Why is an exported earth bad?

[SPECIAL LOCATION]

i would class it bad practice and i think it may contravene to mechanical protection of the regs, will look in the red book after work

Agree with bad practice there Badger... but I think again this is one of those areas where the regs don't specifically say you cant...

electricians guide to building regs...

pg 685.7 garden light power shed & garages..

5.7.2 PVC cables should be protected from direct sunlight exposure.

permanently fixed in a protected location. (e.g. IMHO a shaded wall..)

Or mechanically protected

Or buried.

later its says UV will deteriorate PVC and should be replaced after 15 yrs..

IMO...

common sense says a short run to a light fitting can look really ugly with SWA or conduit over it, so PVC can be more aesthetically pleasing.

wheres as a long run to an outbuilding...

best put in SWA or PVC in conduit!

Also re the PVC T&E on an overhead... have seen this numerous times myself... but I wouldn't install that way...

normal T&E is NOT a flexible cable.. and not best suited to blowing around with movement in the wind! or animals climbing over it! :|

whereas SWA is not a solid core cable!

 

[SPECIAL LOCATION]

It's got it's own way in CU so on it's own MCB on the RCD side of the board

I would still add a double pole isolator switch as well..

cuz if you had a fault 'N' to 'E' on your external wire.. (chewed by rat / pierced by sharp object)

Your RCD will trip and you will need to isolate the 'N' and/or 'E' to get the RCD to reset,

which turning off the MCB will only isolate the 'L'.

could be a bit of a bum if it happens at an inconvenient time... :_|

 

[SPECIAL LOCATION]

Here you go Apache..

here's a big-un..

get your reading glasses out B-)and grab a couple of pints before you start!

Guiness DrinkGuiness Drink

A re-cap of earthing protection & methods employed to prevent shock..

from this hopefully you get a better understanding of the potential problems from exporting earth

 

[binky]

Also re the PVC T&E on an overhead... have seen this numerous times myself... but I wouldn't install that way...

normal T&E is NOT a flexible cable.. and not best suited to blowing around with movement in the wind! or animals climbing over it! :|

whereas SWA is not a solid core cable!

Did a job where garage was fed in T&E, with a return 2 way switch line for outside light in T&E, overhead from gable end, about 15m to garge in plastic pipe that was quite happily swinging in the breeze. The result was short from lighting to garage feed.

 

[Apache]

Specs a beer for you Guiness Drink

That's a great post and it makes so much sense.

Now if the earth was TT then I can see the installation has no potential difference with the general mass of earth.

BUT with the PME supplied by the electricity company (back to the sub-station?) could it not give rise to a potential difference between it and the mass of earth? IE the electricity company is exporting it's earth. Furthermore is this earth not shared with my neighbours?

My house has no gas and the water comes in in plastic.

 

[steptoe]

Specs a beer for you Guiness DrinkThat's a great post and it makes so much sense.

Now if the earth was TT then I can see the installation has no potential difference with the general mass of earth.

BUT with the PME supplied by the electricity company (back to the sub-station?) could it not give rise to a potential difference between it and the mass of earth? IE the electricity company is exporting it's earth. Furthermore is this earth not shared with my neighbours?

My house has no gas and the water comes in in plastic.

it is indeed my good friend, that is why your MEB and Earthing conductor must be large enough to not only carry a fault in your house, but also a fault in your neighbours as well.

the boy doth learnth fast,

I really must try dig out that link I had whereby a fault in an adjoining property caused a biggie for the neighbours!!!!

:O:O:O

 

[kme]

Sorry Apache, I`m a bit late on tonight - masses of paperwork (and it`s STILL not all finished:_|)

Never mind - time to unwind a little nowGuiness Drink

Just a point regarding T+E outside.

If your doors and windows are made from UPVC, and the cable is made from PVC; what`s the difference? Only the U

Which stands for??

UNPLASTICISED.

i.e. PVC cable is EXACTLY the same stuff your UPVC is made from, but with a plasticiser added, to allow flexibility.

NOW the fun bit............

When exposed to ultra-violet radiation (i.e. the sun), the effect on the PVC is to leech the plasticiser out of the cable.

Which means you end up with a cable which has the same make-up & constituents as a UPVC double glazed door. Which don`t tend to be very flexible.

On the contrary, UPVC is very brittle, and will crack easily.

As regards a specific reg; 522.11 seems VERY specific to me

 

[Apache]

As regards a specific reg; 522.11 seems VERY specific to me

What does it say?

 

[kme]

"522.11 Solar radiation (AN) and ultra violet radiation

522.11.1 Where significant solar radiation(AN2) or ultra violet radiation is experienced or expected, a wiring system suitable for the conditions shall be selected and erected; or adequate sheilding shall be provided. Special precautions may need to be taken for equipment subject to ionising radiation"

 

[Apache]

Thanks KME have one of your beers

 

[kme]

Why, thank you Kind sir;

Don`t mind if I do..............

Guiness DrinkGuiness DrinkGuiness DrinkGuiness DrinkGuiness DrinkGuiness DrinkGuiness DrinkGuiness Drink

Guiness DrinkGuiness DrinkGuiness DrinkGuiness DrinkGuiness DrinkGuiness DrinkGuiness DrinkGuiness Drink

....................... :^O Guiness DrinkGuiness DrinkPray.....................

....................... :^O Guiness DrinkGuiness DrinkPray.....................

..................Guiness DrinkGuiness DrinkGuiness DrinkGuiness Drink................

 

[Apache]

Should I disconnect my earth from the support wire?

 

[kme]

Should I disconnect my earth from the support wire?

Aye. I would, if it were mine.

 

[Apache]

Thanks mate. I'll do so tomorrow

 

[steptoe]

Should I disconnect my earth from the support wire?

while you're at it you should probably disconnect your shed/garage/workshop from the supply too.

not trying to be an ar5e here apache, but its really something I wouldnt even do as a temp measure.

all it takes is something simple and you could be lit up like a christmas tree.

 

[Apache]

I appreciate what you are staying steps, but some of the other chaps seem to think a wooden shed on wooden bearers with no extraneous conductors is likely to be fairly safe.

:|

 

[steptoe]

not a precise bearing on your situation apache, but just another aspect on the PME + rod scenario.

http://www.acoustica.org.uk/t/earth.html

fair enough apache, but whats the chances of you NEVER running a supply out of your shed to a lawnmower/radio/os light etc?

but if you're confident enough about your shed keeping you well insulated in the event of a fault then its fine, but bear in mind that even if your neighbour has a major fault then their current will be trying to find its way to earth down your bit of T&E as well.!

 

[Apache]

I'm hoping to get an extension in the new year. When I have a spark here I'll ask him about TTing me shed

 

[steptoe]

it prob be ok for a bit apache, I just personally HATE PME/TNCS if you hadnt already gathered,

I assume you have 30mA RCD on the house side of supply.

 

[Apache]

it prob be ok for a bit apache, I just personally HATE PME/TNCS if you hadnt already gathered, I assume you have 30mA RCD on the house side of supply.

Yes there's an RCD.

I can't see why each house can't just have it's own rod. It would surly be simpler...........