technical issues that we can not lay eyes and hands on.
Should also remember the old adage that little knowledge sometimes can equal to big danger!


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Old 16-02-2012, 07:54   #36
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Re: A/C Wiring Short ?

Quote:
I worked with Nigel Calder; he is a brilliant technician! And, also has the talent to write it down! Good for him.
If you were boating 30 years ago, it was his Boatowners Eelectrical and Mechanical Manual that you took home and considered it the "bible".
He does not "parrot official stuff" - he wrote / was instrumental in creating many of our standards!
I was boating 30 years ago, And I have several editions of the "Bible"

I disagree with several things he says and the conclusions he reaches, thats doesn't means he is or isn't brilliant. I have seen him write different things to different audiences. What I meant by a journalist, is he's in the business of being a self publicist.

I wasn't running him down, once you start writing to keep you in pennies, you go over to the dark side IMHO, but hey thats just me.
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Old 16-02-2012, 08:14   #37
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Re: A/C Wiring Short ?

When I see a post: "A/C Wiring Short ?", I think the best advise we can give to an owner who has no expertise to diagnose this kind of problem is to spend a couple of hours' labor dollars and leave it in the hands of a qualified tech.

This may be a good place to again, remind freshwater boaters of the dangers of Electric Shock Drowning (ESD).
Not long ago our industry was unaware of the cause of deaths around our boats and docks. Now we know what it is and learning about it can save lives!
Spending the money to retrofit an older boat with EFCI mains may be the most important improvements you can make on your boat today!

Please go to these links and learn about ESD now!
BoatUS.com - Seaworthy Magazine
Terry Gardner: Electric Shock Drowning: A Hidden Danger In Fresh Water
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Old 16-02-2012, 09:07   #38
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Re: A/C Wiring Short ?

Quote:
Originally Posted by goboatingnow View Post
That mag is aimed at a US audience , Calder says different things when addressing a European audience

Let's look at his claims.
1. Protects against ac leaks or breakthrough into DC circuit.
With the current standard low voltage devices, such a failure mode is highly unlikely, he mentions battery chargers. This is an old chestnut from the autotransformer days.

Fitting a whole boat ELCI fixes this

2. Lightening protection requires the grounds to held at the same potential ,

Absolute nonsense , no evidence presented.


Let's look at a European perspective

1. Whole board residual current detection. Generally trips on any fault where current does not return via neutral. Including swimmer in the water issues

2. Superior corrosion protection no leakage path of noisy ac earth into dc systems.

3. Quieter ac earth. No dc load dumping.

4. No inadvertent ac fault path through dc negative

5. non bonded boats common in Europe

6. No cross coupling of rf noise

Calder is not a reliable source on electrics he tends to parrot official stuff and does little from first principles. He's primarily a journalist.

The other point I made has nothing to this. What I said is the only path to ground for AC faults which are generated by shore power is back through the earth lead of the shore power. There should not be a separate AC ground either directly or via a DC negative to the local seawater. This is because you could set up an inadvertent AC fault path through the DC system or through the boat itself. ( via machinery etc) with some bad outcomes. Mains supply codes do not support multiple paths to ground.

My advice , the largest builder of boats on the planet can't be wrong. Fit a ELCI , break the Dc ac earth connection and live happily and safety thereafter. ABYC are just recommendation and in my view outdated.

Dave
Dave,

You keep mentioning this as if the ABYC has not adopted the RCD / ELCI standard. This has been pointed out to you, that they have adopted it, numerous times but you choose to selectively ignore it.

ABYC E-11 does include an ELCI/RCD device. That said 98% of boats in this country are built and wired for the old standard and our docks are "generally" (IMHO) very poorly maintained and the wiring can be suspect. Dropped AC grounds on the docks are not at all uncommon. I alerted one local marina of a dropped ground last June and as of early August it was still not fixed.

The ABYC PTC has been over and over the ELCI/RCD AC/DC grounding issue and, based on evidence, it was decided to keep the on-board AC/DC grounding connection AND use an RCD/ELCI device. I recently had conversations with both Ed Sherman and John Adey, of the ABYC, about this specific subject. For now the standard includes both an ELCI/RCD and AC/DC grounding on-board.

The ABYC standards are written for safety first and not around what will or will not corrode your boat faster as the first priority. Anyone plugging into dock power without an isolation transformer or at the least a galvanic isolator is, well, taking a HUGE risk in this country.

The PTC has made the decision to keep the AC/DC grounding and add the ELCI/RCD based on case evidence of failures of RCD/ELCI devices to fully protect as they are intended to. They have decided to keep the AC/DC grounding tie, for now, as redundancy to the ELCI/RCD. As we know all things electronic on boats can and do fail.
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Old 16-02-2012, 12:57   #39
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Re: A/C Wiring Short ?

Here's the data, look at it yourself

http://qualitymarineservices.net/ele...dent_list.html

In some of these incidents, it was shown that the AC/DC ground connection was the cause of death, and in some cases it was shown that the lack of an AC/DC ground connection was the cause. The ABYC wants you to make that connection based on the assumption of a proper path to ground on the AC groundwire, which experience shows is just not the case. The link cites inspections showing that 96% of the docks were not properly wired, with open grounds the most common fault.

However, in almost every case a RCD ON THE DOCK would have saved these people. Yet the latest codes for marina wiring only specify GFCI protection for "other than dock power".

I don't often agree with Dave, but in this case I'm with him 100%!
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Old 16-02-2012, 14:10   #40
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Re: A/C Wiring Short ?

