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B

Bobster

So here's the situation I have 3 mobile lighting towers to rig up in the bottom of a quarry. Now I was just going to drive in an earth rod for each one as it just not feasible to earth them in any other way. However the more I think about it I'm not sure how good an earth the rod will provide as they will be driven into a limestone bed.

How would others go about solving this problem, has anyone done something similar.
 
if the are fed by a genny, then i would install a rod per genny just to tie the potential to ground. At least there will be no potential difference then. I suppose you coule leave the sytstem as a floationg earth if you wish, as nobody should really have to touch the gear unless turning it off or on.Im guessing it will be barriered off from machinery ect anyway.
 
if the are fed by a genny, then i would install a rod per genny just to tie the potential to ground. At least there will be no potential difference then. I suppose you coule leave the sytstem as a floationg earth if you wish, as nobody should really have to touch the gear unless turning it off or on.Im guessing it will be barriered off from machinery ect anyway.

Yes they have a diesel generator built in. Just haven't found anything in the regs aside from 551.4.3.2.1 which says a suitable means of earthing shall be provided. Now I'm not sure if that's applicable to my situation as that's for generating systems that provide a alternative distribution of electricity to the public.
 
If your not sure an earth rod will do the job, think about installing an earth mat.
Also, bond between the genny and tower, ensure the Gennys neutral is linked to earth as well.
 
In myn experience with lighting towers, they are all bonded correctly by the manufacturer.

have a read of 2.4 in the green OSG.


it basiclly states that all the earth rod will be doing, is referencingthe genny to earth. The system will still be a TNS.
if other extraneous metalwork or exposed conductive parts from another installation are present then you should bond them together to prevent touch potentials.

If a floating earth is used, ie the neutral of the genny is not tied to earth, and no rod is supplied, then all circuits must have RCD protection, and there is no risk of contact between the genny and anything fed from it, and any other extraneous metalwork, or exposed conductive parts from another installation
 
A quarry? They have some fun toys.

Get the owners to dill a 50mm shot hole by each lighting position about 10m deep. They won’t take long to drill. Put the rods in and fill with bentonite or urea. Urea is cheaper but pongs when you add water to it. It also acts faster than bentonite.
The generator, one spike at two diagonal corners. Make sure the neutral is properly earthed.
 
A quarry? They have some fun toys.

Get the owners to dill a 50mm shot hole by each lighting position about 10m deep. They won’t take long to drill. Put the rods in and fill with bentonite or urea. Urea is cheaper but pongs when you add water to it. It also acts faster than bentonite.
The generator, one spike at two diagonal corners. Make sure the neutral is properly earthed.
There I told you Tony was your man!
 
A quarry? They have some fun toys.

Get the owners to dill a 50mm shot hole by each lighting position about 10m deep. They won’t take long to drill. Put the rods in and fill with bentonite or urea. Urea is cheaper but pongs when you add water to it. It also acts faster than bentonite.
The generator, one spike at two diagonal corners. Make sure the neutral is properly earthed.


The 3.3kv Navi's are pretty good to work on albeit it's a little bit archaic. I'll ask tomorrow about getting them to move the drilling rig round. In all probability they will just scrap using the lighting towers and just let the drivers use headlights.
 
A quarry? They have some fun toys.

Get the owners to dill a 50mm shot hole by each lighting position about 10m deep. They won’t take long to drill. Put the rods in and fill with bentonite or urea. Urea is cheaper but pongs when you add water to it. It also acts faster than bentonite.
The generator, one spike at two diagonal corners. Make sure the neutral is properly earthed.

Even one deep rod as described above could possibly suffice if this is a for a very temporary installation...

The 3.3kv Navi's are pretty good to work on albeit it's a little bit archaic. I'll ask tomorrow about getting them to move the drilling rig round. In all probability they will just scrap using the lighting towers and just let the drivers use headlights.

If your talking about a quarry situation, then your, or the workers employers have a duty to ensure safety on the site. As Tony has stated M&Q rules apply which are by far, stronger in the legal arena than BS7671. In fact as i recall, quarries have their own set of rules and regulations...
 
As an M&Q electrician you are under obligation to the Secretary of State.
It is called you’re Statutory Instrument of Competence.

Imprisonment is the ultimate punishment!
 
Even one deep rod as described above could possibly suffice if this is a for a very temporary installation...

Probably there for a week tops.

If your talking about a quarry situation, then your, or the workers employers have a duty to ensure safety on the site. As Tony has stated M&Q rules apply which are by far, stronger in the legal arena than BS7671. In fact as i recall, quarries have their own set of rules and regulations...

This is why I was asking advice, because of the ground material I wouldn't have thaught a normal earth rod would provided a good enough earth.
 
A quarry? They have some fun toys.

Get the owners to dill a 50mm shot hole by each lighting position about 10m deep. They won’t take long to drill. Put the rods in and fill with bentonite or urea. Urea is cheaper but pongs when you add water to it. It also acts faster than bentonite.
The generator, one spike at two diagonal corners. Make sure the neutral is properly earthed.

Would the supply from the Genny to the lights be RCD protected?
What sort of circuit breaker would be used in the event of an earth fault?
Just curious.
Thanks.
 
Rcd then through (off the top of my head) a 32A breaker. Feeding 4 x 1000w lamps.
 
Rcd then through (off the top of my head) a 32A breaker. Feeding 4 x 1000w lamps.

Why wouldn't you get the quarry company to drill a shot bore for your earth rod(s) as Tony suggested, they must be drilling the things every day anyway!! Not as if the rods, couplers, etc, are going to be wasted, as you just pull the things out of the Bentonite soil enhancer when your done with the temporary lighting installation...

You could well be surprised by the value you obtain, going down 10 metres as Tony suggested. Limestone can be full of fissure's that hold ground water and dissolved conductive sulphates and chlorides etc .. lol!!
 

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