It's not just a case of whether the ducting offers as much physical protection as the armour.
The armour will earth any metallic tool which penetrates or cuts the cable, ultimately tripping the supply.
This is true of 2 core concentric cable with the earth+neutral on the outer conductor, even if the outer is ali or copper.
Earthed armour (etc.) is only required if there is no adequate duct to provide mechanical protection:
Reg. 522.8.10 "Except where installed in a conduit or duct which provides equivalent protection against mechanical damage, a cable buried in the ground shall incorporate an earthed armour or metal sheath or both, suitable for use as a protective conductor. The location of buried cables shall be marked by cable covers or a suitable marking tape. Buried conduits and ducts shall be suitably identified. Buried cables, conduits and ducts shall be at a sufficient depth to avoid being damaged by any reasonably foreseeable disturbance of the ground.
"Note: IEC 61386-24 is the standard for underground conduits."
Amen.
I think there is some conflating of issues here. The need for ducting to provide mechanical protection is only in cases where the cable does not have an earthed metal enclosure (which may or may not be "armour" as such).
If you are talking about a SWA for example, then that is suitable for direct burial without any additional protection (save ensuring the trench has no sharp objects, and a warning tape is laid above it). Hence ducting round a SWA does not need to provide mechanical protection at all, and in many cases will simply be there to make the pulling of the cable (or addition of further cables etc) easier later.
So the non complying (but common) case of conventional flex in a hose pipe is non complying because the flex is not of a design with a concentric earthed layer on the outside, and the hose does not offer mechanical protection to it. Satisfying *either* of those requirements could make it acceptable.
No, well the purpose of the protection is to ensure the supply is disconnected when you damage the cable, not to make it invulnerable to damage (which with even a small digger will take some doing!)
ill start with "dig it up". Please don't fail me ;-)
a water feature. It is rubbery mains cable, and I need to get it through th= e ducting. The ducting is 19mm internally, and has a slightly "grippy" feel= ing to its inside, as does the cable.
it gets stuck at the tiniest of curves. I have tried sucking it down with = a vacuum, which has been no more successful.
ith a vacuum cleaner without any problems. So, I'm guessing the issue is fr= iction - rubbery plastic against rubbery plastic.
t around the curves? I could dig the trunking up, but if the water feature = (a small, sealed pump) ever failed, then I would need to get a new cable do= wn.
and it made matters worse, I may be stuck with trunking I can't use at all.= The pump cable needs to thread through the base of the water feature first= , so the cable could not have been put in before the trunking was installed= .
Okay, I'm sorted now :-)
I ordered some of the recommended lubricant. It seems to be some kind of wa= ter-based emulsion, quite thick, and works really well. I used a nylon cord= to pull the cable through, and got it done in no time. The nylon cord suck= ed down with a vacuum cleaner hooked onto one end. Being water-based, the l= ubricant cleans up dead easy with a simple wipe.
One of the tricks seems to be to keep the cable moving. As soon as it stops= moving, it is more difficult to get it started again. If you keep it movin= g, and feed in a little of the lubricant a the same time, it just keeps goi= ng with virtually no resistance.
So now we have a trickle of water in the garden, doing its trickly thing. N= ow back to the summer-house construction. Oh, she's a hard task-master...
-- Jason
Excellent. Did you actually try talcum powder first? That was the traditional way when I was doing conduit stuff - many years ago. Be interesting to have a comparison - since talcum is cheap and easily got.
I didn't try talc, no. Nor washing up liquid. I kind of jumped at the lubri= cant, since it was easy to get hold of, and cheap (no P&P and arrived withi= n 36 hours). I've got most of a litre of that left over now, so looking for= some excuses to use it. I would probably be looking for excuses to use the= left-over talc too, if I had gone down that route. Not sure which would ha= ve been the most fun.
Hopefully this thread will be useful to others.
-- Jason
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