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Old 13-04-2011, 11:07   #16
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Re: Shore Power Question

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Originally Posted by sailvayu View Post
Running an extension cord is a hazard. All appliances need to have a ground in the boat. The appliance must be connected to the boats earth ground.
Agreed

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Originally Posted by sailvayu View Post
Please consult an expert on this, the advice you are getting here is wrong for the most part. AC can be very dangerous around water. Just because some have gotten away with it does not make it safe
Oh Doug and I have both said do it properly as you and Dave have? Nick also highlighting issues, looks like the majority of advice is correct to me.

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Old 13-04-2011, 11:51   #17
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Originally Posted by sailvayu
Dave the difference between the automotive chargers and marine is the way the windings are isolated from each other. Marine chargers the ]high and low voltage circuits are isolated from each other. They are also required to have a fault current path to ground. Automotive chargers and inverters may have the fault path to ground and neutral connected together, this can cause a current flow to your boats ground or worse to you if you touch the case. This is why I keep saying use only marine approved chargers and inverters. Also why using an extension cord is so dangerous. ABYC writes this stuff not to raise the cost of products but because people have died.
Most modern car chargers are isolated just like supposed marine ones. The old auto traffo ones are rate enough now.

But to examine your statements.

"Automotive chargers and inverters may have the fault path to ground and neutral connected together, this can cause a current flow to your boats ground or worse to you if you touch the case"

Firstly there is no such thing as a " fault path" to neutral. Neutral is by definition a proper return path. Neutral is never connected to ground in an appliance ( except where rf suppression may be present)

" fault" paths to neutral" to use your terminology are short circuits and hence why you have fuses and breakers etc.

A fault to ground whether in a " car" charger or a so called marine charger only causes temporary current flow until a RCD or a fuse fails. In either case the same fault causing the ground to go hot is handed by a fuse blow ( that is the purpose of a ground or more correctly called a protective ground. )

A double insulated automotive charger is as safe as a so called marine unit.

What I find funny is that people simply don't understand the first principles.

An extension lead that includes it's own RCD , is as safe or unsafe as a shore power lead.

But I know this isn't ABYC as they want the ground wire connected to DC negative. A situation that causes more trouble then it's worth and protection by RCD and no connection ( the European way) is a better compromise.
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Old 13-04-2011, 11:59   #18
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Also why using an extension cord is so dangerous. ABYC writes this stuff not to raise the cost of products but because people have died.
A lot of international standards such as ISO do not agree with aspects of ABYC. For example while whole boat RCD has only recently been discovered by the ABYC yet it's been mandated by ISO for years. ( and these are 230vac) the ABYC specifications on invertors and chargers miss the point as they are stipulated in a non-RCD world.

It's important not to let country specific standards and actual understanding of first principles get confused. Just because a standards organisation says it's safe or unsafe needs to be evaluated in relation to the particular installation and exactly what is bring done.


For example i would argue that's RCD protected extension lead is safer for all concerned that a non RCD protected shore power installation. Yet ABYC has signed off on the latter whereas ISO mandates the former. !!

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Old 13-04-2011, 12:13   #19
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Re: Shore Power Question

This is why I hate even talking electrical issues here.
You say "Most" automotive chargers but how does the average boat know the difference? At least they know for sure with a marine charger.

"A fault to ground whether in a " car" charger or a so called marine charger only causes temporary current flow until a RCD or a fuse fails. In either case the same fault causing the ground to go hot is handed by a fuse blow ( that is the purpose of a ground or more correctly called a protective ground. )"

So if the fault to ground is going through my body I have to wait till the fuse blows, hope my heart can wait that long

"An extension lead that includes it's own RCD , is as safe or unsafe as a shore power lead."
This assumes that the cord has a RCD the OP was talking about plugging a 15 AMP cord into a 30 AMP fixture if I read it right. This also does not provide a boat ground

It bothers me that people on this forum tell others to do unsafe things. Risk your life but not that of others. I am done and I swear this will be the last electrical post I ever do here there are simply more people advising dangerous things than there are those advising the correct things. They argue for doing the unsafe for whatever reason. Like I said the ABYC recommendations are clear and written for good reason.
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Old 13-04-2011, 13:24   #20
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Re: Shore Power Question

Salivayu, don't worry so much. Look at it this way: ABYC standards are only one of a set of norms and rules and, in some respect, appear to be... dated?

