Earthing a generator (again) - Is there a choice??

[ QUOTE ]
Richard,

The purpose of my post was to convey the necessity of always having an RCD and an overload protector (breaker or fuse) at the supply end.


[/ QUOTE ]

Understood.

"My RCCB, (which I believe is both the 30mA RCD and the 25A Circuit breaker), is on the distribution panel, probably about 15ft from where the shore supply, (or generator supply), enters the boat. I suppose I could get a box and fit another RCCB in the aft locker, (lazarette?), but would you suggest that is necessary?"

Does this sound OK?

Richard
 
I am sorry but the advice of Plomong is unsafe. Ignore it.

The basic rules are that there must be a full earth path that goes via an "earth" that is connected to the neutral BEFORE the RCD WITHIN the generating apparatus. All metal is then connected to this earth.

RCDS DO NOT WORK WITHOUT A SEPARATE ROUTE BACK THAT BYPASSES THE RCD.

Using an RCD on an isolated supply is a danger as it gives the user a false sense of security. RCD are ONLY designed for full earth systems.

Even then you should always run one of the polarity/earth tester plugs with the 3 neons to make sure the earth is connected at all times. A single fault of a break in the earth will render the RCD useless.

http://www.homesteadcaravans.co.uk/images/uploaded/Mains_Polarity_Tester.jpg




If you go for isolating then you must have test circuits that work and detect the first fault. Isolated system need 2 faults to kill. They are specialized and require knowledge of how to protect life and how to maintain safety. They are generally not used with the normal public. Aluminium super yachts are a good examples.

Same with centre tapped 110v situations to which Plomong referes. These are also only for specilaist use as normal plugs with 1 fuse are not adequate. You have to fuse both as they are 2 phases without any neutral. This can not be mixed with normal domestic appliances or unisolated shore power. VERY dangerous suggestion.

Also references to combined shore and generator are wrong. The key is in any system there should be only one source of power. It should be through a selector switch that avoids 2 sources at all costs. Carling make a breaker system with an interlock. It takes time to switch between the supplies and avoids overcurrent situation with motors. A simple selector switch is not adequate. However, the earth to the case should be connected through permanently. The example is that when connected to shore power you should be able to run the generator engine, and the frame should still be earthed to the shore earth. However, the generator high voltage output should be totaly unconnected.
 
Having been involved with the discussions from the start I agree that an RCD (RCCB) must have an earth path back to the neutral for it to work at all, so again IMHO no point on an isoulated system.

There is one point I would question you on is

[ QUOTE ]
A simple selector switch is not adequate. However, the earth to the case should be connected through permanently. The example is that when connected to shore power you should be able to run the generator engine, and the frame should still be earthed to the shore earth

[/ QUOTE ]

I have a 4 way 3 pole break before make selector to select between shore, generator , invertor and off. this switch both line and neutral and the third pole is for the earth.

the princpal of earth is that there must only be one neutral / earth connection at the supply which is on the boat for a generator / invertor but will be at the sub station in the case of shore power not using an isoulating transformer so when my switch is in the shore power position the shore earth will be connected to the boats earth circuit but when the switch is in the local generator or invertor position the shore earth will be disconnected and the earth will be connected to the invertor / generator neutral.

Unless you mean the shore earth should be connected to the generator case but not to the generator neutral when shore power is connected.

I agree under NO CIRCOMSTANCES should either the line or neutral of the generator, invortor or shore power be connected together AT ANY TIME.

Just a not to all its is the connection of one side or the two supply wires to earth that defines it to be neutral and nothing else, so it can be very easy to get the connection incorrect in a strange marina shore power lead. I have therefore connected neons (same as used in the tester posted by solarneil) in the shore power incomming conector to show this kind of fault before I switch my selector switch to the shore power lead.
 
