Earthing GMC Generator 850w
Submitted: Monday, Jul 02, 2007 at 12:23
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RiCeYWA
In the instruction manual it advises earthing the generator. Is this neccessary and what could happen if it wasnt earthed?
Cheers.
Reply By: Mark Taylor - Monday, Jul 02, 2007 at 13:37
Monday, Jul 02, 2007 at 13:37
This is a safety issue.. but with most appliances now being dual insulated it is not so important. For my GMC I bought a plug in safety switch. These simlpy compare the current flow between the active and neutral, and if there is a difference it shuts down the power.
With 240v, safety is an issue and the safety switch cost me almost as much as the $99 generator, but does give peice of mind at the
camp site.
Cheers
mark T
AnswerID:
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Follow Up By: disco1942 - Monday, Jul 02, 2007 at 16:07
Monday, Jul 02, 2007 at 16:07
Mark
I take it your "plug in safety switch" is an earth leakage breaker type. These work on power
grid applications where the neutral circuit is earthed back at the sub station. If you draw a little current off the active by contacting that active line then less current flows back via the neutral line to the sub station and it goes back through the earth system. This difference in current flowing in the active and neutral wires is what trips the switch. Unless you have your generator circuitry connected like the power
grid then the switch will not work as designed. In fact if you contact the active wiring you will not get much of a shock unless the neutral is connected to earth or you also you are touching the neutral circuit at the same time.
See also Mike Hardings reply in followup 1 to message 4.
PeterD
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Reply By: Robin Miller - Monday, Jul 02, 2007 at 13:39
Monday, Jul 02, 2007 at 13:39
Not necessary.
Robin Miller
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Reply By: Member -Signman - Monday, Jul 02, 2007 at 14:30
Monday, Jul 02, 2007 at 14:30
There is an OH&S issue here in NSW that all portable generators be earthed with a ground spike...
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Reply By: Member - Andrew (QLD) - Monday, Jul 02, 2007 at 15:29
Monday, Jul 02, 2007 at 15:29
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Follow Up By: Mike Harding - Monday, Jul 02, 2007 at 15:36
Monday, Jul 02, 2007 at 15:36
Get a bag for me too :)
Check the archives - I have written at least a couple of detailed posts on this very subject.
It is not necessary to earth a small generator in a
camping situation - indeed there is an argument that doing so actually makes things more dangerous.
Mike Harding
mike_harding@fastmail.fm
PS. Your ELCB (RCD) switch will not work if fault current cannot flow to earth.
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Follow Up By: RiCeYWA - Monday, Jul 02, 2007 at 16:04
Monday, Jul 02, 2007 at 16:04
Will the surge protector work with the gen not being earthed?
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Follow Up By: disco1942 - Monday, Jul 02, 2007 at 16:09
Monday, Jul 02, 2007 at 16:09
Yes its circuitry is just connected between the active and neutral wires.
PeterD
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Follow Up By: RiCeYWA - Monday, Jul 02, 2007 at 16:15
Monday, Jul 02, 2007 at 16:15
many thanks :D
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Follow Up By: Mike Harding - Monday, Jul 02, 2007 at 16:44
Monday, Jul 02, 2007 at 16:44
If there is no earth... where is any fault current going to flow in order to create an Active / Neutral imbalance?
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Follow Up By: Mike Harding - Monday, Jul 02, 2007 at 16:46
Monday, Jul 02, 2007 at 16:46
Some confusion PeterD - after reading your followup to another post I think we actually agree that an ELCB will _not_ work if the system has no earth connection?
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Follow Up By: RiCeYWA - Monday, Jul 02, 2007 at 17:29
Monday, Jul 02, 2007 at 17:29
So Mike is it your opinion that the surge protector will not work if the gen isnt earthed?
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Follow Up By: Mike Harding - Monday, Jul 02, 2007 at 17:37
Monday, Jul 02, 2007 at 17:37
Surge protectors, of the domestic kind, will not work full stop. I think it was this
forum I posted the maths of the energy capability of "surge protectors" to a year or so back - waste of money... unless you pay _lots_ of it :)
With small gens just be sure not to plug/unplug big loads when other things are connected and don't let them run out of fuel either. Expensive gens are better in this regard but NOT immune.
