Portable Genny - Worth bothering with?

Taking nothing away from what others have said. I know nowt about lectricery. We went years without a little genny and thought it was fine. Then I sort of acquired one, little 4 stroke Honda thingy. Just plugged it into the boats shore power. Now, it dont like running the immersion water heater, so switch that off. It wont run a microwave. Wrong sin waves or summat. But it means we can use the boat all year. Dont need marinas and keeps batteries charged for the diesel hot air heating. I'd be careful of running lap tops directly off it. But through a 12V charger, from the boat. No problem.

Anyway ours works a treat, for those winter moments. Dont expect it to compete with the national grid though.
 
I support Lemain here .... and disagree with the wire overboard ..

Why ?

I have similar genny - a Wolf 800 ... it too says ground out to a metal rod in the ground. It too has the earth wire visible chassis to earth connection in socket etc.

If you dangle a wire overboard - you a) lose the RCD cover by circumventing its mA detection ... b) you are likely to create a potential that could prove lethal to any swimmers nearby ... c) or a potential to increase anodic . cathidic action on your boat ...

Check out A. Garrods Book on Electrical Wiring / systems on boats ... he gives very illustrations of effects of mains wiring - which in effect using the genny is ...

My advise - connect genny same as a shore power lead ..... nothing else. That is told to me by an electrician after I quizzed him on this subject when I got my genny ... (I have a small portable and also a larger 3.5KW job ... )
 
[ QUOTE ]
My advise - connect genny same as a shore power lead

[/ QUOTE ]

I agree but be aware that the neutral and earth are connected together at the shore power substation so IMO the neutral and the earth should be connected at the generator.

[ QUOTE ]
Check out A. Garrods Book on Electrical Wiring / systems on boats

[/ QUOTE ]

I dont think I have that book but I will get a copy and check it out.

[ QUOTE ]
If you dangle a wire overboard - you a) lose the RCD cover by circumventing its mA detection

[/ QUOTE ]

As covered in the discussion with Lemain IMO the only way the mA differance can occur is a leakage back to the neutral via the earth.

[ QUOTE ]
you are likely to create a potential that could prove lethal to any swimmers nearby

[/ QUOTE ]

I dont understand the mechisum of this.

[ QUOTE ]
or a potential to increase anodic . cathidic action on your boat

[/ QUOTE ]

Only possible if earth of generator is also connected to the earth of the shore power connection without a galvanic isolator.

All of cause IMHO
 
[ QUOTE ]
Only possible if earth of generator is also connected to the earth of the shore power connection without a galvanic isolator.

[/ QUOTE ]While I don't want to get into giving people wiring advice I am monitoring these threads with interest and will point out that galvanic isolators are not some kind of magic that will necessarily prevent any or all galvanic action. At best they are not a perfect or complete solution to the problem that they are trying to overcome. At worst, they are useless.
 
[ QUOTE ]
My advise - connect genny same as a shore power lead

[/ QUOTE ] In which case, if there is not an isolating transformer on the boat, the genny earth will be connected to the boat's earth, which in turn will be earthed to water. So adding or subtracting another earth to the genny frame will make no difference - assuming that the frame is connected to its earth line!

Whether the genny earth/frame is connected to one of its outputs to create a nominal neutral is another point to be checked.
 
A.Garrods book is IMHO an excellent book as it gives plenty of illustrations and explanations ........ it is simply put for even me to understand !

The point about the swimmer is made clear and is one that also was made in PBO magazine some time ago when Earthing / mains installations were being featured. It all revolved around how to earth out the boat ... and various methods employed. The book and the PBO article showed the consequences of a fault and power diverting to earth.
RCD's are dependent on the residual current measurement and any action that alters / circumvents that will render the RCD inoperative.