Sorry to only respond now but I have spent the weekend trying to get my new yacht ready for comming summer

Reading Solarneil post I think he has said it all
RCD gives no protction on an isolated mains system as the most lickly place for a short would be between the RCD and appliance where the neutral / earth connection must be between the RCD and supply for an earth fault to be dectected by the RCD for the reasons discussed earler.
 
This debate baffles me. If it were ok to join the earth and the neutral then why do they bother with 3 wires in the first place?

I've got one of those neon testers (they're brilliant) and was shocked to discover that sockets on one side of the boat was correctly wired, and the other side had the live and neutral reversed! The fault was inside the main distribution panel. How did that happen and then go un-noticed for 20 years?
 
If you earth to the sea, what happens to someone in the water if you have a short?

I am quite happy with the concept (I Think??) of earthing back to shorebased power (provided the polarity is correct,) but I really cannot get my head round what happens to the shorted current with an onboard generator, other than connecting to the sea. I am not sure that I would be happy to be fried, whilst taking an incocent morning swim!
 
I was not going to get "sucked" into this,
BUT
I have read all the replies and feel I must for the safety of those that are reading these posts and MAY take some of the advice wrongly and POSSIBLY have an accident.

An RCCB should be fitted to the outlet supply at the generator

Fit an RCCB of 30ma trip current with a contact rating as near to but ABOVE the max amp output of the generator

An RCCB is NOT an overload circuit breaker/fuse the "25amp" rating of Richards RCCB is the contact rating of the Internal switch. ( I say this without seeing the device and presume it is a standard RCCB)

Normally a generator will be fitted with an MCB which will Trip if the demand exceeds this.
An RCCB as said should then be fitted to the output and then a fuse or MCB should be fitted at a rating to protect the circuit.

The only component that then could be dangerous is the"generator itself" and that only if it develops an internal fault causing the case to be "live"


Always fit an RCCB

Always fit an RCCB

Anyone that says it is not necessary or it wont work will have to justify their reasons
and I throw down the gauntlet.


As for the "grounding/earthing of the Generator itself to much confusion IMHO is being
created by incorporating shore power etc.

There are three different situations as far as I can see regarding "grounding the Generator"

(1) the boat is at sea
(2 the boat is in port/marina
(3 the boat is out of the water on the hard.

The main reason for this reply is to ensure That people do not think it is not necessary to invest and fit an RCCB, although I am not answering your "Is there a choice"

Yes there is a choice but the decision of choice can be affected by the situation ie:- (1), (2)or (3)
 
[ QUOTE ]
As for the "grounding/earthing of the Generator itself to much confusion IMHO is being
created by incorporating shore power etc.

There are three different situations as far as I can see regarding "grounding the Generator"

(1) the boat is at sea
(2 the boat is in port/marina
(3 the boat is out of the water on the hard.

Yes there is a choice but the decision of choice can be affected by the situation ie:- (1), (2)or (3)

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Hi Bill - I think this is a debate worth airing because most people who buy a portable generator just plug it into the boat shore supply.

As I said.... my RCCB is on the boat distribution panel, along with a polarity light, about 15ft from where the generator, (or shore power), plugs into the stern - I dont know how good this is - it has certainly tripped whenever there has been some problem with the cable and its' connections.

My personal use of the portable generator will be mainly for use at anchor - i.e. 1) boat at sea.

I wonder how you see this affecting the "choice".

Richard
 
SolarNeil

[ QUOTE ]
The basic rules are that there must be a full earth path that goes via an "earth" that is connected to the neutral BEFORE the RCD WITHIN the generating apparatus. All metal is then connected to this earth.

RCDS DO NOT WORK WITHOUT A SEPARATE ROUTE BACK THAT BYPASSES THE RCD.


[/ QUOTE ]

Quite right. I was not advocating earthing downstream of the RCD, but upstream of it, at the supply (generator), and definitely before the RCD.

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Using an RCD on an isolated supply is a danger as it gives the user a false sense of security. RCD are ONLY designed for full earth systems.


