DC conductor to hull.

[OptedOut]

Yes, but is there anything that can be done to speed up the process.

 

Nope, can take a million years.

[Guest TerryL]

name='Gibbo' date='Nov 14 2008, 01:19 PM' post='298014']

So you are saying a short to hull is an impossible scenario?

 

Why does anyone put fuses in then?

Very difficult with an isolated system to get a short to the hull, it needs two faults together. That also means two damp cables touching the hull!

I don't know of many with fuses on their battery, hence an isolated system is safer.

 

See my other post. You need to learn the reason the MOD sometimes (not always) use an isolated DC system. You can only learn this reason by actually being involved with the MOD. You know, working with them, designing equipment and systems with and for them. Like we do (yes, do some searches for MOD contracts and see how many times my company name turns up). I bet your plumbing company isn't in there. You can't learn this by being an armchair expert.

I did my learning in the military, working with the stuff, is that involved enough? Not as a civvy sitting behind a desk like you, funny, I never came across any of your stuff anywhere.

 

The usal beginners point is "but it doesn't measure anything in the ground conductor, it measures the difference between the live and neutral currents". Yes, we all know that. But is appears that you don't know that there can't be any difference unless there is an earth path back to the supply before the RCD.

You mean Chris doesn't know that and you don't know that putting a resistor between neutral and earth will trip an RCD when enough current is flowing to make an imbalance and it is the sort of tinkering with 230 volts that makes your sort dangerous. You don't know the other implications.

 

I think you're doing it again. Attributing things to people who didn't say it.

Where have I incorrectly stated what the fault current should be for a GI?

No I'm not. See post 128 galvanic isolators. How can 16 amps be full fault current?

 

The problem I have with it is that in order to comply with regs (ABYC being the only ones at present) the GI has to be capable of carrying full fault current indefinitely. That means 15/16 amps in UK cases which at 2.4 volts is a fair amount of heat to get rid of. Even at 1.2 volts it's going to get hot.

 

Gibbo

When are you going to explain exactly how my boat is going to suffer electrical erosion through damp. BTW the cables and batteries were bone dry today when I checked!

 

See what I'm up against folks?

Edited November 15, 2008 by NB Alnwick

[OptedOut]

OK, back to the start, shall I,

 

1) Ground the battery bank to the hull?

 

2) Isolate the Eberspacher from the hull?

Edited November 15, 2008 by OptedOut

[Guest TerryL]

OK, back to the start, shall I,

 

1) Ground the battery bank to the hull?

 

2) Isolate the Eberspacher from the hull?

3) Hold these wires! You've caused enough trouble. No point in me giving you another sensible answer, I'm not allowed an experienced independent view, listen to the upstarts while they still know everything.

[Roger Gunkel]

3) Hold these wires! You've caused enough trouble. No point in me giving you another sensible answer, I'm not allowed an experienced independent view, listen to the upstarts while they still know everything.

I know, lets just fight everyone on the forum, they're all idiots anyway!

 

Roger

[OptedOut]

3) Hold these wires! You've caused enough trouble. No point in me giving you another sensible answer, I'm not allowed an experienced independent view, listen to the upstarts while they still know everything.

 

Thank you. To eliminate any further bad feeling I will withdraw to consider ALL the advice given and draw a conclusion, possibly aided by further research.

[bottle]

I don't agree they are all idiots, So only you is correct just a few who get all touchy because I stick to my views and won't cave in under pressure on some stupid disagreement.Just as you do Why should I agree with Gibbo, is he a god or something? No, Gibbo nor anyone else believes themselves to be a god. You seem to believe that you are the only one that is always correct and only a god is.You are the bullies! No, we are normal people that can make up our own minds. Do you and your gang want to come round and put the boot in as well? No, actually I have some pity for you, you need treatment (this is given in good faith as someone that has dealt with and suffered with mental health problems) I wouldn't put it past you. Fools, grow up! I think that maybe it is you that needs to but of course as mentioned before it may be a mental health problem.

 

I apologise for telling you to %$*^ off, it was a momentary loss of control but I still wish you would go and play elswhere.

[Guest]

Edited out; can't be arsed with the flamer anymore. He will eventually disappear up his own a**ehole.

