Earth/Hull bonding

[Collectors]

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?

 

Nylocks shouldn’t create any problems as it’s the connecting lug on the cable, washers & bolt that make the connection to the hull & not the nut it self. Just make sure the hull has nice clean metal where you connect to on both sides of the hole.

Maybe worth finding an internal rib of steel to do this on.

 

 

Chris.

[Gibbo]

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.

 

 

If the boat only has a DC system it makes no difference whether it is bonded to the hull or not.

 

However if it not bonded, an accidental bond from positive to hull (maybe just a partial one) then leaves enormous scope for stray current erosion.

 

If there is an AC system on board then the DC system negative needs to be bonded to the AC system earth. The reason being to ensure correct operation of fuses, circuit breakers and RCDs in the event of a fault between 230 volts and the DC system otherwise you may end up with the DC system at 230 volts.

 

Gibbo

[Gibbo]

Good lord some people are ignorant.

 

It's not just ignorance. It's arrogance, selfishness and stupidity. As far as I can tell from this thread, and from similar ones on urw, there isn't a single person, who actually understands the subject (whether qualified or not), who doesn't think earth/hull bonding is a necessity.

 

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!

 

That's one of the problems. It's more likely that if (and when) something goes wrong they will be safe, it will be someone else they kill. If they were only going to kill themselves then I (and possibly others) wouldn't be so concerned. That's their own choice which everyone is entitled to.

 

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!

 

I can't read anything else into it.

 

Gibbo

Edited November 18, 2006 by Gibbo

[tomsk]

Right, thats it, I'm selling up...... My boat is dissolving, I am going to electricute all fauna (including swimmers) in the cut.

 

if I bond I'm wrong, If I don't bond I'm wrong.. Though reasonably conversant in matters technical I have not a clue as to what the majority of these posts mean, they could be right, they could be wrong......I am going to revert to living in my 5 berth coracle (with integral knurdling spar), sans shoreline and anything liable to be affected by matters galvanic. It is, i feel the only way forward

[Gibbo]

Right, thats it, I'm selling up...... My boat is dissolving, I am going to electricute all fauna (including swimmers) in the cut.

 

NO!!! Just one or the other, take your pic!

 

if I bond I'm wrong,

 

You might dissolve your hull. But you can prevent this with an isolation transformer (definitely) or with a GI (possibly).

 

If I don't bond I'm wrong.

 

 

You might kill someone.

 

Though reasonably conversant in matters technical I have not a clue as to what the majority of these posts mean, they could be right, they could be wrong......I am going to revert to living in my 5 berth coracle (with integral knurdling spar), sans shoreline and anything liable to be affected by matters galvanic. It is, i feel the only way forward

 

There's a lot of sense in that.

 

Gibbo

[chris w]

Gibbo

 

You should come off the fence and say what you really mean

[Gibbo]

Gibbo

 

You should come off the fence and say what you really mean

 

Someone else said a simllar thing but I'm far too polite and diplomatic

 

Gibbo

[blackrose]

If the boat only has a DC system it makes no difference whether it is bonded to the hull or not.

 

However if it not bonded, an accidental bond from positive to hull (maybe just a partial one) then leaves enormous scope for stray current erosion.

 

If there is an AC system on board then the DC system negative needs to be bonded to the AC system earth. The reason being to ensure correct operation of fuses, circuit breakers and RCDs in the event of a fault between 230 volts and the DC system otherwise you may end up with the DC system at 230 volts.

 

Gibbo

 

Thanks. I'm just trying to do the right thing. Chris Polley recommended two different studs in case a single stud came away from the hull, leaving AC & CD earths connected but not bonded to the hull. I'm assuming the yellow/green cable currently coming from the engine block to the single stud is the DC earth?

[John Orentas]

"Stray current erosion" What the hell is that, I have learned more new words and phrases in the past week than I have since leaving primary school.

[Guest]

"Stray current erosion" What the hell is that, I have learned more new words and phrases in the past week than I have since leaving primary school.

I'll stab a guess: It is erosion caused by stray currents.

[chris w]

There's a company I've never heard of called "SmartGauge" who have a passage on this - basically caused by having multiple earth points on the hull. http://64.233.183.104/search?q=cache:7hZQf...t=clnk&cd=1

 

Chris

Edited November 18, 2006 by chris w

[DHutch]

Mmmm, not that anyone on here has any conection to said website...

[ChrisPy]

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?

that's exactly where I drilled for my earth bond studs (10mm machine screws). I didn't weld them but a seal weld between the bolt head and the underside of the overhanging swim plate sounds like a good idea. In that location its very easy to check each week as part of a routine inspection.

[blackrose]

that's exactly where I drilled for my earth bond studs (10mm machine screws). I didn't weld them but a seal weld between the bolt head and the underside of the overhanging swim plate sounds like a good idea. In that location its very easy to check each week as part of a routine inspection.

 

Is the earth bond between my engine and the earth stud my 12v earth, or is is just the engine earth (or is it the same thing?)

[John Orentas]

Is the earth bond between my engine and the earth stud my 12v earth, or is is just the engine earth (or is it the same thing?)

 

 

In my view we should not be talking about "Earths" in the context of boats, too many connotations you end up with the absurd talk of: boat earth, bank earth, mains earth and so on, totally confusing.

 

Much better to say "Ground".

[Gibbo]

"Stray current erosion" What the hell is that, I have learned more new words and phrases in the past week than I have since leaving primary school.

 

Stray current erosion is what you get when a current passes from the hull through water/moisture to another conductor. In effect the hull electroplates whatever the other conductor is.

 

It is very similar to galvanic erosion but in this case the current is from an external source, like the battery system rather than self generated.

 

As it is the positive electrode that dissappears (by plating the other electrode) you will appreciate that a positive bonded hull is going to be far worse in this respect than a negative bonded hull.

