Portable genny - works OK - but can I use it??

[Anonymous]

I don't bring the shore earth on board. It causes big problems with corrosion (electrolysis) and galvanic isolators are an incomplete and imperfect answer. Since I am connected to shore power 24/7 in the winter, I don't want that.

I never said that the generator/invertor must be earthed - it has all been discussed earlier in the thread. But yes, if you earth the invertor or generator then it is no longer floating.

 

[Richard10002]

[ QUOTE ]
I don't bring the shore earth on board. It causes big problems with corrosion (electrolysis) and galvanic isolators are an incomplete and imperfect answer. Since I am connected to shore power 24/7 in the winter, I don't want that.

I never said that the generator/invertor must be earthed - it has all been discussed earlier in the thread.

[/ QUOTE ]

I agree that you didnt say anything of the sort, and that it has been discussed, "ad nauseum", I guess.

Presumably you disconnect the earth wire from your shore cable, and leave it at that. A strange concept, but I have some faith in your knowledge and judgement, and see that it removes the Galvanic corrosion issue.

I may have missed something in the various presentations, but how does the RCD work without an earth?

 

[Richard10002]

[ QUOTE ]
Try not to be tempted by your natural curiosity to touch live wires /forums/images/graemlins/wink.gif

[/ QUOTE ]

Just got this - to see if you're right and it doesnt shock/kill me, rather than checking its' live....

again - dont worry.

R

 

[Anonymous]

It was just a little joke, really /forums/images/graemlins/smile.gif

 

[Richard10002]

I know /forums/images/graemlins/laugh.gif but you never know - and it took me a while.

 

[Anonymous]

Periodically I do check with a old fashioned analogue meter that when I measure between L or N and true earth (i.e. the internal bonding to the anodes and stanchions) that the meter reads zero. If it doesn't then you have lost the integrity of the floating supply. If that happens the first thing you want to do is get the earth back on again, where it was 'supposed' to be then hunt for the problem (remembering that we are liveaboards and turning off the mains has consequences).

 

[orizaba]

to lemain re your previous answer

"Presumably you disconnect the earth wire from your shore cable, and leave it at that. A strange concept, but I have some faith in your knowledge and judgement, and see that it removes the Galvanic corrosion issue."

i assume that by disconnecting the earth you mean the boat is in isolation from stray currents etc,and you have no earths to any part of the bonding system etc on the boat so all is self contained.
i have to say i am slightly unclear about this concept, the way i read your way of doing it is,mains cable coming onboard with the earth disconnected,into a distribution box, using just live and neutral then out the distribution box going thru an rcd and into your mains circuit,
am i reading this right or have i missed something

 

[Anonymous]

That's right but of course on shore power the N is tied, somewhere, to local E so it isn't really true to say that the system is floating. The problem with bringing the E on board is knowing what to connect it to....you dare not connect it to seawater earth which should be connected to things like your stanchions, so what do you connect it to?

 

[billskip]

Surly Lemain you have two completly different circuits not connected to each other
If you have 12v and 240 v. The earth from the shore power is connected to all the 240v stuff.

the fact that you are afloat , and you put the genny on the deck is is no different with the earth connection ,it is connected to the 240v circuit ONLY.

The earth must be connected back to the genny chassis but must NOT be connected to the neut on the output side of the rcd.

The genny as said before should have a 3 pin 240 v outlet .

I dont realy understand why R-F.M44 has a problem because if his shore power circuit has been installed correctly all he has to do is plug his shore power into his genny.

The question arose for him because he has a light saying "reverse polarity " and he asumes this is due to earth connection.

 

[Anonymous]

[ QUOTE ]
I dont realy understand why R-F.M44 has a problem because if his shore power circuit has been installed correctly all he has to do is plug his shore power into his genny.

[/ QUOTE ]As I said to him, he does not have a problem if he plugs his genny into his shore power (which is what he says he is now doing). Why would he want to plug his shore power into his genny? It would blow up.

I think your other comments have been thrashed out ad nauseam in this thread.

 

[Guest]

"Surly Lemain you have two completly different circuits not connected to each other
If you have 12v and 240 v. The earth from the shore power is connected to all the 240v stuff." .....

If you do as some books say - you will ground out 12v to same hull point as 240V ... so in fact you would not have 2 completely 100% separate circuits ... OK L and N are separate - but earth is not.

This is one reason I am against bonding this way ... for me they are to be TOTALLY 100% segregated.

 

[billskip]

Quote

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As I said to him, he does not have a problem if he plugs his genny into his shore power (which is what he says he is now doing). Why would he want to plug his shore power into his genny? It would blow up.
-------
??????

A Genny as you Know is a stand alone Item. One does not "plug a genny into things "
one "plugs" things into the genny"

A genny has a "socket" his shore power lead on his boat has a "plug" therefor he "plugs" his shore power lead into his genny.

If you are trying to suggest that I am saying one plugs the shore power supply from the pontoon into his genny, you are incorrect.

you cant "plug" the shore power supply fron the pontoon into the genny because the shore power line has a "socket" and the genny has a "socket" and you well know you cant "plug" a "socket" into a "socket"

 

[rogerthebodger]

Yes you need this anyway even if you dont connect neutral and earth for the generator / invertor. I currently have a 2 pole switch but the plot thickens

I am going to make referances to earth point and earth line to try to mane my discussin as clear as possible (I hope I do)

Earth point is the point the earth line is connected to the earth via a spike or connection to the sea through an earthing plate.