Let me address your concerns from the above post.

"How the customer is to know the safe charger?" - easy, they need to look for a 'double insulation' symbol on the case. This symbol looks like a square within a square and tells them, that a given charger/tool/etc. was designed to a certain protection standard. Such devices are very common nowadays. They have output fully isolated from input and also a totally isolated case. By standard, they do not even require a protective earth connection. Would be good if the device was designed to a proper IPX rating too, to account for a high humidity environment.

Later, it appears to me that you confuse two fault modes: an overcurrent and a 'fault to protective earth'. First is dealt with by a fuse, second is dealt with by a Differential Disconnect (which, for some strange reason is known here as RCD). Modern standards call for both fuses and DD to be installed. Often they are combined in a single unit, but that is a different story.

You wrote "So if the fault to ground is going through my body I have to wait till the fuse blows, hope my heart can wait that long". This is incorrect. This particular fault mode is a job for a DD, which will disconnect in milliseconds. IF the DD is installed on a boat, even protective ground connection to shore is not required for this protection to work, although may be a good idea for other reasons.

Rather than quitting with 'electrical posts' let's discuss possible fault modes and see what protection will work and what will not.
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Old 13-04-2011, 17:08   #21
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Re: Shore Power Question

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It bothers me that people on this forum tell others to do unsafe things. Risk your life but not that of others. I am done and I swear this will be the last electrical post I ever do here there are simply more people advising dangerous things than there are those advising the correct things. They argue for doing the unsafe for whatever reason. Like I said the ABYC recommendations are clear and written for good reason.
Blind faith without understanding is a dangerous thing, ABYC is not a gospel.


Quote:
Rather than quitting with 'electrical posts' let's discuss possible fault modes and see what protection will work and what will not.
mrm, youre a beacon of hope in the midst of a fog of confusion. BTW RCD stands for Residual Current Device, its what they are called in Europe. ( or sometime a RCDD)

Quote:
You say "Most" automotive chargers but how does the average boat know the difference? At least they know for sure with a marine charger.
sailvayu, thats fine for a US manufactured charger, however, due to the differnce in standards theres no worldwide standard situation, you have to undertstand the issues, problems and resolutions.

I put up two posts, becuase I get exasperated when people just trot out so called good or "standard" practice without any real underlying knowledge. Equally people "invent" fault modes and dangers that rarely if ever exist. No AC protection system is perfect , all have fault modes that are lethal, differnt standards bodies focus on different things. IN the UK you cant have a mains socket inside a bathroom, end of story, in Germany ive seen them within a foot of a bathroom sink, all are nominal 230Vac, both are heavily standardised and regulated industries, go figure.

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Old 13-04-2011, 17:33   #22
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Re: Shore Power Question

The original poster asked if it is a good idea to run an extension cord into the boat and run appliances off that. The plan and simple common sense answer is NO it is not a good idea. Sure you can make it safe but the bottom line is in most cases it is not.

Going off on tangents about US, Eruo standards, battery chargers and on and on is pointless. I for one am not smarter than the combined technical staff of ABYC so yes I fall back on their advice. I do not agree with everything they say yet I am not going to advice novices to not follow the standards because I "think" I might know better.

So back to the topic NO it is not a good idea to just run an extension cord into the boat

End of discussion. (at least for me)
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Old 13-04-2011, 17:36   #23
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Re: Shore Power Question

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So back to the topic NO it is not a good idea to just run an extension cord into the boat
can you give me some reasonable electrical reasons why that is the case


My view is a GFCI ( as they are known in the US) extension cord is safer that a shore power system without a GFCI. so my advice is that yes if you want to use an extension cable then use a GFCI protected one.