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Did I not say that a fully floating arrangement was a special case, and advised not going that route???

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They are specialized and require knowledge of how to protect life and how to maintain safety. They are generally not used with the normal public.

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This what I said: "There are some exceptions in certain types of industrial installation, but don't go that route. Those are very specialised situations and fully understood by those who design and maintain them."

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Also references to combined shore and generator are wrong.

[/ QUOTE ]
I did not say that both would be connected at the same time. I said "As for earthing arrangements when a generator is integrated with a shore supply and the boats 12V system, that brings in shore-side earth, isolating transformers, galvanic isolators, ships own earth to the sea, etc, etc. And I specifically tried to avoid those topics." Nowhere did I say both shore power and generator would be connected at the same time, only that an such an installation requires considering ... items that I specifically avoided.

Please be so kind as to read my post carefully again.

Plomong

"
 
You said:

Quote:
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BUT ONLY IF THE GENERATOR AND ALL DOWNSTREAM LOADS are an isolated system that is nowhere connected to shore power.

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What I said was that in a port situation it SHOULD be connected to the earth as the generator, when not working, is just a lump of metal that needs to be earthed like any other.


Quote:
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"If the supply is floating, ..... it is even more important ....structure are properly grounded. There are some exceptions ..."

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That was read as the special exceptions were when the structure was not grounded not that ANY isolated system is an exception that need special knowledge.
 
Hi Richard.
OK some or all what I am going to say you my know but other readers my not.

To get an "electric shock" you have to touch two different conductors at different potentials at the same time ie;- "live" & Neutral or "live' & Earth or possibly Neutral & Earth
The reason I say "possibly" Neutral & Earth is because if the installation is correct and all is correct normally there should be no voltage or a very low voltage between Neutral & Earth,and this voltage can be due to the difference in resistance of the cable or induction due to the wires being coiled together.

For example (exaggerated for explanation purpose) if a length of wire 10 mtrs has a resistance of 100ohms and it is your Neutral, and your Earth wire is only 1mtr long it will be 10ohms therefor the circuit will work ok and the current will flow happily around the circuit,but if you were to put a meter between the Neutral & Earth electricity will flow through the path of least resistance and divert through your meter showing a voltage but this will be low.so if your meter can sense a voltage so can your body albeit small

IF an RCCB is fitted this is a different situation.(explained with words in a way that I hope is easy to understand and not all technical and correct terminology)

The circuit inside the RCCB creates a small resistance in the Neutral wire Therefor making the neutral wire on the output side of the RCCB more sensitive to the Earth wire

An RCCB works by "seeing current flow out" of the RCCB say along the "Live"wire and waiting to "see the same current" return to the RCCB along the Neutral wire.
Example

100ma flows out on the "Live" wire goes round the circuit and 100ma flows back along the Neutral wire to the RCCD,
the RCCD senses this, and says ok all is good I will stay switched on.

IF however a fault develops and there is a "LEAK" somewhere 100ma flows out but only 69ma comes back it says very quickly switch off.

Now what happened to the 31ma ? well this went somewhere it shouldn't have done ie:- a component faulty or through a PERSON the person would suffer a shock but the RCCB will have switched off the supply before anyone hears you say "eff that"

So the above is why it is important to fit an RCCD.

OK But we have to consider all things so we get to the generator itself.
Now this should be quite safe to use without earthing it, BUT UNADVISABLE

BUT BUT BUT there is always a possibility that a fault can develope that causes the casing to become "LIVE"

OR OR OR that the wiring installation is not correct.

So you are at anchor and want to run your genny.

All is ok so you start up and all is good but you don't know the potential between the case of the genny and any other metal things.

precautions

(1) never touch the generator while it is running and touch another metal object (or put you foot in the sea) at the same time.