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Originally Posted by donradcliffe View Post
... However, in almost every case a RCD ON THE DOCK would have saved these people. Yet the latest codes for marina wiring only specify GFCI protection for "other than dock power". ..
Wrong - the 2011 NEC requirement for the main overcurrent protective device to be GFCI-protected (with a max of 100mA).

From the 2011 National Electric Code
555.3 Ground-Fault Protection.
The main overcurrent protective device that feeds the marina shall have ground fault protection not exceeding 100 mA.
Ground-fault protection of each individual branch or feeder circuit shall be permitted as a suitable alternative.
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Old 16-02-2012, 14:49   #41
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Re: A/C Wiring Short ?

Jim Shafer led the crusade to include ground fault protection for dock power. Here’s a few articles he wrote.

"The Critical Ground System," James D. Shafer, Marina World, May/June 2004. Issue 31.
Explains the importance of marina bonding system and what part in plays in Galvanic / DC stray current corrosion and protection from AC ground faults.
http://www.halifaxharbor.net/Marina%...g%206%2004.pdf

"The Case of the Hot Marina," Jim Shafer, EC&M, April 2004, Vol. 103 Issue #4,
A story of the electric shock drowning of a mother and daughter. A classic example of the harm done by an undected AC ground fault in fresh water, combined with a missing ground conductor.
The Case of the Hot Marina

"Hot Marina Lethal AC Ground Faults,"
Jim Shafer, Mike Holt News Letter, Nov. 17, 2003
A true story of the electric shock drowning of a rescuer just after he saved a young girl from the same fate. Another classic case, freshwater, ground fault, missing ground conductor.
Hot Marina - Lethal AC Ground Faults
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Old 16-02-2012, 17:09   #42
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Re: A/C Wiring Short ?

Notwithstanding the new 2011 NEC requirement (555.3) for the main overcurrent protective device to be GFCI-protected; I wouldn’t expect your North American marina to be in compliance. As far as I know, this will only apply to new installations.
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Old 16-02-2012, 18:39   #43
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Quote:
Originally Posted by Maine Sail

Dave,

You keep mentioning this as if the ABYC has not adopted the RCD / ELCI standard. This has been pointed out to you, that they have adopted it, numerous times but you choose to selectively ignore it.

ABYC E-11 does include an ELCI/RCD device. That said 98% of boats in this country are built and wired for the old standard and our docks are "generally" (IMHO) very poorly maintained and the wiring can be suspect. Dropped AC grounds on the docks are not at all uncommon. I alerted one local marina of a dropped ground last June and as of early August it was still not fixed.

The ABYC PTC has been over and over the ELCI/RCD AC/DC grounding issue and, based on evidence, it was decided to keep the on-board AC/DC grounding connection AND use an RCD/ELCI device. I recently had conversations with both Ed Sherman and John Adey, of the ABYC, about this specific subject. For now the standard includes both an ELCI/RCD and AC/DC grounding on-board.

The ABYC standards are written for safety first and not around what will or will not corrode your boat faster as the first priority. Anyone plugging into dock power without an isolation transformer or at the least a galvanic isolator is, well, taking a HUGE risk in this country.

The PTC has made the decision to keep the AC/DC grounding and add the ELCI/RCD based on case evidence of failures of RCD/ELCI devices to fully protect as they are intended to. They have decided to keep the AC/DC grounding tie, for now, as redundancy to the ELCI/RCD. As we know all things electronic on boats can and do fail.
Maine Sail. I have never denied that ABYC now have included whole boat residual current devices in their latest spec. Great and only about 10 years too late.

What I have argues is that the DC AC connection is fundamentally flawed logic and in my mind contributes greatly to the corrosion issues that seem much more prevalent in the US. ( as a direct result of this interconnection)

Again my understanding for the reason for the interconnect was not to provide an alternative ground out of the boat but to include DC devices that could become AC hot and hence with the interconnect be included in the AC earth protective path. This is what herr Calder referred to.

The secondary claim of a alternative path to ground is open to challenge. I'm not aware that US boats as standard practice install DC ground plates , so are ABYC relying on engine/prop shaft etc.

Think what happens if you have a medium resistance path to sea water. Then add an AC ground disconnect fault and then add a AC onboard fault Significant current could flow continuously, not tripping the breaker and potentially causing death.

The fact is the the interconnect causes as many safety issues as it seeks to prevent, it's just a matter of hypothesising different fault scenarios. It was originally specified because in the absence of Residual Protection devices it was about all you could do. It's a very imperfect solution. It has directly led to galvanic isolators which is a further chewing gum solution to the problems caused by the ACDC interconnect.

European practice is a pointer to how it should be done, arguably because we have to deal with a more lethal arrangement to begin with. Marinas will have RCD on the supply pillars, further RCD often on intermediate supply's and the boat itself will have an RCD, all mandatory code and in place since the 80s , 30ma RCD or integrated with an overload RCBOs are commonly available everywhere at about $50 dollars a pop. The devices have proven to be very reliable and a life saver.

Fit one today. ( and consider that ACDC interconnect carefully )

Dave
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Old 16-02-2012, 19:33   #44
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Re: A/C Wiring Short ?

Thanks for the update Gord, I was looking at the 2007 NEC. I will be following the new dock construction at the Santa Cruz harbor with interest to see if they follow the new code. If they do, there is going to be full employment for marine electricians for a while, because I have measured over 200 ma ground faults on a number of boats.
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