SY Cable containment

It rather depends how  it is being used. If you consider that the giblets of it are rather like arctic flex, but with an over braid and outer plastic jacket, you may argue that at least anywhere that a fatter, slightly less flexible but tougher arctic flex would be OK, so is SY, and arguably a few other places where the flex alone would be a bit too weak.
The uncertainty is how much you might rely on the braid either as a CPC or as an earthed 'armour' to allow routing out of a 'safe' zone.  Now the braid resistance of all but the shortest length is not really low enough for a CPC on its own, (the braid resistance is not a well controlled parameter) and rather like cables protected by thin foils, there is a risk that if the cable was stabbed by  a nail or similar, that the braid wires might just burn back from the point nearest the damage without actually blowing a fuse. So if you want to route it 'out of zone' into places where nail and screw damage is likely, especially without RCD protection, then perhaps it is not enough.

That said we use lots of it in test chamber lab set-ups and for RF shielding, and it is very reliable in practice. Terminating the braid well needs more than passing thought, as it does not work with SWA glands, but there are special glands, or the braid can be combed into a tail and then crimped or terminated like the other cores.

If there was a proper standard performance for the braid density/resistance it would probably raise fewer concerns.

Also some makes declare it as 300/500V rather than 0.6/1kV , but that is a false worry, as the insulation is still tested to several kV and on normal 230/400 3 phase it is perfectly fine, as above, downstream of appropriate protection, be that MCB and/or RCD.

Mike,

Hi Mike

Thanks for the response. 

To give a bit more background, I was performing some survey work at a site and noticed that additional sockets had been spurred off using surface mount SY cable. To that end, it would be RCD protected so I think it's safe in terms of the wiring regs. 

My query would be where and  how are the cables routed, and are they using a copper core as the main CPC or just the braid ? Assuming surface mount is not  in a silly place and going to be damaged, and there is a good R2 result, then fine.

But yes, a slight roll of the eyes maybe, but does not sound like it is worth troubling the scorers on this one.

Mike

My main concern regarding the use of this cable type is the rather high and variable resistance of the braiding. This matters little as regards effective earthing of the connected load since one of the copper cores can be and in most circumstances should be used as the CPC.

That however does not tell the whole story. Consider the consequences of a fault between phase and the earthed braid, perhaps as a result of impact damage, part way along a long run of SY. The resistance of the braid might limit limit the fault  current to a value too low to promptly operate the fuse. A high resistance arcing fault could persist for long enough to start a fire.

An RCD should save the day, but not all circuits require one. AFDD likewise.

Around five years ago I wired some prefabricated steel garage inspection pits, including some for VOSA.

These are huge, big enough to park artic lorries and trailers over them with some being sectional, they were made in the fabricators workshop then transported to site on artics and set in concrete in holes excavated in the garage workshop floor, one was an above ground pit and galvanised for a firm that pressure wash’s and steam cleans lorries with ramps to get them up on to it.

I did question the wiring spec, but was told it was what the customers wanted, SY cable run in steel tubes welded to the inner face of the steel walls, but without elbows and other fittings so the SY went is unprotected for a few inches.

I did however use the correct SY cable glands to earth and seal the cables at accessories, which I have never seen anyone else do, despite having seen SY used in some “prestige” premises, but basically as an extension lead thrown on the ground to supply outdoor equipment such as a water aerator on a lake at premises of historical and cultural importance cared for by a national organisation I pay a monthly subscription to, so I can visit such places. Plastic stuffing glands seem to be the fittings generally  used or some tape wrapped around the end.

www.cef.co.uk/.../23106-20-m20-cxt-industrial-cable-gland-sold-in-1-s

My two local independent electrical wholesalers loved me, I bought all their stocks of SY cable glands at a knock down price and cleared the stock for them, though now I still have some in my garage along with the tail end of a roll of cable to use somewhere.

That was a job that turned sour for me, The fabricator went bust having emptied the workshop elsewhere and starting again under a new name thirty miles away leaving them owing me £1,500 on my last invoice, which was a lot less than most of the others owed money.

SY termination.....

SY Cable or SY Flex How to Terminate, Make Off Step by Step Practical Demonstration of Connecting - Bing video

Right time consuming and fiddly terminating.

Z.

 Zoomup 

After making off a couple of hundred you will certainly make them off in less than nineteen minutes, it helps to have the right tools, for this job a pair of electricians scissors are ideal for terminating SY cables.

http://www.ck-tools.com/products/ck_tools/electricians_tools/cable_cutting/electricians_scissors/

When we did SWA terminating at college the Head of Department our usual lecturer handed us over to the workshop technician for the evening, because he used to work for a traffic light installation company and had made off more small SWA cables that most electricians ever will, making off SY is a variation of the technique he taught us.

In many ways the 'universal'  dual pig tail grooved glands are easier than the fully circumferential compression type. Can actually be quite a bit faster than doing SWA in practiced hands.  And you can still use a pirahna nut inside the box if you wish.

But yes a lot of folk do seem to cock it up. Note in this 3 min video he should have threaded the body onto the cable before teasing the braid !  It is a rookie error, like wiring a BS4343 plug without the backshell.
There are very few realistic  cases where you can thread the gland body on to the cable from the other end afterwards, but luckily for him a demonstration on a 3 ft length in a classroom is one of them.

Mike

I really cannot understand why SY or YY cables are not acceptable to BS7671. We used to use miles of the stuff in heavy industry. It's odd that the Bodies are only too quick to 'harmonise' with foreign standards, even the dreaded and suspect AFDDs from the USA, yet SY & YY seem to be orphans who have been left out in the cold.

Arctic cable is quite often left out in the cold ;)