Electric winches. Are they

[rogerthebodger]

[ QUOTE ]
would reiterate, though, no earth connection is required to any part of your system to make these breakers work.

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Very Very wrong.

You are correct thast RCD trip when there is a difference in current in the L and N conductors. The only way there can be a differance is a leak through earth and <span style="color:red"> </span> back to the nutral line which MUST be also connected to earth at the supply point (inverter or generator) <span style="color:black"> </span>

If there is no earth connection at the supply there can be no current flow outside the L / N circuit and thus no trip.

In my case there was no earth commection at the generator and therefore no circuit outside the L / N connectors. and the shock was the current through me retirning through the Neutral line thus no differencr in the RCD and no trip.

In my case the current could not have neem a difect short through me as I would not be writing this.

If you can see what I mean even with a RCD in circuit is there is no alternate path outside the RCD L / N no trip. This alternate path is from the appliance to earth and back to the neutral connector via its connection to earth.

INHO using any mains device which can become covered in water as on deck is very dangerous even with an RCD and more so if the neutral of the supply device is not also earthed.

 

[Anonymous]

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Very Very wrong.

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That sort of adversarial post does not inspire me to spend any more time explaining it to you. I am an electrical engineer. Clearly you are not.

 

[rogerthebodger]

[ QUOTE ]
I am an electrical engineer. Clearly you are not.

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Again wrong both electrical, digitial control and mechanical design engineer many years in electrical distribution systems, logic control design, mechanical design engineering and now software design for both embeded software and user operated software systems. The only electrionic design I have not been involved in the electronic analogue systems.

What I have stated is basid first year distributions system design not rocket science.

Most people get fixated on the appliance side and dont look at the supply side as this is in most cases installed by the power network suppliers, npower in the UK escom in south africa etc.

and this kind of insultes just because you disagree in unbecoming and as I think you would agree boats are a very different enviroment to normal household setup from the mains electrical point of view with a much greater potential of electrical shocks and death from unsafe installations and usages. I would hate to think someone wak killed with lesser engineering knowlege that you of I due to taking advice withou the necessary care being taken

 

[Sailfree]

Fergus has posted about Tools Plus for the Milwaukee 28V battery drill.

When I first posted about this in February "rogershaw" kindly put links to 2 types of winch bits both available on the US e bay site.

There is The Cranker which is a square end that fits the winch and sells for about $20 plus P & P or there is another that is the exact 8 splines in stainless steel that sells at $45 plus P & P. I bought the latter. There were no import duty or VAT charged on it when I received it.

See RogerShaw's post dated 13th February 2007.

Trust this helps.

 

[Anonymous]

Yes, many thanks

 

[Anonymous]

As I have tried to explain to you, no earth connection is required to make an RCD work i.e. the RCD will protect the system without deliberately putting an earth onto the system. An RCD will operate if for any reason the outgoing current is not equal to the return current. If you got a shock in the way you outlined earlier then something somewhere was tied to earth back towards the generator either deliberately, accidentally, or by fault.

That is NOT the same as suggesting that an RCD requires an earth to work, which it does not. Of course, if you get a shock to earth then the circuit has to be complete i.e. there must be some connection to earth (maybe through a fault such as a damp piece of insulation, tracking, etc.).

It would be very misleading to people to leave the impression that a two wire system cannot be protected by an RCB - indeed, an RCB is particularly important in a two wire system. It was the introduction of doubly insulated equipment such as drills, hedge trimmer, lawnmowers that made RCBs such a vital part of modern mains wiring. This is just as valid on boats as it is in houses, - indeed, maybe more so but I don't want to evolve this thread into a course on mains electricity.

In your case the RCD breaker should have tripped if the fault current was greater than 30 mA. I don't know why it didn't but most likely, as I have already explained to you, it was less than the trip level of 30 mA. A 10mA shock can be quite a nasty tingle.

 

[rogerthebodger]

Sorry I have not replied sooner as I was on my new yacht the weekend.


[ QUOTE ]
RCD will protect the system without deliberately putting an earth onto the system.

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and the RCD trips when there is a differance greater the 30 mA between the live and neutral

So where does the differance in current go to because Kirchhoff's law states the sum of currents at a junction must be zero.

My answer is that this current will flow through the earth and back to the neutral of the generator or inverter.

This means the neutral of the generator must also be connected to earth for this to be effective.

My view is that if there is no connection between the neutral and earth at the generator this leakage current cannot flow so the RCD will not trip.

In fact if you look in Nigel Calder's Boatowner's mechanical and electrical manual it specifically states the the neutral and earth must be connected at the generator of an onboard generator and the same would apply to an inverter.

I my case as described the neutral / earth of my honda generator was not connected to earth so the leakage current could not flow through me to earth and through the earth back to the neutral of the generator thus bypassing the RCD and causing it to trip due to the differance in the current in live and neutral.

The current could only flow back to the neutral of the generator down the neutral down the neutral line through the RCD, thus no differance in current to cause the RCD to trip.

