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Earthing GMC Generator 850w

Submitted: Monday, Jul 02, 2007 at 12:23

RiCeYWA

In the instruction manual it advises earthing the generator. Is this neccessary and what could happen if it wasnt earthed?

Cheers.
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ThreadID: 47317 Replies: 9
Views: 1767 FollowUps: 29
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AnswerID: 250302   Submitted: Monday, Jul 02, 2007 at 13:37

Mark Taylor replied:

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
Reply 1 of 9
FollowupID: 511474   Submitted: Monday, Jul 02, 2007 at 16:07

disco1942 posted:

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
FollowUp 1 of 1
AnswerID: 250303   Submitted: Monday, Jul 02, 2007 at 13:39

Robin Miller replied:

Not necessary.

Robin Miller
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Reply 2 of 9
AnswerID: 250305   Submitted: Monday, Jul 02, 2007 at 14:30

Member -Signman replied:

There is an OH&S issue here in NSW that all portable generators be earthed with a ground spike...
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Reply 3 of 9
AnswerID: 250311   Submitted: Monday, Jul 02, 2007 at 15:29

Member - Andrew (QLD) replied:



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Reply 4 of 9
FollowupID: 511468   Submitted: Monday, Jul 02, 2007 at 15:36

Mike Harding posted:

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.
FollowUp 1 of 12
FollowupID: 511472   Submitted: Monday, Jul 02, 2007 at 16:04

RiCeYWA posted:

Will the surge protector work with the gen not being earthed?
FollowUp 2 of 12
FollowupID: 511476   Submitted: Monday, Jul 02, 2007 at 16:09

disco1942 posted:

Yes its circuitry is just connected between the active and neutral wires.

PeterD
FollowUp 3 of 12
FollowupID: 511477   Submitted: Monday, Jul 02, 2007 at 16:15

RiCeYWA posted:

many thanks :D
FollowUp 4 of 12
FollowupID: 511482   Submitted: Monday, Jul 02, 2007 at 16:44

Mike Harding posted:

If there is no earth... where is any fault current going to flow in order to create an Active / Neutral imbalance?
FollowUp 5 of 12
FollowupID: 511483   Submitted: Monday, Jul 02, 2007 at 16:46

Mike Harding posted:

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?
FollowUp 6 of 12
FollowupID: 511493   Submitted: Monday, Jul 02, 2007 at 17:29

RiCeYWA posted:

So Mike is it your opinion that the surge protector will not work if the gen isnt earthed?
FollowUp 7 of 12
FollowupID: 511498   Submitted: Monday, Jul 02, 2007 at 17:37

Mike Harding posted:

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
FollowUp 8 of 12
FollowupID: 511500   Submitted: Monday, Jul 02, 2007 at 17:45

RiCeYWA posted:

Well seeings Ive already purchased one is it worth having it on there anyways?
FollowUp 9 of 12
FollowupID: 511513   Submitted: Monday, Jul 02, 2007 at 18:57

Mike Harding posted:

It won't do any harm... but the answer to your question is... no :)
FollowUp 10 of 12
FollowupID: 511516   Submitted: Monday, Jul 02, 2007 at 19:08

RiCeYWA posted:

So how do they get away with selling a product that doesnt do what its marketed to do.
FollowUp 11 of 12
FollowupID: 511531   Submitted: Monday, Jul 02, 2007 at 19:32

Mike Harding posted:

We do not live in a perfect world my friend - sometimes... you have to look after yourself out there....
FollowUp 12 of 12
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AnswerID: 250317   Submitted: Monday, Jul 02, 2007 at 15:46

RiCeYWA replied:

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.
Reply 5 of 9
FollowupID: 511479   Submitted: Monday, Jul 02, 2007 at 16:24

Member -Dodger posted:

But will not stop the Genny blowing up.
Mike's answer is the correct one.
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FollowUp 1 of 6
FollowupID: 511480   Submitted: Monday, Jul 02, 2007 at 16:29

RiCeYWA posted:

Why would the genny blow up?

Im confused...
FollowUp 2 of 6
FollowupID: 511486   Submitted: Monday, Jul 02, 2007 at 16:57

Mike Harding posted:

_You're_ confused!? Join the club - _everyone_ on here is confused :)

This thread may help:
Site Link

FollowUp 3 of 6
FollowupID: 511491   Submitted: Monday, Jul 02, 2007 at 17:28

RiCeYWA posted:

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

FollowUp 4 of 6
FollowupID: 511509   Submitted: Monday, Jul 02, 2007 at 18:31

Robin Miller posted:

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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FollowUp 5 of 6
FollowupID: 511510   Submitted: Monday, Jul 02, 2007 at 18:33

Robin Miller posted:

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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FollowUp 6 of 6
AnswerID: 250333   Submitted: Monday, Jul 02, 2007 at 17:16

Gramps (NSW) replied:


Why not just earth it and be done with it ?
Regards


Al


Have you noticed that your memories, prior to colour TV, are in black and white
Reply 6 of 9
FollowupID: 511495   Submitted: Monday, Jul 02, 2007 at 17:30

RiCeYWA posted:

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
FollowUp 1 of 3
FollowupID: 511496   Submitted: Monday, Jul 02, 2007 at 17:31

Mike Harding posted:

Because that's not a _good thing_ to do with a small gen in a camping situation.
FollowUp 2 of 3
FollowupID: 511499   Submitted: Monday, Jul 02, 2007 at 17:43

Gramps (NSW) posted:


Bugga !!!! More bloody reading to do. Thanks :)))
Regards


Al


Have you noticed that your memories, prior to colour TV, are in black and white
FollowUp 3 of 3
AnswerID: 250342   Submitted: Monday, Jul 02, 2007 at 17:59

Glenn WA replied:

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
Reply 7 of 9
FollowupID: 511520   Submitted: Monday, Jul 02, 2007 at 19:16

Mark Taylor posted:

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
FollowUp 1 of 3
FollowupID: 511529   Submitted: Monday, Jul 02, 2007 at 19:31

Mike Harding posted:

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
FollowUp 2 of 3
FollowupID: 511600   Submitted: Monday, Jul 02, 2007 at 22:58

Member - Mike DID posted:

I think ELCBs also act as fast overcurrent trips.
Mike R
FollowUp 3 of 3
AnswerID: 250370   Submitted: Monday, Jul 02, 2007 at 19:46

Member - Norm C (QLD) replied:

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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Reply 8 of 9
FollowupID: 511538   Submitted: Monday, Jul 02, 2007 at 20:09

RiCeYWA posted:

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.
FollowUp 1 of 4
FollowupID: 511545   Submitted: Monday, Jul 02, 2007 at 20:24

Mike Harding posted:

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
FollowUp 2 of 4
FollowupID: 511558   Submitted: Monday, Jul 02, 2007 at 21:00

Member - Norm C (QLD) posted:

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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FollowUp 3 of 4
FollowupID: 511587   Submitted: Monday, Jul 02, 2007 at 21:56

Mike Harding posted:

>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
FollowUp 4 of 4
AnswerID: 250452   Submitted: Tuesday, Jul 03, 2007 at 10:09

Member - Mike DID replied:

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.
Mike R
Reply 9 of 9

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