Earth/Hull bonding

[GUMPY]

Of course it needs an earth. That is through the landline. It doesn't need to be the hull

 

 

What you have said is the same as saying thet you would disconect the earth from the micowave case as in an earlier example.

Cant you see that the hull of the boat is the same as the case of any electrical appliance that is not double insulated.

[blackrose]

What you have said is the same as saying thet you would disconect the earth from the micowave case as in an earlier example.

Cant you see that the hull of the boat is the same as the case of any electrical appliance that is not double insulated.

 

I need no more convincing.

Edited November 17, 2006 by blackrose

[miles beyond]

What you have said is the same as saying thet you would disconect the earth from the micowave case as in an earlier example.

Cant you see that the hull of the boat is the same as the case of any electrical appliance that is not double insulated.

 

Yes I can and my last post wasn't properly explained. Sorry.

 

If you believe that there is the chance that your mains can develop a fault and leak to the hull without tripping the boat RCD then OK. Where you have earthed appliances all returning through the 3 core cable earth to the earth provided by the on shore connection, and that cable is separated from the hull by not onlt the cable insulation, but the boat insulation and often woodwork too, I personally feel this is such an unlikely event that I can't worry about it. And I simply do not accept this drowning rubbish. You do not see dead mammals floating past ona regular basis. I haven't seen one at all where I am at present in the 1.5 years I've been here. So I have no desire to bond my earth to the hull and generate a whole new set of galvanic corrosion problems and I am by no means alone in this view.

[bottle]

There is a chance that galvanic corrosion happens, there is a chance that a hull could become 'live', there is a chance that you touch the hull and an 'earth'.

 

There is a chance that I could win the lottery (actually not because I don't buy a ticket), there is a chance that my Premium Bond will come up.

 

There is a chance of being run over by a bus etc.

 

Now all of things happen so, there is a chance that a non-bonded boat could kill someone, now if you wish to take that chance that is entirely up to 'you'.

 

I just hope 'you' are well insured.

[miles beyond]

There is a chance that galvanic corrosion happens, there is a chance that a hull could become 'live', there is a chance that you touch the hull and an 'earth'.

 

There is a chance that I could win the lottery (actually not because I don't buy a ticket), there is a chance that my Premium Bond will come up.

 

There is a chance of being run over by a bus etc.

 

Now all of things happen so, there is a chance that a non-bonded boat could kill someone, now if you wish to take that chance that is entirely up to 'you'.

 

I just hope 'you' are well insured.

Indeed. Life is full of chances. Risks need to be calculated and that calculation is frequently subjective - it has to be. Your bonded earth-hulled boat may squash the life out of somebody who slips and falls into a lock. Its prop could maim or kill someone. Etc etc. All of those things happen too. Perhaps you should move into a padded cell and never go out. And stop eating in case the food is infected with deadly e-coli.

 

I'm going for a pint personally. I wonder if I'll get run over on the way, struck by lightning, or acquire salmonella as the landlord has forgotten to clean the pipes properly. I'll take the risk.

[Guest]

There is a chance that galvanic corrosion happens, there is a chance that a hull could become 'live', there is a chance that you touch the hull and an 'earth'.

 

There is a chance that I could win the lottery (actually not because I don't buy a ticket), there is a chance that my Premium Bond will come up.

 

There is a chance of being run over by a bus etc.

 

Now all of things happen so, there is a chance that a non-bonded boat could kill someone, now if you wish to take that chance that is entirely up to 'you'.

 

I just hope 'you' are well insured.

And have a very good solicitor. Like any other walk of life, one has a duty of care to others.

[GUMPY]

Yes I can and my last post wasn't properly explained. Sorry.

 

If you believe that there is the chance that your mains can develop a fault and leak to the hull without tripping the boat RCD then OK. Where you have earthed appliances all returning through the 3 core cable earth to the earth provided by the on shore connection, and that cable is separated from the hull by not onlt the cable insulation, but the boat insulation and often woodwork too, I personally feel this is such an unlikely event that I can't worry about it. And I simply do not accept this drowning rubbish. You do not see dead mammals floating past ona regular basis. I haven't seen one at all where I am at present in the 1.5 years I've been here. So I have no desire to bond my earth to the hull and generate a whole new set of galvanic corrosion problems and I am by no means alone in this view.