Mike Harding
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Follow Up By: RiCeYWA - Monday, Jul 02, 2007 at 17:45
Monday, Jul 02, 2007 at 17:45
Well seeings Ive already purchased one is it worth having it on there anyways?
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Follow Up By: Mike Harding - Monday, Jul 02, 2007 at 18:57
Monday, Jul 02, 2007 at 18:57
It won't do any harm... but the answer to your question is... no :)
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Follow Up By: RiCeYWA - Monday, Jul 02, 2007 at 19:08
Monday, Jul 02, 2007 at 19:08
So how do they get away with selling a product that doesnt do what its marketed to do.
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Follow Up By: Mike Harding - Monday, Jul 02, 2007 at 19:32
Monday, Jul 02, 2007 at 19:32
We do not live in a perfect world my friend - sometimes... you have to look after yourself out there....
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Reply By: RiCeYWA - Monday, Jul 02, 2007 at 15:46
Monday, Jul 02, 2007 at 15:46
Thanks for the replies.
I did try searching for topics on GMC generator and earthing but didnt find the info I needed.
I have purchased a Surge Shield so hopefully that will stop any appliances blowing up haha
Cheers.
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Follow Up By: Member -Dodger - Monday, Jul 02, 2007 at 16:24
Monday, Jul 02, 2007 at 16:24
But will not stop the Genny blowing up.
Mike's answer is the correct one.
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Follow Up By: RiCeYWA - Monday, Jul 02, 2007 at 16:29
Monday, Jul 02, 2007 at 16:29
Why would the genny blow up?
Im confused...
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Follow Up By: Mike Harding - Monday, Jul 02, 2007 at 16:57
Monday, Jul 02, 2007 at 16:57
_You're_ confused!? Join the club - _everyone_ on here is confused :)
This thread may help:
Site Link
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Follow Up By: RiCeYWA - Monday, Jul 02, 2007 at 17:28
Monday, Jul 02, 2007 at 17:28
OK I followed your link and read that thread now I have a migraine and I think its ok to run without the earth hahaha
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Follow Up By: Robin Miller - Monday, Jul 02, 2007 at 18:31
Monday, Jul 02, 2007 at 18:31
I wouldn't bother - its just another thing to plugin / get wet - and another possible connection to go wrong.
Robin Miller
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Follow Up By: Robin Miller - Monday, Jul 02, 2007 at 18:33
Monday, Jul 02, 2007 at 18:33
Now I'm confused - above reply was to be in relation to using surge protector , now that you have brought it.
Robin Miller
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Reply By: Gramps (NSW) - Monday, Jul 02, 2007 at 17:16
Monday, Jul 02, 2007 at 17:16
Why not just earth it and be done with it ?
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Follow Up By: RiCeYWA - Monday, Jul 02, 2007 at 17:30
Monday, Jul 02, 2007 at 17:30
Well I thought about that till someone mentioned that earthing it could make it more dangerous if the earth isnt a good one
Brain implosion in 3, 2, 1
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Follow Up By: Mike Harding - Monday, Jul 02, 2007 at 17:31
Monday, Jul 02, 2007 at 17:31
Because that's not a _good thing_ to do with a small gen in a
camping situation.
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Follow Up By: Gramps (NSW) - Monday, Jul 02, 2007 at 17:43
Monday, Jul 02, 2007 at 17:43
Bugga !!!! More bloody reading to do. Thanks :)))
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Reply By: Glenn WA - Monday, Jul 02, 2007 at 17:59
Monday, Jul 02, 2007 at 17:59
Maybe this will confuse things,
Your generator supplies only equiptment mounted on it, or appliances connected to the power supply.
Portable equiptment is either double insulated or contains an earth through the 3 pin plug top.
Non-current carrying metal parts ( fuel
tank, motor and housing ) are bonded to the generators frame and system so then the appliances are also bonded to the frame of the gen. ( if you don't have this then a ground electrode is needed ).