Edited November 15, 2008 by Guest

[Pretty Funked Up]

OK, back to the start, shall I,

 

1) Ground the battery bank to the hull?

 

2) Isolate the Eberspacher from the hull?

 

Are eberspachers chassis grounded?

[Guest TerryL]

Thank you. To eliminate any further bad feeling I will withdraw to consider ALL the advice given and draw a conclusion, possibly aided by further research.

Before you go, amongst my collection of marine engineering books I have a Lucas CAV Marine electrical systems booklet which is very informative and clearly states that DC systems should be two wire and insulated. My boat was built to Lloyds standard and a two wire insulated CAV system was specified by the Naval architect. This is a quality installation and I have had no problems whatsoever. It is also far safer to work on as tools etc. cannot short to the hull and is a far more common system than is realised.

 

Page one quote: Electrical systems should be wired as insulated return systems; that is using two insulated cables. It has frequently been the practice to earth either the positive or negative poles of generators or starters. In this case insulation failure on the opposite or negative pole results in short circuit conditions or leakage current wh.ich can produce electrolytic action on tanks, pipes, electrical equipment and underwater equipment.

Page 28 quote: Insulated return systems are recommended and the Lucas/CAV marine range of alternators, dynamos and starter motors are all insulated return types. With earth return systems leakage occurs if insulation of the insulated pole becomes defective. This happens when junction boxes are positioned in damp or leaky locations, where starter motors or dynamos are subject to oil or water ingress and from badly installed deck sockets and external electrical fittings.

 

Insulation faults, particularly in earth return systems may produce stray currents which flow through the seawater between underwater fittings, such as propellors, shafts and "A" brackets. This results in corrosion of the fittings through the loss of metal by electrolytic action and it should be noted that leakage current of the order of 250-500 milliamps is not uncommon and attack is then both rapid and severe.

 

It goes on to say that earth lamps connected in series with the main bus-bars should be checked frequently for early warnings of leakage currents.

This all ties in with what I was taught in the military and have experienced in my marine business and in fifty years of electrical knowledge. Negative return systems on engines are now common due to automotive equipment being used and therefore there is no choice. It is your choice whether you keep the insulated return system and convert earth return equipment or you simply convert your existing system to negative earth. There are clearly considerations either way. For my own choice I would be reluctant to lose the system I have and would look at the practicalities of converting the eberspacher connections, it is only the negative that is likely to be earthed with a fault in any event and so is no worse than a permanent negative earth connection. Edited November 15, 2008 by NB Alnwick

[Gibbo]

So who do you believe?

 

The Recreational Craft Directive, the American Boat and Yacht Council, The Biritish Marine Electronics Association, Nigel Calder....

 

Or.........

 

A plumber?

 

"the ISO" (assuming he actually means the correct one) does not specifiy the system should be isolated.

 

Further, from Payne's book "The Marine Electrical and Electronics Bible" (yes the one this plumber keeps going on about).... section 6.19......

 

<quote>

 

It is a recommended practice in the most common wiring configuration for the negative terminal of the battery to be bonded to the ground point. In many cases this point is the engine block. This is done to polarise the DC electrical system.

 

</quote>

 

So it seems that John Payne also disagrees with this plumber in that he states the DC system should be bonded to the hull. Contrary to the plumber's viewpoint.

 

From the same book, section 8.8......

 

<quote>

 

DC Circuit leakage currents.The most common DC leakage currents are (a) leakage across condensation or conductive salt deposits in DC circuit connections and junction boxes and ( tracking or surface leakages across the top of a battery to the positive terminal, caused by moisture and dust accumulattion.

 

</quote>

 

So John Payne also disagrees with the plumber on this point in that John Payne states that DC circuit leakage is a problem yet the plumber says it isn't.

 

If you want to know about marine electronics or electrical systems do not ask a plumber. Particularly this one.

 

This is my last post on the subject. When (not if) the plumber comes back with silly counter arguments ask him to cite references which he won't be able to do for the simple reason that he is on his own in the viewpoint. Simply because he is wrong.

