In the Video, Doncaster Cables advises against the use SY as power cables. Do we Stick to manufacturer’s recommendations?

Doncaster Cables advises against the use SY as power cables. Do we Stick to manufacturer’s recommendations?

That video also seemed to say that no-one makes SY in the UK any more ... but Doncaster (according to their web site) only have one manufacturing facility (in Doncaster) - so is their SY UK made or not?

Even their Web page for SY says it's rated for 300/500V, generally meets  BS EN 50525-2-11 (i.e. the standard for mains flexes) and even goes as far as saying  "This cable is also used by electricians in certain fixed installations where only light mechanical stress may occur. " which doesn't feel like an official condemnation.

So still as clear as mud. What's needed is for a proper standard to cover SY (and CY) cables.

   - Andy.

I'm inclined to agree - to set the UK ghosts to rest, although the rest of the continent does not seem so worried,  there probably needs to be a BSI type standard defining the minimum CSA of the copper, the voltage withstand of the insulation core to core and the core to braid, and then the maximum braid resistance per unit length and perhaps for us EMC obsessed types, the braid optical coverage fraction.
In reality I've yet to be delivered any that was unsafe to use or failed on insulation tests.

For a bit of  laugh, as we have the facility, we have from time to time subjected cable samples to gross over-voltages to see the true breakdown behaviour, and it is always many times the test limits - think  high 10s of kV - it is the air spacing at the exposed ends that is the point of breakover in all normal mains connectors.

And yes, that video short is slightly at odds with the written word on their website.

Mike

Voltage rating of wires is an interesting topic. It is typically determined by testing samples over a range of voltages and recording the time to failure. The results are then plotted to determine the long term withstand voltage. A factor of safety, to allow for manufacturing defects and tolerances, is then applied. A piece of typical PVC equipment wire will have a short term withstand of 20kV or more, a long term withstand of around 6kV and a rating of maybe 600V. It’s not a precise science. The minimum insulation thickness is more often determined on mechanical rather than electrical grounds.

This reminds me of that thread I created

BS7671 says refer to MI

engx.theiet.org/.../142399

This is an old chestnut that surfaces reasonably often.  I had an engaging and enlightening discussion on this thread https://engx.theiet.org/f/wiring-and-regulations/24346/multicore-cables-yy-but-not-pvc-pvc.

The problem of lack of a construction standard has not yet been resolved as far as i know.

Mike, you should only use SY,YY,CY cable for control, not power circuits as the insulation is substandard and not to any standard at all

Andy,

You should not use this cable for Air con installations where it goes external, it has no UV protection and the installation will degrade, also BS7671 discourages the use due to it not being made in the UK or Europe under any manufacturing standards, so you can't rely on the manufactures data, also there are no tables for Volt drop etc to calculate from

Parts of that argument are a bit specious. The copper cores are of course made to a standard, just not one invented here, and knowledge of the stranding and copper purity from that allows those skilled in the art to deduce a resistance and a voltage drop- tables in OSG or '7671 are for those who can't, but those who can, are allowed to.

Makers of doubtful integrity can of course claim to meet a BS and fail to do so, just as much as they can claim and fail to meet a DIN.

The problems arise, as you point out, from its poor performance in UV, which is a matter of sensible routing and containment,  (much as it would be for "Arctic flex" or twin and earth) and specifically folk not knowing how to terminate the braid, or not realizing it is woefully inadequate for use as the CPC without a parallel inner core, and being pretty wispy is not really much of a protection against nails..
The fact it is tested at  650V and not 1000V in the factory is actually something of a reg herring, as in practice the insulation breakdown is many kV.

It would  be possible to write a BS for it, but as others have noted, it suffers from the not invented here problem, and the makers are not that bothered about doing extra tests just for the UK market.

Mike.

Have eFIXX been reading this forum? https://www.youtube.com/watch?v=FCYSdor7-CI