So then, rather than connecting a grounded earth electrode the generators frame will replace the ground electrode.
If your gen does'nt have RCD (residual current device) protection, then a portable RCD is advisable and will trip the dodgy equiptment if functioning correctly when 30 milli amps of current is detected.
Better through the safety switch than your body. IMHO.
Cheers, Glenn
AnswerID:
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Follow Up By: Mark Taylor - Monday, Jul 02, 2007 at 19:16
Monday, Jul 02, 2007 at 19:16
Well, I'm even more confused.
Not having had faulty gear my safety switch has not tripped .... except when the generator runs out of fuel and does a hi rev followed by coming to a halt. The safety switch then turns off and has to be reset when you refuel and start the generator.
Any clues gents?
Cheers
MT
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Follow Up By: Mike Harding - Monday, Jul 02, 2007 at 19:31
Monday, Jul 02, 2007 at 19:31
Yes.
I'd be interested to hear (be corrected by) from Electrical Engineers on this one...?
I had a ShopVac vacuum cleaner with which I could, reliably, trip
my home ELCB despite the fact that the ShopVac was double insulated and did not even _have_ an earth pin. What I believe was happening was that the sharp currents spikes produced during the on/off transistions of an inductive load were "fooling" the ELCB into believing there was a current imbalance between Active and Neutral - it's a tad more complicated but that is the nub... imo... anyone care to expand?
Mike Harding
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Follow Up By: Member - Mike DID - Monday, Jul 02, 2007 at 22:58
Monday, Jul 02, 2007 at 22:58
I think ELCBs also act as fast overcurrent trips.
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Reply By: Member - Norm C (QLD) - Monday, Jul 02, 2007 at 19:46
Monday, Jul 02, 2007 at 19:46
Mike Harding,
well up the page you commented that you should not let your gennie run out of fuel. I read into this that there are safety concerns with doing this.
Can you elaborate on this. I don't often do this, but it has been known to happen, and will again I suspect.
I've just upgraded from a 1KVa t a 2KVA, so have twice as much available power to worry about. But I suppose killed by a Mini Minor, or killed by a bus, you are still dead.
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Follow Up By: RiCeYWA - Monday, Jul 02, 2007 at 20:09
Monday, Jul 02, 2007 at 20:09
Im guessing when it runs out of fuel it leans out therefore causing the gen to give a power spike that could kill anything connected to it.
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Follow Up By: Mike Harding - Monday, Jul 02, 2007 at 20:24
Monday, Jul 02, 2007 at 20:24
Hi Norm
The problem is that during this period the gen is surging and the
feedback loop which tries to keep engine speed in context with electrical load gets very confused and, often, doesn't work, this results in high (and low) voltage surges - expensive gens are better in this regard than cheap ones but I wouldn't trust any of them.
Mike Harding
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Follow Up By: Member - Norm C (QLD) - Monday, Jul 02, 2007 at 21:00
Monday, Jul 02, 2007 at 21:00
Thanks for that Mike. Figured that might be the case. So if I'm out fishing with the wife, we are safe, but not someone who has snuck into our
camp site to pinch my battery charger.
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Follow Up By: Mike Harding - Monday, Jul 02, 2007 at 21:56
Monday, Jul 02, 2007 at 21:56
>So if I'm out fishing with the wife, we are safe
_I_ don't know Norm... you know your wife far better than I...! :)
Mike Harding
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Reply By: Member - Mike DID - Tuesday, Jul 03, 2007 at 10:09
Tuesday, Jul 03, 2007 at 10:09
If your generator is
well insulated from ground, then if you contact a single live wire no current can flow through your body. The whole system is basically "double-insulated". An ELCB will not trip.
If your generator is
well insulated from ground, you have an appliance with a metal case and there is a fault causing current to flow to the case, an ELCB will trip. Even if there is no electrocution
hazard, this may prevent a fire occurring.
If the generator has its Neutral connected to its chassis and the chassis is in good contact with ground, an ELCB will trip in a fault to ground.
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