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

[Richard10002]

[ QUOTE ]
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.

[/ QUOTE ]

Note quite my perception:

I think the earth was going "nowhere" on my previous genny because the 3 neon tester said there was no earth and, whichever way I connected live and neutral, the "wrong polarity" light came on.

After some discussion, this suggested, (to me), that there was no path along the earth wire for a fault leak to travel.... thus leaving any socket cases, or appliances, live... I believe.

If, (inside the generator), the earth wire is connected to something which provides a path, whether this could be the genny case/frame, or the neutral wire, or something else, my thinking is that the neon tester would sense an earth, and the polarity would show as correct, (unless the wires are connected the wrong way round). It would also provide the path for faulty leaks, thus leaving the socket cases etc. not live.

I accept that the genny case could become live if there was a fault, but at least the boat electrics wouldnt - if my thinking is correct.

Sorry to harp on - I guess a little knowledge and an inquisitive mind can be a PIA.

Richard

 

[Guest]

Re: I live in a 2 pin plug region .....

Sorry Bill ... but I stand by my post of saying that some posts insist they are the only ones who know ! Every time this subject comes up the same schools of advise tramp out.

As to electrocuting swimmers - I got shot down last thread that had anything to do with earthing out to sea and I mentioned the swimmer angle ...
As to having insulated wire - I would have insulated wire to stop any accident onboard where someone touches it before it's in water ... OK - someone will now say - it will only hurt if you provide a circuit .... if not then nothing will pass via your soft body ! Agreed but bare wire across deck ? No.

It doesn't need a block or plate in the water ... as long as enough bare wire length is exposed .. if you do want to maximise contact - then a plate is best.

Reminds me of ships (tankers) when moored for loading / discharging cargo ..... they bond the ship to jetty with a cable clamped to ships rail ... trouble is the cable used is too small a diameter as it has to be able to be man-handled easily - so is usually about 1/2" maximum diameter including insulation. The real cable needed to keep ship bonded I was always told in College should be over 2" diameter !!

So we have similar with our genny .... a decent earthed out frame etc. should need a good size cable to make sure all goes down it to ground ... but the wiring on the genny is a lot less and probably with high resistance ...

mmmmmmmm makes you think !!

 

[ChasB]

Re: I live in a 2 pin plug region .....

I would agree that an insulated wire down to a plate sounds the best way. A heavy plate too - you need a weight on the end after all to stop the wire drifting up!

But you still need an RCD don't you?

Let's suppose you have your earth and so the metal chassis of generator connected to the sea. A faulty connection develops in a metal cased heater you're using and a live wire in it touches the case. There should be sufficient connection to the sea to protect anyone touching the heater (unless, god forbid, they actually have a bare foot in the sea!), but without an RCD the whole circuit carries on working...

Unless... you connect the neutral to the earth...?

/forums/images/graemlins/confused.gif

At least I'm not alone in being confused by this. /forums/images/graemlins/grin.gif

 

[Anonymous]

While I won't get drawn back into the discussion about earthing, have you bought the Honda, yet, Richard? While I am fairly certain that the Honda is the best portable you can buy, and remember you need a quiet generator in an anchorage, why not get a yard to quote you for an installed diesel genset?

Ask for a price for around 4kVA and 6kVA - you don't want to run at more than 50% load for more than 30 mins or so. Having a diesel generator is bliss...and cheaper on fuel. We don't use it for the kettle (pointless waste of money as gas is miles cheaper) it powers everything else. If you ran a poll here in 'Liveaboard' asking diesel genset owners if they would choose an installed generator again, I'd bet that 90% would say yes. Albeit at a cost but an installed genset will add to your boat's value for certain.

 

[Guest]

Re: I live in a 2 pin plug region .....

I did say in my previous that I go for the plug in RCD ... same as you use for your lawnmower / power tool etc. at home ... that piggy-backs onto it.

 

[billskip]

Ok
so lets see if we apply a slightly different situation.

Lets say you were not interested in boats but instead in airplanes.

you go up in your airplane and you fire up your genny what do you "earth" the genny to then?

 

[Anonymous]

[ QUOTE ]
Ok
so lets see if we apply a slightly different situation.

Lets say you were not interested in boats but instead in airplanes.

you go up in your airplane and you fire up your genny what do you "earth" the genny to then?

[/ QUOTE ]That's easy, you leave it to your licenced engineer cos you're not allowed to work on your own plane /forums/images/graemlins/wink.gif (Unless you have a special category of C of A)

 

[Plomong]

[ QUOTE ]
I AM NOT THERE WITH YOU AND LOOKING AT THE INSTALLATION.


[/ QUOTE ]

That's why we cannot tell him what to do with his specific installation -- we don't know how it is laid out, and how his existing and his new genny are designed.

Some quick questions, now we seem to be discussing a specific installation:

1) Does the genny directly generate AC or is that done by an internal inverter from the DC the genny generates?

2) Does the new genny come with a manual that explains when and how to connect up to your tools or boat circuit? If so, do you have the manual on CD or know where to get it online?

[ QUOTE ]
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 ]

Maybe the diagram we need is one prepared by Richard showing his existing setup, and another showing the new genny internal arrangement. Is that possible?

If you run the generator (old or new) without earthing, then don't touch when running, as Lemain and someone else have stated clearly, and correctly. That configuration is the floating one I indicated you should steer away from if at all possible.

One final point: if your RCCB (we call them RCD here) is rated 30mA but has a power circuit rated at, for example, 25A, the downstream overload protector should be rated no more than the maximum RCD current -- in this case 25A. Otherwise in an overload situation your RCD may fail before the overload protection works, and you could be the overload!!!! Extreme, but could happen, especially if the overload protector rating is significantly higher than the RCD max current. Remember that not all faults are circuit to ground -- sometimes they can be between the two sides of the circuit (phase to neutral, or whatever you want to call them) and that won't trip the RCD. Your overload protector is then your only hope.

 

[ean_p]

Hi Lemain
Can you expand on the not wanting to run the genny for more than 50% load for more than 30 mins please?

regards

Ian p.

 

[Anonymous]

Generally generators are not rated for continuous duty at full load. There are two issues - the engine and the alternator. Surprisingly, the alternator is the main problem even though most of them are water-cooled and you'll find that they cut-out if you try to run them at full load for long. If they are always run very hot they fail earlier than alternators run at a more moderate temperature. We have a 6kVA, which is ideal as we have aircon. 4kVA is probably fine for most cruising couples.