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Old 19-02-2015, 02:28   #196
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Re: Reverse Polarity

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Originally Posted by FlyingCloud1937 View Post

In the US we protect against the lowest denominator, which is children, and the elderly. Why? to save human life.

And yet you don't install RCD's as standard? (Well, you do now, half a century after Europe...)



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Old 19-02-2015, 02:30   #197
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Re: Reverse Polarity

If I could only quote one death, and that was of your child or loved one would it matter?

Most RCD believers always trot out, that you need not worry about the ac/DC bond when an RCD is employed...do you believe that?

Lloyd

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Originally Posted by svlamorocha View Post
Can you quote a statistic of deaths to electrocution by earth fault where a 30mA did not trip?

Corrosion is another problem for which there are other solutions, and it it is not caused by AC anyway.


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Old 19-02-2015, 03:03   #198
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Re: Reverse Polarity

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Originally Posted by K_V_B View Post
Why not? There is no reason why you cannot earth the boat as well. That way you are not dependent on the shore power to be properly earthed.
So you are saying that as soon as you haul the boat, you drive a ground, and connect it to the bonding system? Before for you plug into the shore power in the yard.

I'll bet not!

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An RCD wouild already have trippped and disconnected the power even before anyone touched the prop.
An RCD will only trip once it meets the fault requirement, 22.3 mA. It is floating until then, So a ground fault of 18 mA, which is above the 6 mA US requirement for UL fault tolerance. Is just waiting to happen.

Now in the real world, it may not cause an injury, but if it does then the death/injury is all YOURS, not your insurance companies.

If it turns out to be your loved one can you live with that?

Lloyd
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Old 19-02-2015, 03:35   #199
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Re: Reverse Polarity

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Originally Posted by FlyingCloud1937 View Post
So you are saying that as soon as you haul the boat, you drive a ground, and connect it to the bonding system? Before for you plug into the shore power in the yard.

I'll bet not!
I've gotten pretty convinced by now that I should. But the last time we hauled we didn't connect up shore power at all. One of the things we worked on was the AC system. (Installed a new shore power cord, and an RCD...)


Quote:
An RCD will only trip once it meets the fault requirement, 22.3 mA. It is floating until then, So a ground fault of 18 mA, which is above the 6 mA US requirement for UL fault tolerance. Is just waiting to happen.

Now in the real world, it may not cause an injury, but if it does then the death/injury is all YOURS, not your insurance companies.

If it turns out to be your loved one can you live with that?
So you are saying that a safety device is only useful if it manages to save everyone? That is a very odd reasoning.

Could you live with the death of a loved one if a RCD you couldn't be bothered to install would have prevented it?
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Old 19-02-2015, 03:45   #200
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Re: Reverse Polarity

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Originally Posted by FlyingCloud1937 View Post
If I could only quote one death, and that was of your child or loved one would it matter?
I am afraid I do not understand your point. As consultants say, let's get an answer that goes in the right direction to start!

First let me ask you: Do you understand that the worry about one baby that could be killed if a 30mA RCD does not trip before people get killed (proved unfounded by five decades of real-world experince of babies sticking things in outlets, etc) ends up being a reason for not installing whole house/boat RCDs which kills MANY babies and older people EVERY year?





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Old 19-02-2015, 04:23   #201
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Re: Reverse Polarity

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Originally Posted by FlyingCloud1937 View Post
Most RCD believers always trot out, that you need not worry about the ac/DC bond when an RCD is employed...do you believe that?
I am religious (Christian in fact) but do not mix religion and electricity, so I can explain my position.

When you have a proper whole-boat RCD the bond between ac green and metal on the boat (ie DC negative) only makes a difference if there is a hot AC wire touching the engine or a DC wire and the RCD is not working well. Then the AC-DC bond provides two benefits: a) starts the RCD mechanism when the wire touches the engine without waiting for someone to touch the hot engine; and b) if the 30mA RCD is completely defective (as opposed to slow) it increases the fault current to give a (chance) of getting the 15A normal circuit breaker to trip.

In summary, we are talking about helping with a fraction of 1 per cent of the cases where the engine gets hot with AC, net of the fact that instead of just the engine we "heat up" the frame of all the AC appliances.

For comparison, an RCD helps in 99% of those cases. Is this enough to persuade or do I have to quote the Bible like Holt?