 

Any 230v installation can develop a fault it doesn't have to be in an appliance It could be where a cable passes through a steel bulkhead or wall.

How often do you have your boat electrics tested?

Are you sure there has been no breakdown in the insulation of the cable?

 

You can mitigate the effects of galvanic corrosion easily by fitting an isolation transformer.

You can not mitigate the effects of a live hull giving someone a shock or killing them.

[smileypete]

Hi

 

I'll add my view...

 

I do think that hull earth bonding is A Good Thing.

 

But what causes electrocution is not just a lack of hull earth bonding, but a lack of RCD protection.

 

A look at the electrocution fatalities on boats in the US shows that it is not just bonding problems, but badly wired and faulty shorelines.

 

You can have perfect bonding on every boat, but it relies totally on a working shoreline earth.

 

I do think that a damaged or faulty shoreline is far more likely than an RCD failing to operate.

 

In order for an RCD allow a fatality, you need:

 

1) A faulty RCD

2) A boat with 'partial shorts' from live to earth which miraculously leak less than 30 milliamps, PLUS swimmers to come and hold onto the bare hull with their hands!

 

In order for a hull earth bond to allow a fatality you need:

 

1) A faulty or damaged shoreline

2) A faulty connection between hull and earth.

 

Which is more likely?

 

I'm not saying that hull earth bonding isn't needed, but that to focus exclusively on it is missing out on the wider picture.

 

I do think it's still worth having and RCD on the boat too, as it gives an even higher overall level of protection, and it can also be used with a generator or inverter.

 

cheers,

Pete.

[Guest]

Hi

 

I'll add my view...

 

I do think that hull earth bonding is A Good Thing.

 

But what causes electrocution is not just a lack of hull earth bonding, but a lack of RCD protection.

 

A look at the electrocution fatalities on boats in the US shows that it is not just bonding problems, but badly wired and faulty shorelines.

 

You can have perfect bonding on every boat, but it relies totally on a working shoreline earth.

 

I do think that a damaged or faulty shoreline is far more likely than an RCD failing to operate.

 

In order for an RCD allow a fatality, you need:

 

1) A faulty RCD

2) A boat with 'partial shorts' from live to earth which miraculously leak less than 30 milliamps, PLUS swimmers to come and hold onto the bare hull with their hands!

 

In order for a hull earth bond to allow a fatality you need:

 

1) A faulty or damaged shoreline

2) A faulty connection between hull and earth.

 

Which is more likely?

 

I'm not saying that hull earth bonding isn't needed, but that to focus exclusively on it is missing out on the wider picture.

 

I do think it's still worth having and RCD on the boat too, as it gives an even higher overall level of protection, and it can also be used with a generator or inverter.

 

cheers,

Pete.

I think an RCD is essential when you are playing with 240V supply in a metal tank, which is floating in mucky water. I agree that it is essential that the whole system is efficient, of which the earth bond is a part.

[Big COL]

Hi all

 

I have been following this thread and have read Gibbo's web pages. As regards swimming in a marina while the voltage is raised From zero to whatever before it trips the shoreline RCD I will do this, no problem whats so ever. Providing that the shoreline RCD is in perfect working order.

Lets suppose without anyone being in the water and you managed to raise the voltage to 100v in the water, and the dropped the probes from a multi meter into the water what voltage or amperage would you expect to read on the meter?

Cock strutting and flaunting degrees mean nothing to the guy on the ground. I have seen thousands of so called experts flounder once you put a spanner or screwdriver in their hand. Give me people like Snibble

shit in the fingernails type of guy every time, he earns a living by what he knows and can do.

Personal dog fights do not help the members of any forum, amusing as they may be to those that can follow and understand, they mean nothing to the majority and only confuse a lot of readers.

PM me as to where I am going swimming, bring plenty of beer as I am sure there will be loads of people after a free beer.

[blackrose]

Hi all

 

I have been following this thread and have read Gibbo's web pages. As regards swimming in a marina while the voltage is raised From zero to whatever before it trips the shoreline RCD I will do this, no problem whats so ever. Providing that the shoreline RCD is in perfect working order.