(2) normally all the metalwork on your boat is "bonded" together and goes to an anode in the water so if you made up a piece of wire with an anode and connected it to the genny case and put the anode in the water the risk of you getting a sever shock MAYBE less but it still exists because of the resistance of the sea water between the anodes and could be a hazard to swimmers

However if you are at anchor and it is a chain and not rope you could connect "earth to that BUT it will properly take all the galvanizing off!! UNADVISABLE

(3) When using a portable generator on your boat and you need to touch it make sure you don't touch anything else ore wear rubber gloves

Having said all that I never Earthed my generator frame/case BUT I always treated it with utmost respect if I had to go near it when it was running

Personally I would not "earth" my genny unless my boat was out of the water.

Although one would have to be very unlucky to be Killed by electric shock normally it is not the shock that does the damage it is the reaction it causes you to do like bang you head or break your arm or cuts etc when you react.
 
SolarNeil,

OK, I should have been clearer on several points.

However, the real issue here is how to bring Richard up to speed on basic electrical circuit arrangements in an organised manner.

IMHO this forum is not the best way to get a good grounding of the basic principles as applied to small boats. I don't know of any suitable books that he could source and read, so I suggested he try to get in direct contact with someone knowledgeable. I think he is now in Malta. So, does anyone know of someone who could be of help to Richard in malta???
 
[ QUOTE ]
Having said all that I never Earthed my generator frame/case BUT I always treated it with utmost respect if I had to go near it when it was running

Personally I would not "earth" my genny unless my boat was out of the water.



[/ QUOTE ]

OK - all understood, and probably along the lines of the conclusions I had reached, both in terms of how things work, and what to do, including the precautions. (And I certainly did not understand it before these discussions so I hope it has been worthwhile for more than just me).

The only outstanding thing, (for me, anyway), is what to do at the generator, with the earth wire in the cable from the portable generator to the boat power supply input, (shore power connector, for want of a better description).

The answers seem to me to be either leave it where it is, or connect it to the neutral as it enters the generator.

Connecting to neutral clearly provides a path back to the source of the power... which makes sense.

The result of leaving it where it is becomes subject to what happens to the earth part of the socket when it gets back into the generator..... On my previous generator, I could guess that it was connected to nothing, as all my internal testing stuff, (polarity light, and 3 neon tester), said/suggested there was no earth.

Logically it needs to be connected to something for at least the following reasons:

1) to provide a path for any fault leakages

2) to enable the RCCB to sense a leakage and open its' contact, without there having to be a human, (or something else), creating the path - thus identifying a fault.

Having said that, as per your description, the live comes out of the RCCB, then goes around the boats sockets and appliances, and the neutral goes back into the RCCB, so presumably the RCCB will trip if some current leaks via a human to earth, even if there is no earth wire carrying the leaked current back to the source. Furthermore, the RCCB has no effect/knowledge of any faults which might occur between it and the generator, so the closer the RCCB is to the shore power, the better, and an RCCB in the plug which is plugged into the generator would be best - If it's that straightforward, one would hope that a Honda generator would have an internal RCCB, or RCD.

It's getting clearer, and a little light went on re the RCCB this time.

Thanks again

Richard
 
[ QUOTE ]
I think he is now in Malta. So, does anyone know of someone who could be of help to Richard in malta???

[/ QUOTE ]

I am in Malta, but I think I almost understand what's going on, and I think/hope, that discussing it here will help others aswell as me.... even if it only makes some aware that there are issues and precautions necessary.

The problem here is that people who know what they are talking about post a bit of what they know, then somebody else says "Ah But...." and so on.

I could equate it to trying to explain the process of buying and financing a good letting property, finding a good agent, getting good tenants, maintenance, repair, cashflow, and so on... then the process of evicting bad tenants, (or getting possession from good tenants, for some reason).

I could write a book on my subject, (and I might), and anything I might ever say here would be only part of the story, leaving me open to "Ah But....".

