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Earthing portable generators properly...
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Richie T View Drop Down
Young Croc
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    Posted: 24 May 2012 at 6:00pm
Soundsystems - Freeparties... if using portable generators for sound equipment please MAKE SURE that you do the following:

1) The neutral and earth are commoned (joined) inside the generator, or by means of a special adapter plugged in designed for such purpose and
2) the generator chassis is properly earthed via means of an earth rod.

Its in section 2.4 clearly detailed in the on-site guide of the wiring regs BS7671:2008 (2011) - see figures 2.4.3 (i and ii)

Failure to do this might mean any connected RCD's may not trip when theres a fault, or with damp conditions and... someone could die. Its to do with using more than one Class 1 appliance connected.

If youre in doubt on how to do this then I can supply custom 16 amp leads which will ensure the above requirements are met. These are:

16 amp (blue) m-f specialist neutral/earth link cable 0.3m - £20.00
As above with inline RCD - £40.00

For another £10 I can supply an earthing kit which would attach to the generator chassis.

Note - larger generators (generally above 10kVA) will already comply. If in doubt give me or any qualified sparky a shout and whatever you do DONT just join the neutral/earth on any old lead as that can be dangerous.

Now be safe and party hard!
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Blaize110 View Drop Down
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Points: 673 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Blaize110 Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2012 at 6:11pm
I am not 100% sure on this, but I think there was something in a topic a while ago about not needing an earth-spike for a system below a certain power, and how the recommendation is actually to leave the earth floating and just rely on the RCD.



EDIT:

12. The possible gains from deliberately earthing a small single-phase system, for correct operation of what is at best supplementary protection, are unlikely to 

outweigh the safety and economic advantages of using the system as a simple floating system in the first place.

30. Floating systems, particularly when limited in extent and under close supervision, do not introduce possible consequential hazards which may arise from 

deliberately earthing an initially separated single-phase generator winding. 




Edited by Blaize110 - 24 May 2012 at 6:21pm
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Mrd999 View Drop Down
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Points: 515 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Mrd999 Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2012 at 6:25pm
Was wondering about this earlier, have never earthed generators in the past, just thought that the actual cage touching the ground was good enough.Obviously not.
All info appreciated as  will be the guy sorting all this out at our parties this time around.
What goes around, comes around
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Richie T View Drop Down
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Points: 611 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Richie T Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2012 at 6:46pm
Never rely solely on an RCD it goes against the EAWR 1989 -

Section 8 "Regulation 8 Earthing or other suitable precautions
Precautions shall be taken, either by earthing or by other suitable means, to prevent danger arising when any conductor (other than a circuit conductor) which may reasonably foreseeably become charged as a result of either the use of a system, or a fault in a system, becomes so charged; and, for the purposes of ensuring compliance with this regulation, a conductor shall be regarded as earthed when it is connected to the general mass of earth by conductors of sufficient strength and current-carrying capability to discharge electrical energy to earth"

- and GN 138 of EAWR 1989

"138 Many accidents have been caused by the metalwork of portable or transportable equipment becoming live as a result of the combined effects of a fault and high impedance protective conductor connections. The danger may be reduced by the use of a residual current device (RCD) designed to operate rapidly at small leakage currents (typically not exceeding 30 mA), although these devices do not eliminate the risk of electric shock. RCDs should be considered only as providing a second line of defence. They should be operated regularly using the test trip button. This test trip procedure is important in maintaining the effectiveness of most types of RCD."

I think whoever wrote the HSE info needs look again at the information they are given.

Heres the info from the IET wiring matters magazine with diagrams... http://electrical.theiet.org/wiring-matters/39/portable-generators.cfm?type=pdf





Edited by Richie T - 24 May 2012 at 6:46pm
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djeddie View Drop Down
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Points: 4125 		Post Options Post Options   Thanks (0) Thanks(0)   Quote djeddie Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2012 at 6:48pm
Is this thread to give advice or to try and sell your products?
Chas n Dave : it's like Drum and Bass but with beards.             E=mc² ±3dB
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Richie T View Drop Down
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Points: 611 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Richie T Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2012 at 6:49pm
Its for advice as I said you can consult me or any other qualified electrician :) 
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jacethebase View Drop Down
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Points: 5699 		Post Options Post Options   Thanks (0) Thanks(0)   Quote jacethebase Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2012 at 6:51pm
So when a bit of metal equipment fails and becomes live you have to wait for someone to touch it before the RCD trips? 
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Richie T View Drop Down
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Points: 611 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Richie T Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2012 at 6:56pm
If its floating that can happen - just one of many scenarios. ALso on a floating system with class 1 appliances, you only need a live to earth fault (say in amp) and a neutral-earth fault on mixer (both class 1) to put 240v across both chassis... person touching mixer decides to adjust amp and rcd wont trip because the person still balances the circuit even though they are blown sky high. Thats putting it in laymans terms :)
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jacethebase View Drop Down
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Points: 5699 		Post Options Post Options   Thanks (0) Thanks(0)   Quote jacethebase Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2012 at 7:01pm
I have never known anyone not put a earth rod out on purpose. Seems a bit daft really.
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Blaize110 View Drop Down
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Points: 673 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Blaize110 Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2012 at 7:07pm
Originally posted by jacethebase jacethebase wrote:

So when a bit of metal equipment fails and becomes live you have to wait for someone to touch it before the RCD trips? 

Originally posted by Richie T Richie T wrote:

you only need a live to earth fault (say in amp) and a neutral-earth fault on mixer (both class 1) to put 240v across both chassis...
 
 

If the case is earthed when the live shorts to it, then surely the current will flow back down the earth, due to the earth and neutral being bonded in the genset (before the RCD). This path back to the generator effectively 'bypasses' the RCD and means the RCD should detect the 'missing' current and so trip.


Edited by Blaize110 - 24 May 2012 at 7:10pm
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Richie T View Drop Down
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Points: 611 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Richie T Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2012 at 7:17pm
not if theres no earth reference to the alternator coil.... as all youre doing is putting a fault across L&N - the earth 'star point' being nearest to the fault with least resistance. 
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chris392 View Drop Down
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Points: 150 		Post Options Post Options   Thanks (0) Thanks(0)   Quote chris392 Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2012 at 8:10pm
A guide to earthing gennys would be usefull. I take it creating a new earth also needs to be done with long extension leads?
Is it as simple as bashing a steel rod in the ground? Like those 1m long steel pegs used for tape fences and such. And then connecting to the gennys frame?
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