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[Tonka.]

Maybe I am missing something here 

I have seen many gennies running on sites and pushing out 240v. Domestic 240v is earthed to ground for our safety.

I have never seen a genny with an earth spike. Do they need one? Is it dangerous not to use one?

Just wondering  

[Ghost]

The frame is the earth mate, it sits on the ground so thats the contact for the earth,


thats my excuse and I'm sticking to it. Lol

[Kevin Wood]

I would say you should have one. The protective earth conductor from the generator extends to any appliances connected to it, in order to ensure that contactable parts of the appliances are not able to rise to a dangerous voltage with respect to earth.

You are standing on the earth and so there is potentially a return path where current can flow (through you) in the event of a fault causing contactable parts to become live.

However, an earth stake in the ground will be a pretty high impedance earth so to ensure you are protected you should, in addition, use an RCD on the output of the generator.

I know people generally don't bother, and I have been guilty of this myself in the past.

In some respects, earthing is perhaps not as important as when using a mains supply as the output of the generator would be "floating" rather than with the neutral conductor tied to earth, meaning that you'd probably need a combination of faults to give rise to a dangerous condition. Having said that, there is always the chance, so the correct answer is an earth stake at the genny and an RCD on its' output.

Kevin

[Dishevelled Den]

I always use a stake when running the unit - no sense in taking a chance

[Tonka.]

An example:

A caravan and a generator.
The caravan is sat on rubber tyres, a rubber jockey wheel and rubber blocks under the steadies with no other contact with the ground.
The genny is connected to the caravan and is stood on anti-vibration rubber blocks without an earth to ground.

What would happen if an appliance developed a fault ?  :-/

[Jimbob]

An example:

A caravan and a generator.
The caravan is sat on rubber tyres, a rubber jockey wheel and rubber blocks under the steadies with no other contact with the ground.
The genny is connected to the caravan and is stood on anti-vibration rubber blocks without an earth to ground.

What would happen if an appliance developed a fault ?  :-/

in that instance, we can only hope the caravan explodes, or at least burns to the ground 

[Kevin Wood]

An example:

A caravan and a generator.
The caravan is sat on rubber tyres, a rubber jockey wheel and rubber blocks under the steadies with no other contact with the ground.
The genny is connected to the caravan and is stood on anti-vibration rubber blocks without an earth to ground.

What would happen if an appliance developed a fault ?  :-/

It's not so much just the physical ground to worry about in this case. There will be contactable conductive items in the caravan. Stainless steel sink? Taps? Window frames? There will be appliances in the caravan which require an earthed supply. These two must be bonded together to prevent the possibility of a dangerous voltage developing between them. I.e. You touch a tap and the toaster at the same time, a bit of carbon from a burnt fragment of toast shorts the live element to the case.

In this instance I would at a minimum ensure that the frame of the caravan is bonded to the mains earth within the caravan, but you should also use an earth stake at the generator in case the whole caravan becomes live.

Regarding using RCDs, I hesitated to say this earlier, for a reason that will become clear, but if you are using an RCD on the output of a domestic generator it will be much more effective if you connect the neutral output of the generator to earth before the RCD. The problem is, that the generator will then be much less safe if it were ever used without an RCD. :-/

Kevin

[Tonka.]

Thanks for all input 

[Debs.]

My Machine Mart Honda 4 stroke generator has a threaded hole in the engine end of the alternator-casing with a clear 'earthing' mark......I always use a copper-plated steel ground spike whenever I set up the generator; it only takes a minute and "better safe than sorry".

[Kevin Wood]

I did one of my amateur radio contests with a new group this year. A group who have a little more "will to win" than my local radio club and thus don't mess about.

This involved setting up a "portable station" on a hill, which must not be mains powered.

I ended up setting up the 40kVA trailer-mounted 3 phase generator which they had acquired from somewhere. It appeared to be adequate. 

Oh, and it came with an earth stake and an RCD on each phase.

Kevin

[redelitev6]

I did one of my amateur radio contests with a new group this year. A group who have a little more "will to win" than my local radio club and thus don't mess about.

This involved setting up a "portable station" on a hill, which must not be mains powered.

I ended up setting up the 40kVA trailer-mounted 3 phase generator which they had acquired from somewhere. It appeared to be adequate. 

Oh, and it came with an earth stake and an RCD on each phase.

Kevin

40 KVA+3 phase !! they really weren't messing about!

[Kevin Wood]

I did one of my amateur radio contests with a new group this year. A group who have a little more "will to win" than my local radio club and thus don't mess about.

This involved setting up a "portable station" on a hill, which must not be mains powered.

I ended up setting up the 40kVA trailer-mounted 3 phase generator which they had acquired from somewhere. It appeared to be adequate. 

Oh, and it came with an earth stake and an RCD on each phase.

Kevin

40 KVA+3 phase !! they really weren't messing about!

We were cooking on 3 table-top double  electric cooker rings instead of a crappy camping stove and it still didn't flinch.  8-)

Kevin

[hotel21]

When I used to set up our mobile incident offices ( converted London long haul coaches or blow up tents) complete with generator/alternator sets/lighting as well as radio/computer/fax etc facilities, we were told by the Techs that we MUST use an earth to ensure correct use of the kit.  It was normally a copper spike wedged under the tyre into the tarmac if a suitable 'earth' into earth was unavailable or out of reach.

[Marks DTM Calib]

Lol, well yes, a safety earth connection is a good move (note, placing it under a wheel in contact with the tarmac is a VERY poor earth to the point where its not worth bothering with unless its raining very hard! ) .

So, why does an earth give us such a level of protection.

Well, lets consider the mains setup to your house.....the neutral connection is nothing more than a remote earth (at the sub station). As a result, the live return is via 'earth' (the neutral) and is referenced to earth (the neutral). This also gives you an insight as to how a PME bond can work where the neutral earth is good enough to support your house earth (they connect the neutral to your earth block where the supply enters the building)

And hence we use the earth connection to apply a level of protection as it gives us the ability to earth say a metal box which houses the electrical kit....the earth connection does NOTHING more than this!. We do this because it means that the user accessable parts will be at the same potential to the 'earth' you are stood upon and hence (in theory), no current will pass through you!

This is proven by looking at appliances which do not utilise an earth connection, they are considered double insulted as theere is to leves of insulation between the potentialy dangerous supply voltage and the user accessable areas.

So, is an earth always required, no......if an appliance is double insulated then it wont need one (i.e. a modern drill, TV's etc), if it has an earth connection (and probably as a result has a metal case) , then one should be provided.

A generator with a metal frame, should be earthed (I note some small ones are fully enclosed in plastic).

So, its not a cut and dried answer in reality.....and the chances are that the earth spike you drive into the ground to support this will not be a great earth anyway.....but something may be better than nothing.

The saving grace for a generator is that the live outut is referenced to the neutral but the neutral is not earth connected.....whence the live is NOT referenced to the ground which you stand on.....its effectively an isolated supply and hence its 'more' safe than the house hold mains.