All I think I am missing is what to do with the earth wire as it enters the generator, but I've said that in my reply to Bill.

In practical terms, when I get my new Honda generator and use it at anchor, I am either going to connect earth to neutral at the generator, or not, and I/we am/are going to be careful when going near the generator when it is running. I might get a plug with a built in RCCB, (or RCD), to plug into the generator.

Off to bed now - Janets coming tomorrow night, so I've got to change the boat from a batchelor pad to a cosy home before about 4pm tomorrow - Generators will be a long way from my mind!!

Thanks for all the help

Richard
 
Quote
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the live comes out of the RCCB, then goes around the boats sockets and appliances, and the neutral goes back into the RCCB, so presumably the RCCB will trip if some current leaks via a human to earth, even if there is no earth wire carrying the leaked current back to the source.
_______________________
Correct.. The problem is the "loose" use of the word "earth"
For current to flow through you it has got to go somewhere for you to get a shock.
If it doesn't go anywhere you will become "LIVE" like the thing you are touching until you touch something else at the same time.(like the bird sitting on the power line.)

_____________
Quote
an RCCB in the plug which is plugged into the generator would be best -

______________________
Correct... and yes you would think that they would fit them but there is a good reason why they don't,
Example the amount of "nuisance tripping" and faulty external circuits that people fit to these things they would be forever having the generators returned "faulty" under gtee.
_______________
Quote
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The only outstanding thing, (for me, anyway), is what to do at the generator, with the earth wire in the cable from the portable generator to the boat power supply input, (shore power connector, for want of a better description).

The answers seem to me to be either leave it where it is, or connect it to the neutral as it enters the generator.
_________________________
This is where it becomes difficult..
If you know the U.K 13amp sockets or the round industrial type three pin plugs & sockets then you would wire the "green/yellow earth" to the "earth pin on the plug.

BUT BUT I think you said you were buying a "foreign jobbi" and only has a two pin outlet. If this is correct and you are thinking of wiring the "earth" wire to the Neutral then this must be connected to the neutral BEFORE the RCCB to be absolutely clear
I mean on the generator socket NOT on the "output side of the RCCB.

I MAKE IT CLEAR I AM NOT AGREEING/ADVISING YOU SHOULD CONNECT THE EARTH TO THE NEUTRAL AT ANY POINT AS I AM NOT THERE WITH YOU AND LOOKING AT THE INSTALLATION.

If an RCCB is being used, Personally and I am not advising this but Personally I would not connect the earth if a connection has not been provided for.That is not advice that is what i would do.but use RCCB and keep everyone away from the generator when it is running.

I don't post pictures Richard but I am surprised that someone has not photographed a sketch or a copy of a diagram and posted it
 
[ QUOTE ]
Correct.. The problem is the "loose" use of the word "earth"
For current to flow through you it has got to go somewhere for you to get a shock.
If it doesn't go anywhere you will become "LIVE" like the thing you are touching until you touch something else at the same time.(like the bird sitting on the power line.)


[/ QUOTE ]

It's hard to think of a word other than earth - I know what you mean.... the human might be touching a piece of metal which is bonded to the anode, or have their foot in the sea /forums/images/graemlins/smile.gif. I'm looking around the boat and finding it hard to see where a path for the current could be created, so, as Lemain has suggested, the risks of this happening seem slim, ( a suggestion which I have never doubted if you're reading David /forums/images/graemlins/smile.gif ).

[ QUOTE ]

This is where it becomes difficult..
If you know the U.K 13amp sockets or the round industrial type three pin plugs & sockets then you would wire the "green/yellow earth" to the "earth pin on the plug.

BUT BUT I think you said you were buying a "foreign jobbi" and only has a two pin outlet. If this is correct and you are thinking of wiring the "earth" wire to the Neutral then this must be connected to the neutral BEFORE the RCCB to be absolutely clear
I mean on the generator socket NOT on the "output side of the RCCB.