Lets suppose without anyone being in the water and you managed to raise the voltage to 100v in the water, and the dropped the probes from a multi meter into the water what voltage or amperage would you expect to read on the meter?

Cock strutting and flaunting degrees mean nothing to the guy on the ground. I have seen thousands of so called experts flounder once you put a spanner or screwdriver in their hand. Give me people like Snibble

shit in the fingernails type of guy every time, he earns a living by what he knows and can do.

Personal dog fights do not help the members of any forum, amusing as they may be to those that can follow and understand, they mean nothing to the majority and only confuse a lot of readers.

PM me as to where I am going swimming, bring plenty of beer as I am sure there will be loads of people after a free beer.

 

I'll bring me camera! I think you might have the wrong idea about Gibbo. From what I gather he knows how to handle a screwdriver & his fingernails are in a terrible state.

[ChrisPy]

And have a very good solicitor. Like any other walk of life, one has a duty of care to others.

Catweasel, you have the gift of producing very succinct replies.

 

Yes, I suggest that if Milesbeyond has a boat it should carry a large health warning sign ..............

[Gibbo]

Lets suppose without anyone being in the water and you managed to raise the voltage to 100v in the water, and the dropped the probes from a multi meter into the water what voltage or amperage would you expect to read on the meter?

 

It depends exactly where you put the probes. You would get 100 volts right at the side of the hull, decreasing to 0 volts by the time you got to the bottom or edge of the canal. A voltage gradient.

 

Let's assume that's over a distance of 10 feet.

 

A 6 foot long body (a swimmer?) pointing between these two would therefore have 6/10ths of this voltage gradient along the length of his body, 60 volts.

 

Note that this is rough and ready as it neglects the fact that the lower resistance through the body (assuming fresh water not salt water) would reduce the actual voltage along it's length. The extent of this depends upon the conductivity of the water.

 

But also note that if the body has a lower resistance that the water then the bulk of the current will pass through the body not through the surrounding water.

 

Trust me, you do *not* want 60 volts across your body when trying to swim.

 

American GFCIs (their term for an RCD) trip at 5mA. This figure was arrived after experiments in which volunteers were immersed in water and an increasing current passed through their body until they could no longer control their muscles. i.e. could no longer swim effectively. 5mA was deemed to be the safe limit. This is easily verified with a quick google search.

 

Gibbo

[ChrisPy]

It depends exactly where you put the probes. You would get 100 volts right at the side of the hull, decreasing to 0 volts by the time you got to the bottom or edge of the canal. A voltage gradient.

 

yes, voltage gradients are real fun. the milliamps tend to run downhill so easily. PLEASE DON'T TRY IT AT HOME OR IN THE CANAL !!

 

(we want to keep the membership numbers healthy)

[Gibbo]

Hi all

 

I have been following this thread and have read Gibbo's web pages. As regards swimming in a marina while the voltage is raised From zero to whatever before it trips the shoreline RCD I will do this, no problem whats so ever. Providing that the shoreline RCD is in perfect working order.

 

Will you do it if you know the RCD is not in perfect working order?

 

Will you do it if there is no RCD on the shoreline? (they are not mandatory).

 

Will you do it if you realise that *much* less than 30mA will more than likely paralyse a swimmer? (look it up on the net, it's well documented).

 

Bonding the earth to the hull will prevent the danger in all the above cases.

 

Gibbo

[Gibbo]

I'm getting really confused by this thread.

 

No matter what evidence is produced, be that technical explanations of how someone could be electrocuted, (explanations that no one can dispute), or statistical evidence that people have died as a result of boats not having the earth bonded to the hull, there are still some people who think it is not necessary to bond the earth to the hull. Indeed some people seem to refuse to do it no matter what.

 

The technical arguments are clear - yet I hear "but it's unlikely so I won't bond"

 

The documented cases of death are numerous yet I hear "well he was only a county sherrif". Even though the county coroner (a qualified medical professional) confirmed electric shock and they engaged a qualified electrical engineer who found the fault that caused the electrocution. And several other witnesses all confirmed feeling tingling sensations in the water and having to reteat.

