generator earthing

[TJAGAIN]

does anyone know how to earth a genny on a fibreglass sailing boat? and what if any are the problems on earthing
the boat in question is a sea going vessel.

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[ongolo]

Hi there,

I have benn watching this post and nobody replied.

I am also puzzling whether or not to earth my 1.5kva generator on my steel boat.

It is not a priority yet, but I would install an earth leakage relay. But I am not quite sure how to do it best, because these litle honda generators (mine is) do not quite work the same as the mains with L,N. and earth.

However, having an unprotected generator running on a steel boat worries me a little.

On the other hand, most powertools have two wires only and are not protected anyway because these have insulated housings/casings.

In your case, check your tools and if they are two wire you will hardly run a risk on a fibre glass boat. That is my opinion and not an absolute fact.

regards ongolo


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[halcyon]

Have you fitted earth leakage or RCD, as the RCD does not use earth, it measures the difference between live and neutral, it does not bother were the current has gone.
In the early 90's one major manufacture was having bad corrossion with some gen sets. After sometime hunting round we found that there was a battery charger in the gen set to charge the engine starter battery. This was taken of winding in the gen set and rectified by a diode, neg was connected to neutral, if the gen set had been running isolated to the boat there would have been no problem. But we were using a main engine battery, thus boat dc neg was connected to mains neutral via the gen set. Which was intern connected to mains earth at the marina, which was connected to ground via earth spike, a pile by the boat was sunk in the ground, the water round the pile connected it to the boat's prop, which was bonded to the boat's dc neg, which was connected via the battery neg to the gen set dc engine starter which was connected to gen dc neg, which was connected to mains neutral completing the circuit. Thus you got corrosion of the props.
At that time we relied on the RCD protecting people on board, and isolated mains from boat dc, if you isolated mains you do not have a problem, if you do not you need to start spending money protecting from possible stray circuits.


Brian

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[ongolo]

Brian, that was one complicated fault/story. )

I will not normally have shore power unless I must weld.

As far as I can see, this Honda Generator has two 110V windings bridged together to make 220V. There is no Neutral to speak of, that is nothing like an earth to neutral connection or reference.

Therfore the sum of the current going out of the one end say AC (A) will be equal to the sum of the AC (B). No matter which way the current goes I think this holds true. I hope I am not in this part of the circuit one day, but since the two outputs will always carry the same current, what exactly could trigger a protection?

I know quite a bit of electronics, but I am not sure this time.

I would like to know your opinion on this again.

thanks ongolo

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[MainlySteam]

Every rule that I know of requires generators to be earthed - in a glass boat that would be to the existing ac earth or if that not already existing to the anode.

For generators with a floating neutral, as is common with small portable generators, for example (including the Honda ones), be aware that tests show that RCD's do not necessarily reliably work (tests have been associated with use of such generators on construction sites where I understand many ban their use).

John

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[alanporter]

Having read the replies to this post, and understanding very little about electricity, I need some advice also.
I have a Honda 2000 generator which I use on my sailboat and with my trailer (caravan). I do not connect it to earth and it seems to work just fine. Am I doing something wrong, unsafe ? I would value some qualified advice and an explanation, in simple, non technical language, on what I should be doing.
The AC system in my boat is not connected to ground as I always rely on the shorepower ground connection, which I test before plugging in.
Many thanks in advance.

<hr width=100% size=1>Alan Porter

 

[ongolo]

Hi Alan,

I am going to research this and poder a bit. Then I let you know. I am building a 25 - 50A battery charger today (converting two old ones) to be driven by my 1.5KVA Honda gen.

You do nothing wrong, but I think it all depends what type of insulation your tools have.

After all earth leakage protcts you only if you get a shock to earth or rather it will trip when an earhed device has a faulty short/connection/leakage to earth.

If you take with your right hand live and with your left hand neutral whilst wearing rubber boots, nothing will protect you.

Use your head and be carefull in the meantime.

sorry to be of no more help at the moment.

regards ongolo

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[Mollari]

A generator could share a common earth with the shore-power circuit with your live and neutral going through a three pole power selector switch and a R.C.D.

(The reason they banned them from some building sites is that some site workers were getting shocked through wet power tools and they had disabled or bypassed the R.C.D.)

I will be installing a 7 kva on my boat and linking my 240volt earths (genset and Shore) to the low voltage circuit earth through a galvanic isolator to protect my boat and others around me.

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[MainlySteam]

<<<The reason they banned them from some building sites is that some site workers were getting shocked through wet power tools and they had disabled or bypassed the R.C.D.>>>

While I have no doubt that use of a generator on a construction site without a RCD would normally require the operators removal from the site, the reason they are banned from many construction sites around the western world is because the neutral is often not bonded (and that is common on small portable generators such as the little Hondas, for example).

Even if an RCD is used on such generators, they are not deemed to be safe as the RCD's are claimed to not operate reliably in a floating neutral system - there are a number of government OSH agency tests that claim to demonstrate this to be so (a number of these results were available on the internet, particulary from industry testing in Canada, perhaps they remain so). OSH documents from around the world often quote that evidence exists that RCD's may not work correctly if the neutral is not bonded (those from WorkCover South Australia as just one example).

Many OSH documents also warn about the danger or likelihood of prohibition of floating neutral generators on construction sites (many of those documents are also available on the internet from both government agencies and non government industry organisations and advisers).

To the boaty bit - each to their own, but I would not regard them as safe on a boat except in the case of short term dockside powering of a single double insulated power tool.

John

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