[/ QUOTE ]

So, if I chose to do this, the cable comes from the shore power socket on the boat, into an RCCB of some kind then, after the RCCB, but before the generator, is where the earth would be connected to neutral?? This would require an RCCB plug of some kind, then another short cable to the generator.

For those that might buy a UK model with a UK 3 pin socket, (which might be what I get I am told), what would be the thing to do with the earth wire .... particularly if leaving it connected to the earth pin on the plug showed no earth on the boat, (with a 3 neon lights thing).

Nearly there - I think

Thanks again

Richard
 
I live in a 2 pin plug region .....

And yes it is a concern that many sockets are not earthed out .... domestic etc. But they are changing to the 2 pin and side contact type ... where the plug has metal strips at side to earth out.
Generators normally have that 2 pin and strip contact plug / socket combo. Most gennys also have the casing earth with thumbscrew for attaching earthing strap to.

Now I find the threads on this subject frustrating - and this one doubly so - because there are posts here that INSIST they are thye only onesd who know the real truth !

My opinion, and I am not an electrician, but base it on reading the genny book and what I feel is logic ...

The genny has earth connection that is supposed to be grounded out by stake in ground etc. So here we have connection that can be wire to sea ... The sockets on the genny are already earthed - so any plug into it should be 3 wire connected to give continuity. An RCD - I prefer the plug in type bewteen socket and plug .... should be fitted.

I don't like bonding to hull points .... (I know - many of you will cry I'm a fool ..... but I don't believe in creating a path that is not there normally - which in effect you do if you bond to hull, giving you extra concerns to deal with ! ... ).

As I see it .... and you can shout / scream / call me all the idiot names you can think of .... but as long as continuity is maintained and a path to earth is provided then I think it's OK. I'm a great believer in following the indications of the genny / appliance manufacturer ....

Now to the confession ..... I have both a 800W and a 3.4KW genny .... both have earth connections .... both actually are used without earthing out ..... OK not on board yet ... (the 3.4KW job is actually my house emergency genny .... the 800W job is my portable power around the estate etc. and will be used on board at times.
I will be making up the earth to sea connection before next seasons use ........

I think it funny - that people have been using gennys for years ... without argument - since the introduction of cheapo chinese jobs on market and more people having them - the confusion starts ..........
 
Quote
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For those that might buy a UK model with a UK 3 pin socket, (which might be what I get I am told), what would be the thing to do with the earth wire .... particularly if leaving it connected to the earth pin on the plug showed no earth on the boat, (with a 3 neon lights thing)
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IF it has a 3pin socket you would plug your BOAT "shore lead " into the genny WITH AN RCCB as you would plug any "extension lead" into a socket at home.

Remember your boat lead is just that "an extension lead" from your consumer unit/control panel to connect to an "incoming supply" the incoming supply is in your case your genny.

The fact that you THINK the "earth" wire doesn't go anywhere is because you have the stand alone generator not going anywhere. this is why I said I would only "Earth/ground" my genny if my boat was out of the water.

This is why I suggest you treat the generator with respect because it (unlikely) may get a fault which causes the Case to become "LIVE"
 
Re: I live in a 2 pin plug region .....

Quote
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Now I find the threads on this subject frustrating - and this one doubly so - because there are posts here that INSIST they are thye only onesd who know the real truth !
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bit strong to say Imho, you should allow for the fact that like all posts /text msg ect.
what the person is trying to say when writing and what the other person reads can be to different things. its called misunderstanding(for want of a better word)

All are looking at Safety on board.

Its very difficult to say that putting an "Earth to sea" from the genny frame /case will not cause a hazard should a fault occur causing the lead to become "LIVE" (I hate that word) with respect to swimmers etc.
Ok an Insulated cable attached to a metal plate/lump and dropped to the sea bed and hoping the plate/lump is not insulated from "ground" by weed etc would be best
but not very practical.
 
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