Here we will definitely have cries of SHAME SHAME SHAME ... I do not earth out my 12V nor my 240 to any boat structure ... for very good reason - I do not have anodic or cathodic action prevailing on my boat. If I was to start earthing out to anodes etc. then I would have to start re-wiring and sorting out various protection items to then bring my boat back to non-eletrolytic state ... My earths are provided by shore installations - yes against many experts advise ... but in-line with electrician advise I had when making the decision.

Back to the real thread of whether the genny is worth it on board - I would expect that the charger system on board will not like the wave form of AC produced by this genny .... I have found that with cheap portable gennys that the cheapest charger possible is best ... as then they have non-computerised step-down and no fancy controller inside to prove problem. My cheapo Halfords non-float charger ... cost about a tenner ... works happily of the Wolf 800 ... but my clever float / boost charger does not. My cheapo Bosch chrager also works well of it ...
With two cheapo chargers ... even more if you have more batterys - the genny will run charging for both / more batterys ..
 
I dont understand what you are saying Sir, you have NO earth apart from shore power (hopefully) supplied ? and you have no isolation transformer (I presume?).
What happens if the marina earth does not function, for example, them, or your cord.... ?
Where is YOUR protection ?
RCD´s are not infallible either, You cannot rely on them as your main protection.
At the end of the day it is enteirely up to you.

As for modified sinewave gennys, the Problem with these, is the running of inductive loads and harmonics. Many cheapo chargers are inductive. hmmmmm.
I think you are living a fairly risky life, but again, up to you..
Be safe.
 
Earthing can be complex but also depends on the type of boat and equipment used.

My yacht is a steel hull and deck and as such has its anodes bolted to studs welded to the hull and thus earth the hull and deck to the sea water with no other connection. The hand rails and other stainless fitings also bolted / welded to the hull os also electrically connected.

On a glass fibre or wooden different conditions as the stainless deck fittiing may not be electrically connected

With a shore power connection the earth should be connected to the hull and infact big ship regulations insist on this. This earthing can cause problems with the wastage of anodes due to there possible connection to the marine structure and other boats. One way to overcone this is with a galvanic isolator. The other is with an isolation transformer.

My plan for my shore power instalation is in this form with RCD in the shorepower line and the earth line AC connected through a GI to the marina power so if there is an earth fault my RCD will trip if the marina RCD does not pick up the fault. The leakage current returning down the earth connection causing a differance in current in the Line and neutral connections.

There is the possibility of a swap in the line / neutral connection at an unknown shore power connection and that is why I have included 1 neon lights in the shore power feen to indicate faulty connection and faulty shore power earth connection.

Now with my onboard diesel driven mains alternator (which will have a true sign wave output ) and my inverter (which may or maynot have a true sign wave output but is not important for this discussion) will also have seperate RCD's in circuit. The selection of which one will be by a single 2 pole 4 position switch (switching line and neutral) so only one can feed the internal mains grid at a time. Now I contend ,and seems to have a number of supporters on the thread started by another forum member on this subject, that the neutral of the inverter and generator must also be connected to the earth to provide an alternate path to any leakage current to flow so that the RCD's can operate correctly.

I will have no connection at all between my 12 VDC and the hull to prevent any possibility of an impressed galvanic current within the hull, engine and generator 12VDC totally isolated

Now after having a shock from a honda suitcase generator without the RCD tripping as discussed with Lemain I consider the best practice would be to also earth the neutral connection as above. Now if this is best done with hanging a wire over the side into the sea could be debatable but IMO for an RCD to work there must be this earth path for the RCD to function.

99 times out of a 100 there will be no problem and no danger but the s**t will only hit the fan when an earth fault occures which could be when using a mains power tool on deck while sailing and again if the weather is not bad no problem but take a green one over the deck and the condition changes to a potential to electrocution.
 
[ QUOTE ]
As for modified sine wave gennys, the Problem with these, ....

[/ QUOTE ]I've not come across those. Do you have an example?
[ QUOTE ]
RCD´s are not infallible either, You cannot rely on them as your main protection.

[/ QUOTE ]The main protection is always insulation to prevent people from touching live things.
 
You are of course correct in the comments about protection ...