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Old 14-04-2011, 02:49   #24
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Re: Shore Power Question

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Originally Posted by sailvayu View Post
The original poster asked if it is a good idea to run an extension cord into the boat and run appliances off that. The plan and simple common sense answer is NO it is not a good idea. Sure you can make it safe but the bottom line is in most cases it is not.

[...]

So back to the topic NO it is not a good idea to just run an extension cord into the boat

End of discussion. (at least for me)
Fire away!
OK, I see now where you are coming from. And I will agree that considering the worst case scenario your stand is correct. I can see at least three different cases here:

  1. an extension cord (with or without protective earth) is used to connect *a boat* to shore power and appliances inside a boat are run off boat's sockets. If the boat is equipped with its own fuses and Differential Disconnect I can think of no fault mode (other than faults of protection devices) that would present a hazard to humans in this case.
  2. an extension cord *equipped with its own DD and overcurrent protection* is run from shore directly to boat (bypassing boat's circuits) and appliances are run directly off that power cord. I see this as analogous to point 1.
  3. an ordinary extension cord (basically, a bunch of wires) is run from shore power directly to appliances. This can be dangerous. I see at least three possible fault modes:
  • shore power overcurrent protection may have higher current rating than maximum for the extension cord used. Fire hazard. Electrocution hazard from exposed wiring if insulation melts.
  • shore power may or may not have Differential Disconnect protection, or it may be old and not operational, or it may be run off a different phase a boat is connected to (if connected). Electrocution hazard.
  • shore power protective earth connector may have a substantial potential above earth. Shock hazard.

So I guess you want to say "If you do not know/understand what you are doing, do it safely" and I agree with it. I would only add "don't follow safety rules blindly, try to understand them".

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Old 14-04-2011, 18:22   #25
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Re: Shore Power Question

<rant>

ABYC just gives some recommendations... these are not rules or code at all.

I agree with other posters that their (ABYC) guidelines are dated, some even obsolete, and their attempts to polish it up with acknowledging the existence of GFCI (which is actually a literal translation of how it used to be called in Holland) are painfully incomplete, showing a lack of interest in the whole issue, which greatly lowers their "authority" in this area of expertise.

It reminds me of Tesla calling out that AC is the way to go while the US was building DC power grids and ignoring him. If Tesla wouldn't have build the AC generating power plant at Niagara Falls, the US might have had DC still today.

So it actually is needed to look further than ones own nations borders, and in the case of AC power aboard our yachts, one will be better off when looking at European codes and practices, and even European equipment (Victron, MasterVolt, DIN rails etc. instead of Xantrax, Blue Sea Systems etc.)

Example: I am not convinced that any law or rule in the USA states that AC protective ground must be connected to DC negative. I think it's an obsolete guideline from ABYC only.

</rant>

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Old 12-05-2011, 22:27   #26
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Re: Shore Power Question

ABYC E11 which was meant to come in 2 years ago but got postponed to this year was for every new boat to have a special GFCI fitted to the main shorepower line, this was due to a few accidents caused by boats with ground faults creating stray current in the water, only a tiny amount of current in fresh water can cause people swimming close to the boat to drown.

Proper wiring is a must on a shorepower connection for everyones safety!
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Old 12-05-2011, 22:56   #27
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Re: Shore Power Question

Many years ago, when I spent most of my time in lakes, I took a Fall holiday in salt water.The first night I launched and stayed in a marina with shore power. I ran an extention cord to a heater for the night. Next morning I was ready to go, forgot about the heater. As I left the dock there was a flash as the cord parted. The dark spot in the gelcoat was there when I sold her. Dangerous? who knows proper? definitely not. And definitely not wise.
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