Yes, I do bond AC and DC in my own boat. I just do not let the bonded metal (basically engine) touch the water by inserting isolation in the shaft coupling. I deal with lighting separately by tying the mast to the keel. I confess I do not know what will I do if one day I switch to the dark world of multihulls!

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Old 19-02-2015, 05:39   #202
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Re: Reverse Polarity

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Originally Posted by K_V_B View Post
I don't find this that controversial. It's good practice in my opinion. It does create a problem with ground loops that can cause galvanic corrosion, but there are easy fixes for that.
It's controversial when there is an isolation transformer installed.

I personally question it on pure shorepower also...
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Old 19-02-2015, 06:10   #203
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Re: Reverse Polarity

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Originally Posted by DotDun View Post
It's controversial when there is an isolation transformer installed.

I personally question it on pure shorepower also...
The author of this article argues you should bond AC and DC ground together:

SmartGauge Electronics - To bond or not to bond - Hulls and electrical earthing

Don't confuse this with tying AC neutral and Ground together.
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Old 19-02-2015, 07:20   #204
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Re: Reverse Polarity

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Originally Posted by K_V_B View Post
The author of this article argues you should bond AC and DC ground together:

SmartGauge Electronics - To bond or not to bond - Hulls and electrical earthing

Don't confuse this with tying AC neutral and Ground together.
No confusion, I understand the difference between AC neutral/safety ground bond and the completely different topic of earthing such ground. ("earthing" in vessel context = AC safety ground/DC negative/engine/thru hull bonding)

The article you referenced continual talks about the case of a metal hull boat and single insulated appliances.

I believe that in a GRP vessel, the chance of an AC live wire chafing against a metal engine block/metal thru hull/ground plate/rail AND a human touching such AND the RCD failing is so remote it's to the point of fantasy. Hence, why earth the AC safety ground?
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Old 20-02-2015, 12:03   #205
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Re: Reverse Polarity

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Originally Posted by mestrezat View Post
I just got into another marina and my boat is registering "reverse polarity" on my panel. My connectors have been fine all the way up and down the Melacca Straits.
I took apart the connector plug and reversed the wires--positive went to negative and the negative wire to the positive position and still I get the same reading.
I put my volt tester into the plug and got 240 volts when I touched the positive and negative wires. I got 240 volts when I touched the positive and ground wires. I got nothing when I tried the ground wire to the negative plug. Not sure if this is correct as to the power in the lines. I've checked all my connections and they appear to be fine. The marina's position is that it has to be me since everyone else is fine. The electrician they sent down tried numerous power posts in the marina and all came back the same as mine but he thinks there is a problem with the ground and positive wires showing volts.
Any thoughts as to what to try next? I'm going to be here for a couple of weeks and I'm sure my neighbors won't like hearing my generator ever other day.
Have not read all the highly charged pages but if it is only at one specific marina in Asia... Odds are that they Micky moused the shore side connection by combining more than one leg of a different voltage supply to give you 240v.
Had the same happen to me in the Philippines and once confirmed as to why?, I temporarily disconnected the Reverse Polarity alarm and main breaker trip to get power to AC panel.
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Old 20-02-2015, 12:21   #206
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Re: Reverse Polarity

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Originally Posted by Pelagic View Post
.............. I temporarily disconnected the Reverse Polarity alarm and main breaker trip to get power to AC panel.
Not something I would recommend or even admit to. These are important safety devices and are there for a purpose - to protect you from a potential life threatening condition and to protect your boat from an electrical overload and fire.

If a marina can't provide the power you need safely, it's time to move to another marina or say no thanks to the power and provide your own.
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Old 20-02-2015, 12:53   #207
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Re: Reverse Polarity

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Have not read all the highly charged pages
Ha! Is that an electrical joke?

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Old 20-02-2015, 16:12   #208
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Re: Reverse Polarity

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Ha! Is that an electrical joke?

It sparked your interest!
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Old 21-02-2015, 08:56   #209
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Re: Reverse Polarity

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Originally Posted by rwidman View Post
Not something I would recommend or even admit to. These are important safety devices and are there for a purpose - to protect you from a potential life threatening condition and to protect your boat from an electrical overload and fire.

If a marina can't provide the power you need safely, it's time to move to another marina or say no thanks to the power and provide your own.
In a perfect world I would totally agree. But in Asia, Marinas and yacht repair facilities operate on shoe string budgets and are few and far between
You do what you have to do to 'get er done'
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