The whole point of this is not to assume an RCD in circuit will protect under all condition and the post that recomendated the use of a mains powerd drill to power the winch can be very dangrous

My main point is to ensure that the neutral of your onboard generator / inverter is connected to earth as stated by Calder in his very good referance book.

 

[Anonymous]

[ QUOTE ]
my case as described the neutral / earth of my Honda generator was not connected to earth so the leakage current could not flow through me to earth and through the earth back to the neutral of the generator thus bypassing the RCD and causing it to trip due to the differance in the current in live and neutral.

The current could only flow back to the neutral of the generator down the neutral down the neutral line through the RCD, thus no differance in current to cause the RCD to trip.

[/ QUOTE ] Sorry, I really don't understand what you are saying...could you try to express it in other words? If you got a shock then current went through your body to earth. What you thought was not connected might have been connected through incorrect wiring or tracking in connectors, for example. As I have explained twice, you can get a shock without the RCD tripping if the current is less than 30mA.

[ QUOTE ]
My main point is to ensure that the neutral of your onboard generator / inverter is connected to earth as stated by Calder in his very good referance book.

[/ QUOTE ]You don't say which of Nigel Calder's books you are talking about but I have seldom taken issue with anything he has written. However, be warned that if you connect your ship's wiring to ship's seawater earth then when you connect your boat to most shore power systems you will be in big trouble as most dockside earths are a long way from actual local earth, a large fault current can flow, causing terrible underwater electrolysis (corrosion).

 

[rogerthebodger]

[ QUOTE ]
Sorry, I really don't understand what you are saying...could you try to express it in other words? If you got a shock then current went through your body to earth. What you thought was not connected might have been connected through incorrect wiring or tracking in connectors, for example. As I have explained twice, you can get a shock without the RCD tripping if the current is less than 30mA.


[/ QUOTE ]

The Honda suitcase generator was siting on the dock starnding on its rubber anti vibration feet so the case of the generator cood not be grounded. I had the generator running and I had my extension box connected to the power outlet of the generator. My distribution box has built in a RCD and overload breakers for each socket outlet and 16 amp non fused 3 pin outlets being standard for south africa). My extension cable was pluged into the distribution box. I by accident kicked the line socket on the end of the extension into the water of the marina, the generator started to labour but the overloads or the RCD did not trip and when I pulled the cable out of the water the gentrator stoped labouring but I got a shock and again the RCD did not trip. When I made it generator safe I tested the RCD with aleakage current tester with a switch that can set earth leakege current like this and all was OK so the only conclusion that the current that gave me the shock went back down the extension lead back through the neutral sa there was no other path as I said the generator was not earthed so the leakage current could not have flowed that way.

You could be correct that the current could have been less than 30mA but it gave me quilt a jolt and I only felt it in my arm so did not seem to pass through the main part of my body and after this I make shure the generator is earthed by droping an wire connected to the case and neutral into the water near by.

TheNigel Calder's book I refer to is titled "Boatowner's Mechanical and electrical manual second edition and on page 96 Figure 3-21C "An onboard generator has its neutral and ground wires tied together at the generator case and nowhere else"

The picture shows the ground connectd to the norman ground simble and the words Boat's ground.

As I said inverters can be considered the same and alot of people fit inverters without proper connection of the neutral to ground and infact in a previous thread a boat builder said " who in his right mine would connect neutral to ground"

For shore power no neutral / earth connection should be made as this is done at the distribution companies transformer substation at the very least.


[ QUOTE ]
However, be warned that if you connect your ship's wiring to ship's seawater earth then when you connect your boat to most shore power systems you will be in big trouble as most dockside earths are a long way from actual local earth, a large fault current can flow, causing terrible underwater electrolys


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I know this very as the yacht I am building has a steel hull and deck and the internal generator / inverter must be connected to the hull for safety (all stainless hand rails etc electrical connected to hull) so my shore power earth will have a galvanic isolator between the shore power incomming ground and the boats onboard generator / invertor ground.

Now the next thing I need to sortout is the SSB grounding of which I think you know all about but that will be for another day.

Thanks Lemain and I hope you did not take offence to some of my previous comments

 

[Anonymous]

[ QUOTE ]
I had my extension box connected to the power outlet of the generator. My distribution box has built in a RCD and overload breakers for each socket outlet and 16 amp non fused 3 pin outlets being standard for south africa). My extension cable was pluged into the distribution box.

[/ QUOTE ]I'm beginning to see your problem here. You think that if a generator is sitting on rubber feet there can be no connection to ground? Surely the generator chassis was connected through the extension leads' E connections all the way to the end of the cable? So if the cable is wet with conductive salt water, there can easily be an earth reference perfectly capable of causing an electric shock.

I can guess what probably happened. When you dropped the mains socket in the water a current flowed between L & N which is why the engine note changed. The E terminal was not carrying a significant load so should have been tied to local Earth (sea). As nothing at the generator end was connected to local earth no current flowed back to it and the RCB did not trip but now the chassis of the generator is tied to local Earth (sea) Remember, there was a high fault current (engine labouring) so all the current was from L to N which of course is not designed to trip the RCB!

