Protecting armoured cable

sparksburnout · Apr 10, 2015

Yeah I know it's an odd title. Currently looking at a job where an SWA runs down a garden to a shed, but it is just laying on the ground and looks rubbish. I am guessing the last installer left it like that due to the difficulty in burying it, so at least you can see it........ The only run is between stone/concrete and a line of old trees that have been cut down to ground level, there is no way I am going to be able to get down 600mm or anything like it as the roots are going to spread out, there are about 15 old stumps and It would be near impossible to dig them out. So, any ideas of the best way to protect the cable in a shallow trench? Is it possible to contain it in some kind of galvanised metalwork, or cap it with stone or similar, to prevent spades/forks and the like from penetrating it? I am only going to have a narrowish trench and I am guessing it is only going to go down maybe 150mm? Obviously the SWA on its own is not going to provide enough protection.

Darkwood · Apr 10, 2015

re-root it.... see what I did there!

davesparks · Apr 10, 2015

sparksburnout said:
Read the bloody OP. The last installer has left it on the surface and it looks ----. Its in an area where there is not going to be any disturbance of the ground as it will be covered over with a top dressing of broken slate. Personally I think it is unnecessary to try and get it down to 600mm as the disruption does not warrant the likely-hood of it being disturbed, I was originally thinking of going shallower and covering it with a protective barrier and tape - what's wrong with that?

Calm down, I was only asking what the customer had asked you to do! It seems odd to employ an electrician to dig a hole, and very expensive!

There's nothing wrong with it if you are happy that you can satisfy the regulations. Personally I have had ducts covered with concrete if I have not been happy with the depth the trench could be dug to.

Deleted member 26818 · Apr 10, 2015

Why does the cable need protecting?
It's armoured.
What's with the 600mm, is this on a farm or something?

davesparks · Apr 10, 2015

spinlondon said:
Why does the cable need protecting?
It's armoured.
What's with the 600mm, is this on a farm or something?

It is a common misconception that the term 'armoured' when applied to a cable means that it is somehow impervious to mechanical damage, it is not. A slight scratch of the outer sheath is enough to ruin the cable.

sparksburnout · Apr 10, 2015

davesparks said:
Calm down, I was only asking what the customer had asked you to do! It seems odd to employ an electrician to dig a hole, and very expensive!

There's nothing wrong with it if you are happy that you can satisfy the regulations. Personally I have had ducts covered with concrete if I have not been happy with the depth the trench could be dug to.

Calm.............3rd pint of proper job. Concrete cap seems like a good idea to me, along with marker tape. The ground in question is very unlikely to be disturbed by "normal" activities.

Deleted member 26818 · Apr 10, 2015

Do me a favour.
All that would happen, is that the steel wire would start to corrode.

Marvo · Apr 10, 2015

We had some SWA cables that were running up a mountainside that was fairly heavily forested. The cables were mostly surface at the request of the customer to save the cost of digging trenches in heavily rooted ground. They lasted a few months until the porcupines tore them to shreds. Eventually they agreed to have them buried and we dug a very small and shallow trench using hand axes and spades which was approximately 150mm wide and maybe 200mm deep. We laid the cables in the trench and placed pre-fabricated concrete vibracrete fence posts over the top of them which has a notched profile that fitted the cables nicely.

[ElectriciansForums.net] Protecting armoured cable

davesparks · Apr 10, 2015

spinlondon said:
Do me a favour.
All that would happen, is that the steel wire would start to corrode.

Yes, the protective conductor corrodes, can you not see the problem with that?
Armour which has rotted through will not be able to stand a fault current very well, whether it is being used as the cpc or just as earthed armouring.

sparksburnout · Apr 10, 2015

davesparks said:
Yes, the protective conductor corrodes, can you not see the problem with that?
Armour which has rotted through will not be able to stand a fault current very well, whether it is being used as the cpc or just as earthed armouring.

Good points. You can't leave it on the surface or not deep enough, if it gets damaged then the XPLE will leak and the armour will rot away leaving it vulnerable. You could easily nick it with a spade or whatever and not realise, but then over time the armour would become useless, might as well just be T&E buried. Even at 600mm that could happen. I reckon I am going to go as deep as possible and bed it in sand and then a concrete cap and tape?

Leesparkykent · Apr 10, 2015

sparksburnout said:
Good points. You can't leave it on the surface or not deep enough, if it gets damaged then the XPLE will leak and the armour will rot away leaving it vulnerable. You could easily nick it with a spade or whatever and not realise, but then over time the armour would become useless, might as well just be T&E buried. Even at 600mm that could happen. I reckon I am going to go as deep as possible and bed it in sand and then a concrete cap and tape?

sounds good

davesparks · Apr 10, 2015

sparksburnout said:
if it gets damaged then the XPLE will leak and the armour will rot away leaving it vulnerable.

You'd hope the protective device will operate if something has got that far through the cable!

Delboybully · Apr 10, 2015

Either leave it on the surface or get a groundsman to dig it properly. Simples

trev · Apr 10, 2015

Unless there's a load of slack on this you are not going to get it very deep mate. A concrete cap might be your only option

sparksburnout · Apr 10, 2015

Delboybully said:
Either leave it on the surface or get a groundsman to dig it properly. Simples

A groundsman?? It's some buggers back garden not Wembly ***ing stadium.

Leesparkykent · Apr 10, 2015

sparksburnout said:
A groundsman?? It's some buggers back garden not Wembly ***ing stadium.

Probably meant a groundworker.

Protecting armoured cable

sparksburnout

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Darkwood

davesparks

Deleted member 26818

davesparks

sparksburnout

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Deleted member 26818

Marvo

-

davesparks

sparksburnout

-

Leesparkykent

davesparks

Delboybully

-

trev

sparksburnout

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Leesparkykent

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