But it also has to be said right or wrong ... that many do not post on this sort of thread ... why ? Because thousands of boats go around with similar to my set-up ... mains power via garage / shed / all-in camping systems .... don't have all the gear that is posted about.

No-one said my set-up is correct ... but also no-one actually says one set-up is either ... all the books I have and I have about 4 on the subject all advocate different set-ups ... one in fact advocates exactly the swimmer electrocution method !! that Garrod illustrates .....
 
[ QUOTE ]
The main protection is always insulation to prevent people from touching live things.

[/ QUOTE ] Agreed.

But just to be really pedantic, 'touching things live relative to whatever else they are in contact with'.

Worth bearing in mind when you're planning independent generator or isolation transformer installations, when your most likely contact will be with the frame of the machine itself.
 
Sure. If there is a reasonable chance that a conductor could give an electric shock then it needs to be insulated or a cover put in front so fingers, tools etc., can't touch it. If a conductor is touchable in normal use by its very nature (e.g. a frame, handle or switch) then you have to make sure that it won't become live in such a way that it could give a shock - and that means live with respect to something - usually earth. Earths and RCDs only do something in the fault condition - ideally an earth connection will carry no current even though it must be capable of drawing enough current to blow a main fuse and ideally an RCD will never trip in anger.
 
Well, there's an interesting corrolary to the point I made above. That is, if neither output line is connected to 'the frame' , or earth, the only way you'll get a shock is if you touch both lines simultaneously. Which is why some people argue that you shouldn't take a line to earth . . . because then you only have to touch the live to get a shock.

An interesting point of view, reasonable if you don't have an RCD in the genny.
 
Yes, that's the 'floating' supply argument. Building sites have been doing that with isolating transformers for years, though I don't know if it is current UK practice today.
 
[ QUOTE ]
Building sites have been doing that with isolating transformers for years,

[/ QUOTE ]

Yes but the centre tap of the secondary of the isolating transformer is connected to goround so the max voltage possible relative groung is 55 VAC reducing the effect of any shock .
 
[/ QUOTE ]Yes but the centre tap of the secondary of the isolating transformer is connected to goround so the max voltage possible relative groung is 55 VAC reducing the effect of any shock .

[/ QUOTE ]55V in the US, but in Europe it is 110V max. When the transformer is centre-tapped and connected to local earth, it is called 'split phase'. I think it is (or was) more common in the UK to have a floating supply. The idea of split phase is to halve the maximum voltage; the idea of fully floating is to reduce the chance of a shock to almost zero as there is no earth return. Floating systems become impracticable when they get larger as a leak or fault somewhere tends to tie the supply to earth. Split phase systems are a real nuisance in marinas as the N is a supply rail - you have to have an on board isolating transformer - there is no practical alternative. I haven't seen it used in marinas for over 30 years but it used to be quite common in France.
 
55 will kill you just as easy as 110 or 240 David. A lot depends on the route the current takes through your body.
Its volts that jolts n Mils that kills.

My apologies David, it wasnt you that posted that, it is to the poster.. Joe
 
I agree that is why RCD's have become more common with a trip point of 30 mA.

But as I keep saying the supply must be commected correctly and I think you also stated that the neutral of the supply must to connected to earth to allow this leakage current to flow and cause the RCD to trip.
 
Interesting

I did a google and cane up with this referance

web page

It quotes 240VAC input 110 VAC secondary centre tapped to earth

It also states Built to conform to BS3535

Now I dont know exactly what BS3535 states but these people in the UK seem to have some very interesting products when anyone wishes to use UK appliances in the US and US appliances in the UK
 
You must log in or register to reply here.

Other threads that may be of interest

Skipper Felice
Optimisation of the battery charger infrastructure
Replies
1
Views
143
PaulRainbow
PaulRainbow
P
Adding fuses to my batteries
2 3 4
Replies
61
Views
2K
AngusMcDoon
AngusMcDoon

Share this page

Top