I'll start then. With the braid earthed, it's certainly more robust/safer than say T&E or plain sheathed flex in the same situation - especially with an RCD (or even a low rated MCB) upstream and PFC not too high. Having some sort of screen is probably better than nothing EMI wise too. Leaving the screen unearthed seems to be asking for the worst of both worlds - they might as well have used simple (and cheaper) flex.

For fixed wiring I'd say SY/CY falls into a similar camp to BS 8436 (nail shield) cables (other than the lack of a standard) - mid-way between plain plastic sheathed and SWA - with many but not all of the benefits but with savings (esp. installation convenience). One attraction of CY/SY is that it's far more readily available with larger number of cores than most other cable types. By gut feel is that the braid isn't going to fare any worse under fault conditions than the aluminium foil of BS 8436 cables - and they're OK standards wise for BS 7671 use (within certain limitations of course).

I'm sure I've something in my long term memory about the HSE recommending CY/SY for extension leads (with the braid earthed of course) in environments where ordinary flexes may be damaged - providing some attempt at ADS while retaining the necessary flexibility. Something that neither ordinary flex or SWA would really be suitable for.

The obvious solution is for the cable manufacturers and standards bods to pull their finger out and come up with the suitable standard, so we could all know what we're dealing with.

     - Andy.

fair do's Andy

there is more commentary on needed/wanted standards etc

https://www.basec.org.uk/news/2019/4/25/new-testing-certification-scheme-yy-sy-cy-control-cables/

In your view, does/could the braid qualify as 'mechanical protection' in the case of BS7671  like SWA would/does (arguably)  e.g. if buried in fabric < 50mm without RCD ?

Looking at some examples of the stuff, it appears 'no' to the above, as it looks more like screening on some coax  ... though one can appreciate there is an increase in strength from the braid for other cases where not buried or as a 'flex/extension'

Is the braid suitable to act as a protective conductor, as if not then it could only be for just the [increased to some degree] mechanical protection; but is it ever an exposed conductive part  required to be earthed ?

One supposes not to the above so long as it cannot be touched.

Indeed, metal capping is not ever earthed is it (or is it !).

Thank you

Habs

just to add, this comment was read on a website, "...I have had a direct conversation with the IET about this very topic recently. They confirmed to me that they are not telling electricians not to use it - but they are warning them that the specifier is liable for any associated costs should there be a fault with the cable. As SY does not have a VDE, BASEC or HAR standard, this means the installer is potentially specifying the cable at their own risk. However; the specifier is not liable if the manufacturer of the SY cable has their own quality guarantees. For instance; every cable that Lapp supplies is covered by our 18 month product warranty (t&c’s apply) and £25m product liability. Hence, should their be an associated cost due to the failure of our cable - Lapp are liable for this cost, not the specifier/installer. The IET are warning installers to ensure that their cables are “sustainability sourced” for want of a better word - not telling them that SY must never be used - and quite rightly, when you consider the amount of SY cable in the marketplace that does not have any quality guarantee. ..."

other commentary - 'interesting':

uk.prysmiangroup.com/.../sy-yy-cy-cable

other commentary - 'interesting':

uk.prysmiangroup.com/.../sy-yy-cy-cable

That seems pretty balanced to me.

If there were a particular use for this cable for which other cables were not suitable, would a standard not have been created?

a rhetorical question perhaps  :-)

is it unsafe though to use ... likely not in many cases (or that seems to be the prevailing implication), but going 'off book' on an install requires the designer/specifier take responsibility for making the choice (why etc ) and hopefully to record such (especially if a  deviation from the norm).

when it comes to inspections, is it really an issue though if it is used and what is a fair observation of it ... however if a non-standard is used how can it be assessed and what against and so on  ...