 

Gibbo

[ChrisPy]

if everyone blocks the flamer then he can carry on in blissful ignorance and we can ignore him.

everyone wins.

 

he's blocked - as of now.

[bottle]

Like wise.

[carlt]

If people, who don't like the ignore lists could refrain from quoting him, too.

[OptedOut]

Are eberspachers chassis grounded?

 

Back again. The full story, I was blissfully unaware of any potential problem until my copper engine room towel drying rail came into contact with the alternator positive and engine room floor plate, ZZZAP.

Got meter out and eventually found the Eberspacher was the problem, disconnected the socket in the loom to this unit and diagnosis confirmed.

Rang Eberspacher who confirmed that the glow pin igniter was grounded to the case, they were looking into this but only from a galvanic point of view.

Eberspacher suggested that they could supply a rubber pipe to break the fuel line connection and made some suggestions as to how to isolate the exhaust.

The unit is mounted on non-conducting material

The high resistance of the plastic pipes and water therein was calculated as a negligable risk.

 

My own view is that I would prefer to keep the DC as it was, no connection to the hull anywhere and put up with the slight complication of charging the engine battery from the single alternator.

 

It would appear both systems have pros/cons regarding safety.

Edited November 15, 2008 by OptedOut

[MoominPapa]

Back again. The full story, I was blissfully unaware of any potential problem until my copper engine room towel drying rail came into contact with the alternator positive and engine room floor plate, ZZZAP.

......

Eberspacher suggested that they could supply a rubber pipe to break the fuel line connection and made some suggestions as to how to isolate the exhaust.

.....

It would appear both systems have pros/cons regarding safety.

It's difficult to see any safety pros in a system which sends the fault current through a metal diesel fuel pipe in the event of a short to the hull. IMHO this is a perfect illustration of why there should be a big, beefy, low resistance, high current, mechanically reliable bond from the battery negative straight to the hull.

 

MP.

[Guest]

It's difficult to see any safety pros in a system which sends the fault current through a metal diesel fuel pipe in the event of a short to the hull. IMHO this is a perfect illustration of why there should be a big, beefy, low resistance, high current, mechanically reliable bond from the battery negative straight to the hull.

 

MP.

Amen

[Smelly]

You know, the advantage of going to the pub over sitting online ranting all the time is that even if a fight hasn't started then usually a party to a -ahem- "discussion" has been ostracized to the point that they've gone home and doesn't come back. You rarely get the same argument twice.

 

You can probably tell that I've just clicked to the end of the thread but, in the absence of any bare knuckle action I'm going to go off and find the "block" button, it ain't funny anymore.

[OptedOut]

It's difficult to see any safety pros in a system which sends the fault current through a metal diesel fuel pipe in the event of a short to the hull. IMHO this is a perfect illustration of why there should be a big, beefy, low resistance, high current, mechanically reliable bond from the battery negative straight to the hull.

 

MP.

 

I DID NOT say there were any pro's in allowing a heavy fault current through the Eberspacher, that was the whole purpose of my enquiry.

I implied there were pros & cons for an isolated system that included isolating the Eberspacher from the hull.

[RLWP]

I had a lovely time this morning visiting the boat to sweep the leaves off the roof. Met two single-handers who joined up to work down Hatton together. It was really nice to find some sensible boaters who were prepared to work together and cooperate.

 

Richard

[Gibbo]

Oh I forgot to add......

 

You can read the relevant page from Payne's book here.............

 

http://books.google.co.uk/books?id=j3B_0y_...1&ct=result

 

Gibbo

[smileypete]

I DID NOT say there were any pro's in allowing a heavy fault current through the Eberspacher, that was the whole purpose of my enquiry.

I implied there were pros & cons for an isolated system that included isolating the Eberspacher from the hull.

 

If you're worried about this sort of fault, a fuse/circuit breaker can be added into the negative supply to the Eberspacher to give 'double pole' protection (protection on both supply connections).

 

cheers,

Pete.

[OptedOut]

If you're worried about this sort of fault, a fuse/circuit breaker can be added into the negative supply to the Eberspacher to give 'double pole' protection (protection on both supply connections).

 

cheers,

Pete.

 

Thanks, I'll probably modify bits of the set-up during the winter.