Non VW = electrical safety when using a generator

[ghost123uk]

I have just spent ages on Google researching this, and I am confused, so I thought, as "we" have a huge pool of knowledge on here, it might be worth asking.

The generator in question is not your usual camping set up (as if I would !! ) but is used to power some equipment used by a friend and I, in a wooded area.

We would like to use a circuit breaker of some sort, but not sure how to go about it, especially with regard to the fact that the generator is not "earthed" in the way a normal mains supply is. I know I could fit an "earth rod" to it, but not sure if that is sufficient to make a normal earth leakage circuit breaker work properly, I suspect not.

Does anyone on here (that really knows, i.e. not guessing, as this IS a safety issue) care to input any info?

[tonytech]

I agree its a confusing issue. So I'll bow to anyone with better knowledge.

I've used generators to power outdoor Sound and Light shows.
If the generator is isolated from the earth, then you can only get a shock touching both live and neutral. As the current wont have a path back to the generator through the ground.
However it is almost impossible to reliably isolate a generator. even moisture can provide a path.

I've always used RCD circuit breakers (what most folk call earth leakage breakers)
RCD breakers trip when the DIFFERENCE in current flowing in the LIVE and NEUTRAL exceeds 30mA.

T

[Oldiebut goodie]

I am certain that years ago when I used a new Honda generator the guff said to use an earth spike and so I did when using it on a foreshore.
But - this says to link the neutral and earth etc. but recommends not doing it. (from justgenerators)

"I have bought a generator, and I am concerned about safety. Can I use a personal power breaker?

The generator is configured differently to the mains supply. The generator has a ‘floating earth’, whilst the mains has an earthed neutral. Whereas it is definitely recommended to use a personal power breaker (RCD) from the mains, for the majority of cases, it is not necessary to use one with a generator. Personal power breakers are designed to operate from the mains. If one is to be used with a generator, then it is necessary to modify the generator so that it is configured in the same way as the mains. This is a relatively simple modification for a qualified electrician involving adding a link wire from the neutral terminal to the earth terminal. However, once the generator has been modified, it is necessary to then always use a personal power breaker and to also always use an earth spike, which connects between the generator frame and the ground. Since this is difficult to ensure, it is generally recommended not to modify the generator."

I must admit that since virtually all electric tools that we use now are double insulated ones with no earth provision I have never used one again. Perusal of Honda's safety instructions leaves one none the wiser as to best practice as they are all fitted with an earthing terminal on the engine casing with no reference to earthing whatsoever!
No further forward really. My thoughts are that you are not going to be able to guarantee the efficacy of your earth where the soil may well be dry - thinking back to the days of crystal sets and the lengths that we used to go to to achieve a good earth. Tins of sal ammoniac, peeing on the earth etc!

[Mocki]

When used to operate Amateur radio field days with generators we always used earth spikes , more to cut down on interference than anything else, we found you needed a earth rod that was at least 1 meter long into the ground at least 75cm ( as were mostly out on the salt marshes this wasn't hard to achieve , but inland , with tree roots wouldn't be as easy !
Don't answer the question I know, but it odd proove the point that the earth rod was working, we could hear it and see it on the signal meters

[busbuddy]

The generator is configured differently to the mains supply. The generator has a ‘floating earth’, whilst the mains has an earthed neutral. Whereas it is definitely recommended to use a personal power breaker (RCD) from the mains, for the majority of cases, it is not necessary to use one with a generator. Personal power breakers are designed to operate from the mains. If one is to be used with a generator, then it is necessary to modify the generator so that it is configured in the same way as the mains. This is a relatively simple modification for a qualified electrician involving adding a link wire from the neutral terminal to the earth terminal. However, once the generator has been modified, it is necessary to then always use a personal power breaker and to also always use an earth spike, which connects between the generator frame and the ground. Since this is difficult to ensure, it is generally recommended not to modify the generator."

just a thought on that........ with generators plugged into a caravan running through the modern onboard rcd systems, surely the rcd must still work ? or they would have warnings on the caravan and generator stating such

and onboard motorhome ones come to that


when i used a generator i always had a plug-in rcd in the socket on the generator and then plugged anything else into that

[Oldiebut goodie]

Earth provided how?
From what I can see with a limited search of various generator datasheets none of them mention earthing other than a view of the earth connection point provided on the engine/chassis.
From my understanding of rcds (poor at best ) you can still have potential on a wire with a single pole rcd after actuation therefore an earthed neutral would be considered essential in that scenario. (therefore use double pole rcds only?)
Over to hands on electricians with far more practical experience.

[Jeff J]

If you are talking about some form of home made generator you may find useful info in the links to the IET site & others on here http://www.diynot.com/diy/threads/using ... st-3066764" onclick="window.open(this.href);return false;

[DiscoDave]

Generally speaking generators have the earth pin on the socket connected to it's own frame. From this you are supposed to put a rod in the ground, this would in theory complete the circuit of there was an rather fault. Personally I wouldn't trust the theory on a generator.