 

Yet I still hear "I don't want to bond it"

 

What have I missed?

 

Gibbo

 

PS. Or as my mate (an EE) just put it after having read this thread........

 

"How can anyone be so stupid with only one head?"

Edited November 18, 2006 by Gibbo

[tomsk]

I have two heads, and they both have headaches .

 

Question; Was electricity discovered just to propagate 'discussions' of a heated nature between experts in hairsplitting?.... Discuss...

Edited November 18, 2006 by tomsk

[blackrose]

Indeed some people seem to refuse to do it no matter what.

 

I think that's it - my neighbour said he won't do it because he doesn't want to intoduce galvanic problems. Yet when I reminded him that his iron hull was a more noble metal than all the steel boats around him, so that at least in his case this was not a valid argument, he just grunted.

[Gibbo]

Question; Was electricity discovered just to propagate 'discussions' of a heated nature between experts in hairsplitting?.... Discuss...

 

ELECTRONICS ENGINEER is an anagram of EGOCENTRIC SNEER LINE

 

Gibbo

Edited November 18, 2006 by Gibbo

[Big COL]

Will you do it if you know the RCD is not in perfect working order?

 

Will you do it if there is no RCD on the shoreline? (they are not mandatory).

 

Will you do it if you realise that *much* less than 30mA will more than likely paralyse a swimmer? (look it up on the net, it's well documented).

 

Bonding the earth to the hull will prevent the danger in all the above cases.

 

Gibbo

 

Hi Gibbo

 

It's your challenge I was prepared to do, you are now moving the goalpost I didn't say I disagreed with your reasoning. Due to your convincing argument, I need to re-evaluate just how the mains system is configured on my boat. At the time of installation and because an isolation transformer is being used the shore line earth was not used.

[Collectors]

Quite a good bit of reading at this link http://www.ybw.com/ym/any_questions/200411...021ymanyqs.html & even mentions the use of students to test the theory. (Like it)

Its Just a view on the US & UK ways of doing things. And still has a bit of controversy on which way things should be done. Still a good read for different ways of using power..

 

Chris.

[blackrose]

My 12v earth link comes off the engine block and is connected to the main 240v earth stud. I'm going to separate them & have a dedicated 12v earth stud as recommended, but does it have to be welded on to the hull or is a stud held in place by nuts + locknut either side good enough? (My counter overhangs the swim by about 2 inches so I could drill through there.) I assume nylock nuts would not be a good idea?

Edited November 18, 2006 by blackrose

[John Orentas]

Can't quite see why you should need a 12 volt earth connection but I am confused about lot's of things now, the normal is simply to connect engine block to battery bank for the starter motor.

 

Not a good idea to drill through your hull, can't you find some framing, an internal bulkhead or a coaming to drill into. The best way to bond such things is usually to use stainless steel or copper star washers.

Edited November 18, 2006 by John Orentas

[chris w]

Collectors

 

Quite a good bit of reading at this link http://www.ybw.com/ym/any_questions/200411...021ymanyqs.html & even mentions the use of students to test the theory. (Like it)

Interesting link. He does though have an error in his calculations. He states that the minimum resistance for a reverse polarity device needs to be ABOVE 8000 ohms in the UK or it will trip the RCD.

 

He means it needs to be BELOW 8000 ohms.

 

Otherwise it won't trip the RCD if live and neutral are reversed. If this situation obtains (ie: L & N) reversed there would now be 240v on the former neutral and the former live would now be earthed). You need at least 30mA to trip the RCD. I would use a 5000 ohm resistor (this would be about 50mA) to ensure definite tripping.

 

5000 ohms won't trip the RCD under correct polarity conditions (which is the situation you want) because there is then only a couple of volts between neutral and earth to drive current through the 5000 ohm resistor which is way below that needed to trip the RCD.

 

Chris

Edited November 18, 2006 by chris w

[Chris Lingwood]

Good lord some people are ignorant. I wouldn't normally say anything but you don't piss around with mains voltages! I just hope you don't hurt yourself or worse still someone else!

 

Are some of you people honestly telling me that you want to endanger peoples lives just to avoid a little bit of metal evaporating off your boat. Christ!