This earth line / earth point / neutral connection should be done at the power supply as indicated in several books and in several referances (including the book indicated by sbc (nigel) C wing and calder should NOT be connected at the boat.

This is refered to by the shock experances you a swimmer near the boat in question

Now what is the supply point.
with a generator or inverter the unit is the supply point so the the neutral nust be connected to the earth line and the earth point (phical earth connection)

Now with shore power the earth point is at the marina substation / distribution box. so no earth point connection should be made on the boat but the earth line from the shore power lead must be connected to the earth line on the boat.

All ok but is an isolation transformer is fitted this then becomes the supply point and the neutral of the transformer secondry must be connected to the boat earth point as well as the earth line. This makes the connection the same as the generator / invertor in effect all neutrals and earth point and eatrh line connected but still a 2 pole switch down streen of the earth / neutral connection.

Now with a shore power connection without an isolation transformer the neutral / earth line / earth point must not be connection so for my arrangenent and lost of others a 3 pole switch must be used the thitd pole used to connect the earth line and the earth point together only when the invertor or generator is selected and open when the shore power is selected thus disconnection the earth line from the earth point on the boat

Having been away in Durban the last 2 days (on busness no sailing /forums/images/graemlins/frown.gif ) I did get hold of Garrod's book and he does explain the problems but still got it wrong on one of his diagrams. And did explain the swimmer shock cause and the way to overcome it.

He also discussed the "to ground or not to ground" and shows a simple reverse polarity indicator which I have also included in the design of my system.

 

[cliff]

Just to confuse the issue a bit, I checked the wiring diagram for my Kipor 3000Ti and it appears the 240v output is isolated from the earth. ie the "neutral" on the AC side is not connected to the earth. The 240v recepticle earth connection is connected to the chassis and to the "earth" terminal on the casing which according to the manual should be connected to ground which I assume would be a ground spike if used on dry land or some form of earth plate (hung in the water) if used onboard the boat.

In my case I keep the 12v and 240v circuits seperate (no common "ground") and have a piece of sintered bronze (connected to a cable) which can be dropped over the side to provide an "earth" for the genny. No where does the 240v neutral or earth appear to connect with the boats 12v neg (or anodes) unless through the onboard invertor - must chack that out sometime.

Have I got it all wrong and should I be doing something else in relation to earthing?

As a point of interest the ELCBs / RCBs seem to work irrespective of whether or not I connect the genny earth (sintered bronze block) or not.
--------------------

"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>

 

[Anonymous]

[ QUOTE ]
Have I got it all wrong and should I be doing something else in relation to earthing?

[/ QUOTE ]It sounds fine to me. As a final sanity check, you might try putting an ac voltmeter (analogue) between your stanchions and your sintered plate to see that a bather getting out will not get a belt.

I don't know where the idea of electrocuting swimmers in the water came from (earlier this thead) but you certainly could kill someone getting out if their feet were in the sea and the grabbed hold of a live rail /forums/images/graemlins/shocked.gif

Digital voltmeters have such a high resistance that you can get a reading even when the leakage is trivial...the same is true of some analogues, but to a lesser extent.

 

[rogerthebodger]

[ QUOTE ]
I checked the wiring diagram for my Kipor 3000Ti and it appears the 240v output is isolated from the earth. ie the "neutral" on the AC side is not connected to the earth. The 240v recepticle earth connection is connected to the chassis and to the "earth" terminal on the casing

[/ QUOTE ]

That is the same as my honda suitcase generator from which I got a shock after droping the eatension leas in the sea with the RCD triping as described earlyer in the thread. I have now connected the earth and neutral at the generator to prevent this from happening and now if I drop the extension in the sea my RCD trips stright away.

[ QUOTE ]
As a point of interest the ELCBs / RCBs seem to work irrespective of whether or not I connect the genny earth (sintered bronze block) or not.

[/ QUOTE ]

I would be interested in how you tested that the RCD triped without the earth plate connected.

 

[jimbaerselman]

[ QUOTE ]
I checked the wiring diagram for my Kipor 3000Ti and it appears the 240v output is isolated from the earth. ie the "neutral" on the AC side is not connected to the earth.

[/ QUOTE ] I suggest a double check using a meter. Check for infinite resistance between earth socket output and each of the line outputs (while not running!). Then check the AC voltage between earth and each of the line inputs while running - should be nothing. If that's the case, I can't see what would cause a current differential in the RCD to trip it . . .

 

[cliff]

[ QUOTE ]
I would be interested in how you tested that the RCD triped without the earth plate connected.

[/ QUOTE ]Pressed the "Test" button /forums/images/graemlins/grin.gif
--------------------

"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>

 

[rogerthebodger]

That omly test the RCD is working by creating a connection across the line and neutral lines before and after the sencing coils.

As said before for a RCD to work ie greater than 30mA differance in line and neutral there must be an alternate path for the current to flow.

This is via the earth connection so no earth no current flow bypassing thr RCD so no trip.

Have a read of the electrics afloat book refered to by sbc