Metal plate to protect earth bonding cable

[JohnW2]

do the requirements for cables to be in safe zones (or otherwise protected) actually extend to bonding cables?

The regulations don't say they don't.

I agree that the regs don't explicitly say that it doesn't apply to bonding conductors, but the spirit of the regs maybe implies that.

In particular, 522.6.101(i) allows a cable to be buried <50mm deep if it has an 'earthed metallic covering'. If the entire (and only) conductor is already earthed (at least as well as any covering would be), such a covering would obviously achieve nothing - and suggest to me that the regs don't really intend the 'buried cable rules' to apply to cables which contain only bonding/earthing conductors.

Kind Regards, John

 

[EFLImpudence]

What about the regulations which state that some protective conductors - supplementary and earthing - shall be larger if not mechanically protected?

I realise that running a 16mm² instead of 10mm² bonding conductor would not make the situation significantly different but a hidden conductor, whilst not a danger to anyone drilling, would present a danger should that conductor be unknowingly severed.

 

[JohnW2]

What about the regulations which state that some protective conductors - supplementary and earthing - shall be larger if not mechanically protected?

As you say, that applies specifically to supplementary bonding conductors and earthing conductors - and we use the specified larger cables if there is no mechanical protection. However, how often do you see a main bonding conductor which is 'mechanically protected', and where is the regulation which says that a MPB/MEB conductor has to be larger if it isn't 'mechanically protected'?

I realise that running a 16mm² instead of 10mm² bonding conductor would not make the situation significantly different but a hidden conductor, whilst not a danger to anyone drilling, would present a danger should that conductor be unknowingly severed.

True - but, as I said, the regs would be quite happy if the bonding conductor (buried <50mm) had an 'earthed metallic covering' (not necessarily providing significant mechanical protection) - which tends to make nonsense of the whole thing.

Kind Regards, John

 

[f0rmula]

Could you put the CU and water entry positions on the model, and post the .skp on a file sharing site?

Hi. Yeah, I didn't realise anyone would use sketchup in here.

I've put a semi-tube on the wall where the water supply comes in, and a 400*500*200mm box on the wall in the cellar where the consumer unit is.

http://speedy.sh/f9Nbk/MortonStreetPlusEarthStuff.skp

(sorry for annoying download site. click the link right at the top)

 

[ban-all-sheds]

Cheaper/better to get some lengths of steel conduit and joints and sink it in teh wall.

It might be enough to just remove the plaster, and rout a small channel in the skirting board - no actual chasing of masonry required.

Interesting question for all - could you just use the conduit as the bonding conductor? (Assuming the csa is OK - I've not checked)

 

[Lectrician]

do the requirements for cables to be in safe zones (or otherwise protected) actually extend to bonding cables?

The regulations don't say they don't.

I agree that the regs don't explicitly say that it doesn't apply to bonding conductors, but the spirit of the regs maybe implies that.

In particular, 522.6.101(i) allows a cable to be buried <50mm deep if it has an 'earthed metallic covering'. If the entire (and only) conductor is already earthed (at least as well as any covering would be), such a covering would obviously achieve nothing - and suggest to me that the regs don't really intend the 'buried cable rules' to apply to cables which contain only bonding/earthing conductors.

Kind Regards, John

If you damage a bonding cable by drilling or driving a screw or nail through it, you would not likely be aware you have caused the damage. I would say it should therefore have some mechanical protection to prevent this, although the regs (as you say) are vague in this matter.

 

[EFLImpudence]

True - but, as I said, the regs would be quite happy if the bonding conductor (buried <50mm) had an 'earthed metallic covering' (not necessarily providing significant mechanical protection) - which tends to make nonsense of the whole thing.

But where bonding and earthing conductors mechanical protection is required no mention is made of the method (conduit or otherwise) and no mention is made of earthing it - which is obviously pointless and useless.


As for using the conduit as the bonding, this is allowed where applicable, isn't it?.
However, I suspect some will retort that the bonding conductor should be continuous but this is obviously not so because conduit, armour etc. can be used as bonding.

 

[ban-all-sheds]

I've put a semi-tube on the wall where the water supply comes in, and a 400*500*200mm box on the wall in the cellar where the consumer unit is.

http://speedy.sh/f9Nbk/MortonStreetPlusEarthStuff.skp[/QUOTE]
Err.... ?

 

[JohnW2]

Interesting question for all - could you just use the conduit as the bonding conductor? (Assuming the csa is OK - I've not checked)

I would imagine so. 543.2.1 (which is not subject to the copper-only restriction of 543.2.4) and 543.27, amongst others, allow a protective conductor in general to be the conduit, and 5441.1.1, together with Table 54.8 give the required CSA of main protective bonding conductors in terms of 'copper equivalent', without any mention of any type, or material, of conductor not being acceptable. Of course, if the conduit did not go all the way from the MET to the extraneous-c-p being bonded, there would be 'joins' in the MPB conductor, which some people don't seem to like (even though I can find no regulation against it).

I have to say that I'm still not convinced, at least in terms of the regs, that any such protection for a bonding conductor is required at all.

Kind Regards, John

 

[JohnW2]

If you damage a bonding cable by drilling or driving a screw or nail through it, you would not likely be aware you have caused the damage. I would say it should therefore have some mechanical protection to prevent this, although the regs (as you say) are vague in this matter.

That's sensible. However, the regs are not just vague, they actually offer specific permitted options that would not necessarily offer any appreciable mechanical protection (e.g. an 'earthed metalic covering', which could be tape etc.). The regs clearly are thinking about the protection of live conductors.

Kind Regards, John

 

[JohnW2]

But where bonding and earthing conductors mechanical protection is required no mention is made of the method (conduit or otherwise) and no mention is made of earthing it - which is obviously pointless and useless.

I think, but am not sure, that you are agreeing with me.

Kind Regards, John

 

[f0rmula]

I've put a semi-tube on the wall where the water supply comes in, and a 400*500*200mm box on the wall in the cellar where the consumer unit is.

http://speedy.sh/f9Nbk/MortonStreetPlusEarthStuff.skp[/QUOTE]
Err.... ?

You need to turn on and off the right layers

Window -> Layers, then turn on and off stuff. The kitchen is on the 'Downstairs' layer. The sketchup was saved with the camera looking at the consumer unit in the cellar.

 

[EFLImpudence]

I think, but am not sure, that you are agreeing with me.

Yes, agreeing and confirming.


Back to the bonding route -

Is there removable floor covering?
Could a very small channel be made in the concrete?

 

[ban-all-sheds]

You need to turn on and off the right layers

Ah - I guess this is me and Sketchup:

 

[JohnW2]

Here's the run in question. I was planning to have the earth bonding enter from the cellar, through the side of the door architrave, then run along the bottom of the wall, but that's not going to happen now

I suspect that you would not regard it as aesethetically acceptable, but you could just clip the cable ('exposed') to the top of the skirting, and then paint it - not totally beautiful, but no worse than the BT man would do with a telephone cable!

Kind Regards, John