When you pulled the wet cable out of the water the current dropped as there was no electrolyte but it would still have been tracking across the wet terminals and the wet cable was in contact with the ground (which you were standing on). So there was still an Earth reference and L was able to track across.

The fact that you got a shock proves that there was a return to earth somewhere it seems probable that it was from the E terminal in the cable to the wet cable cover to the ground. The RCB should have protected you and probably did but the current was less than 30 mA.

As for grounding generators, my own system runs with no tied earth, not to seawater or the dockside. We float, electrically as well as in the Archimedes sense.

No offence taken! /forums/images/graemlins/smile.gif The point is that the generator WAS earthed, by the seawater!

These things are always difficult to put into words without diagrams and I am not set up for posting diagrams right now.

 

[rogerthebodger]

The one extra bit of info I forgot was that the generator frame was connected to the earth lead as is usual in an appliance but no connection between the frame / earth and the neutral as is usual on the supply side of an electrical distribution network which in fact defines which is the neutral connection of the supply network.

If there had been this earth / neutral connection some current would flow back through the neutral and some back through the earth, the amounts in each depending on the resistance of each path but even if the current in the earth was small (larger than the 30mA RCD trip point) the RCD would have triped as soon as the extension went into the water.

Not having this neutral /earth connection at the generator prevented the leakage current flowing in the earth line and thus the shock from leakage current on the outside of the wet cable and not having a IMHO correctly connected earth / neutral connection preventing the RCD operating correctly

When I found no earth /neutral connection on a Honda generator I was surprised as I had installed standby generators and UPS's in the computer industry where it is the norm to connect earth and neutral, I investigated further and found the same with inverters I had came across.

The one problem that can be caused by having earth / neutral connection is an incorrect phase connection. This is mostly in a shore power connection but also in an onboard generator connection but can be checked with that earth leakage tester posted early or as I have incorporated a neon indicator between live and earth (green) and neutral and earth (red) and yes it will introduce an additional earth current but only about 2-3 mA way below the RCD trip point.

A very interesting discussion on earthing systems here which shows a system with on earth / neutral connection called IT network and under safety says "In IT and TN-C networks, residual current devices are far less likely to detect an insulation fault. In a TN-C system, they would also be very vulnerable to unwanted triggering from contact between earth conductors of circuits on different RCDs or with real ground, thus making their use impracticable. Also, RCDs usually isolate the neutral core, and it is dangerous to do this in a TN-C system."

 

[Anonymous]

I've just had an email via ybw advising of a reply by you to my last message starting... " The one extra bit of info...." which isn't on the board. Strange unless you deleted it? And there it is now on the board. Must be a problem with YBW at the moment, it has been very slow.

 

[Anonymous]

Had you connected the E and N at the generator, and connected it to an earth stake, your supply would not have been floating and would have been inherently more dangerous. In building sites it is common practice to use isolating transformers so that the mains is floating, that way, if you touch either L or N you will not get a shock but it for whatever reason (e.g. fault) you were to get a shock then the RCD would trip. The output of the generator's alternator is electrically similar to the secondary of an isolating transformer, so why earth it in outdoor applications?

Earthing is a valuable safety tool in some cases and you can read up on it but please be aware that boats are mobile and you need a system that will be compatible with anything you might find on the dockside - and there is never a label on the dockside supply telling you what the system is. Furthermore, if you get your earthing wrong on a boat you will cause problems of electrolysis.

This discussion has stemmed from someone criticising a poster for suggesting a mains drill for driving a winch. As I have tried to explain, in good weather with a modicum of common sense, this is not the problem you might think it is.

This discussion has also drifted into the other discussion on earthing generators so we have a bit of a dog's breakfast.

Earthing is a big subject, I don't have Nigel Calder's book that you referred to and though I seldom disagree with him if he recommends connecting ship's N to seawater earth then I suggest people take some other advice before blindly following that suggestion. Indeed, if you did that and plugged into a 'split phase' shorepower system you would blow all the mains fuses and might damage your boat wiring, or equipment. You would never know that your shore power was 'split phase' and while you might not find it these days in Europe I would bet that you will find it elsewhere around the world.

RCDs protect people downstream of them regardless of how the upstream supply is earthed. That is because people get shocks by electricity passing to earth so if the shock potential exists then some connection at the upstream end MUST be there, albeit unintentionally, due to dampness, tracking, damaged equipment, faulty installation, etc. You ARE protected downstream of an RCD - period.

I'm going to duck out of this discussion now, as I think it is going to further muddy the water especially for those for whom electricity is a bit of a black art anyway.

 

[rogerthebodger]

Well lets agree to differ on this one and let people consider both points of view and then make their own mind up on this one.

 

[Goldie]

Or take the simple, safe mechanical route /forums/images/graemlins/tongue.gif which is where I came in: a geared winch handle!!