 

Stray current erosion was the reason car manufacturers moved from positive ground to negative ground.

 

Gibbo

 

Thanks. I'm just trying to do the right thing. Chris Polley recommended two different studs in case a single stud came away from the hull, leaving AC & CD earths connected but not bonded to the hull. I'm assuming the yellow/green cable currently coming from the engine block to the single stud is the DC earth?

 

Chris's advice makes perfect sense.

 

The yellow/green cable could be that, if it's coming from the engine block but if so it isn't really the right colour. Luckily electrons are colour blind so they don't really care.

 

The bonding from the DC system should be capable of carrying the full DC system current. So it should be thicker than (or at least the same size as) all your other DC cables. This assumes the system is fused properly. Often a lot of the system (especially the engine circuit) is not fused at all.

 

The AC bonding cable should be bigger than all the other AC cables (again assuming the system is fused correctly). This usually means 6 or 8mm^2 cable for the AC system.

 

The AC earth should be yellow/green stripes.

 

The DC system earth cable colour changes from day to day depending what the tossers in Europe decided at tea time the day before. If you use black everyone will know what it is.

 

Two separate bolts/studs/whatever right next to each other is definitely the way to go.

 

Gibbo

[ChrisPy]

Is the earth bond between my engine and the earth stud my 12v earth, or is is just the engine earth (or is it the same thing?)

If you've bought a simple sailaway like mine this would just be the engine wiring negative (earth) bond link.

 

All the negative cables in any new 12V wiring should be led to the same stud. Mine are all 'collected' on a 'floating' stud (not actually floating, but just fixed to the plywood backboard for convenience in the electrics cabinet near the DC distribution board where the positive cables terminate) then a single 40sq.mm cable links this to the hull bond stud in the engine space.

[smileypete]

Hi,

 

I'll bet that <1% of fatailities and serious injuries on boats are due to mains electrics.

 

The best way to get that to 0.01% is to ensure all shorelines are RCD protected.

 

Then what about the other 99% or 99.99%, don't these deserve expert attention???

 

cheers,

Pete.

Edited November 19, 2006 by smileypete

[ChrisPy]

Hi,

 

I'll bet that <1% of fatailities and serious injuries on boats are due to mains electrics.

 

The best way to get that to 0.01% is to ensure all shorelines are RCD protected.

 

Then what about the other 99% or 99.99%, don't these deserve expert attention???

 

cheers,

Pete.

............... so, what are the root causes of the remaining 99% ? If you can tell us that then we can begin to address the problem.

 

oh, I am bombarded with safety initiatives by BP Worldwide every working day, so I regret I am getting slightly cynical about safety management, which IMHO should be all about common sense, and things within our power to fix ............ you know, like bonding the hull to earth.

[Yoda]

I can tell you that there is never one thing that causes an accident. What you can humanly do to stop people hurting themselves will be wasted by just one person doing their own thing. The whole history of aircraft accidents usually find something like three steps or related causes for the finale.

[Gibbo]

Hi,

 

I'll bet that <1% of fatailities and serious injuries on boats are due to mains electrics.

 

The best way to get that to 0.01% is to ensure all shorelines are RCD protected.

 

And bond earth/hull

 

Then what about the other 99% or 99.99%, don't these deserve expert attention???

 

cheers,

Pete.

 

Yep, but don't look at me. I know sod all about the subjects. So I don't consider myself qualified to comment on them.

 

Gibbo

[chris w]

You're leading with your chin Gibbo, but I'll resist the temptation

[Chris Lingwood]

I'll bet that <1% of fatalities and serious injuries on boats are due to mains electrics.

 

So what are people trying to do? Make that figure higher? Have we not met our quota yet?

[miles beyond]

Interesting reading all the weekend posts.

 

"There are actually 2 sides to this argument. One side argues that the entire electrical system should be isolated from the hull. The other side argues that it should be bonded but that certain precautions should be taken. Both systems have their pros and cons. This is an argument that has ensued for many years and probably will continue for many more..."

 

Copied and pasted from the Smart Gauge Electronics link kindly provided by Chris W.

 

It is of course a BSS requirement for boats to be fitted with ither an RCD or fuses, although I prefer the RCD option.

 

There are three residential boats where I moor. Not one has earth bonding to the hull, and one of them is inhabited by a man with 25 years experience and a wealth of technical hands-on boat knowledge. So he and I are in one camp, which as stated above, has its "pros and cons".

 

I do object to the extreme idea that not to bond the earth to the hull makes one a potential killer - that is simply farcical and incorrect unless you believe that an RCD won't work - in my case both the boat's and the mooring's separate one. They do work by the way.

 

This really is an issue on which we have to agree to disagree until firm evidence demonstrates that there is a real danger, or not. The electric drowning issue, raised by Gibbo, has failed to produce one example in the UK or answered the fact that the waterways are not experiencing an abnormally high level of dead mammals floating about in them. We also have about 20 ducks here - none of the crispy fried variety.

 

It is all very well providing links to obscure US sites about this last matter. The trouble is that if you want to you can find proof on the web that the earth only started 10,000 years ago and we are all descended from Adam & Eve, you may find all the evidence you want to demonstrate that the da Vinci Code is actually a true story, or even stretching all bounds of credibility, that Port Vale play the greatest football outside of Brazil.

 

You choose. I have, but there are two sides to this and a little less judgmental self-righteousness from some on this topic would not go amiss.

 

Fin.

[ChrisPy]

standard mains domestic wiring practice requires all metallic objects to be bonded to earth to avoid electrocution. in a house this bond could be via copper water pipe that is electrically continuous to the earth. for example check the kitchen sink, etc.

 

so why on earth would you not bond your largest metallic object to earth?