If you are wanting to use an RCD (why wouldn't you?) you will find that it won't work when the test button is pressed and as such won't work properly or at all in the even of a fault - even with an earth rod.

If this generator is powering a permanent installation, or you intend to use it with a portacabin or similar and the generator is not likely to be moved much then I would recommend using an earth rod at the generator and at the consumer unit in your installation.

If it's powering an extension lead then what I've described above won,t be of much use. In which case I would recomend a modified RCD lead, basically a short extension lead with an inline rcd in the middle. At the plug end link neutral and earth (must be before the RCD).

Before using either set up you must test using a proper test meter, the tripping times of the RCD at 1x rated current (usually 30mA) and 5 X rated current. At 5x it should trip within 40mS.

[busbuddy]

Earth provided how?

i wasn't saying you were wrong,

i was just thinking... with the amount of people using expensive whisper generators plugged into big modern caravans/motorhomes with ultra posh rcd units that there would be more warning info known about their use in the leisure world
to be honest i have never thought about it before, as i said i used a plug-in rcd without a second thought i'm sure we have all seen generators in use.....markets, building sites, campsites, shows, etc but who has seen any with an earth spike?
we have been with people at places like santa pod who are using rented 3kva generators and i've never known anyone to use an earth spike

is it just ignorance on my part or does nobody bother with an earth spike as its a 'will never happen to me scenario' , seems odd that the generator suppliers would not give better warnings and the dangers more spoken about on caravan forums at the very least

any reference about generators is usually size, noise, weight,

[ghost123uk]

Well thanks for the input folks, it is confusing isn't it.

I can say that, yes we are using a long cable from genny to workplace. We had fitted a proper wall mounted consumer unit inside this workplace, but as mentioned above, it didn't work.

Re earth spikes, again, as mentioned by folk above, getting a decent, reliable "earth" at both ends is not feasible imho. The use of earth rods, whilst seemingly catered for on some generators, is it seems hardly ever used in the real world.

As "we" are more concerned with electric shock dangers from dampness, or current leaking to "touchable" parts, I am starting to err on the "genny is isolated" theory Tony mentions. I wonder if a simple measure of AC current, referenced to a temporary earth rod might show interesting (low) readings?

[Oldiebut goodie]

I operated a safety boat for welders that were working on the top of 60ft sheet piles that were upright ready to be dropped during the building of quaysides in the river - the welding generator was on a floating pontoon and we would get shocks through our rubber boots when on it! I haven't a clue as how earthing was/would be effected there, I think that there was none.

I suspect that your practical solution would be to tie the neutral to earth at the generator and use the spike as mentioned earlier.
(sounds like you have an illicit still out in the backwoods producing moonshine! )

[ghost123uk]

I have just had a thought, based on what you folk have mentioned, in particular DiscoDave.

The generator is housed in a waterproof wood and roofing felt structure, in a corner of this, let's call it an allotment, because that is the nearest description that fits. A heavy double insulated cable runs from there, about 25 yards, to a wooden, let's call it a shed, because that is the nearest description that fits. In this shed is the "consumer unit". When I said above that it didn't work, I should have said that actually it trips as soon as any load is put on it. It has done so since we installed all this, in a totally dry, hot part of the summer (so it's not damp causing it). Perhaps, as Dave says, the long cable and possible imbalances between live and neutral cause it to trip?

Next plan = temporarily fit a simple RCD at the generator end and test that out.

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Asides=

OBG, it's nothing as exciting as a still, it's a workshop / "man shed" with a few simple tools, lighting and a sound system for those chilled out nights around the camp fire (though we did have a pretty full on Halloween party / bonfire / fireworks / BBQ etc last Saturday night )

Mind you, I recently set up a full solar charging system, leisure battery, inverter and a half decent car amp down there, to provide power for lights and music, to cater for times when only a modest amount is needed.

[tonytech]

What sort of consumer unit?
I'm assuming you mean the RCD trips rather than the individual circuit breakers.
Is it is a split board, with a "socket / ring main" side and a "Lighting "side?
Its important to get the Neutrals on the right bus. putting a socket neutral in the lighting bus or the other way around will cause a trip.


T

[ghost123uk]

What sort of consumer unit?
I'm assuming you mean the RCD trips rather than the individual circuit breakers.
Is it is a split board, with a "socket / ring main" side and a "Lighting "side?
Its important to get the Neutrals on the right bus. putting a socket neutral in the lighting bus or the other way around will cause a trip.

Ta for the input. It is over 6 months since it was fitted, (then bypassed ) so I will have to nip down there and look in the cupboard to I.D. it's type etc. iirc it was a simple (though "in-line" rather than socketed) RCD thing.