SY Cable and BS 7671
Regulation 133.1.1 Selection of Electrical Equipment –
Every item of equipment shall comply with the appropriate British or Harmonized Standard. In the absence of such a standard, reference shall be made to appropriate International (IEC) or the standard or the appropriate standard of another country.
For further information see page 26 of BS 7671.
Regulation 511.1 Compliance with Standards (Note 2) –
The use of foreign national standards not based on an IEC Standard, and/or not compatible with the safety provisions of BS 7671, is not recommended.
On-Site Guide Section 7.9 Installation of non-standard cables –
For the purpose of this Guidance Publication and to ensure compliance with BS 7671, the installation and use of non-standard cables, such as SY, CY and YY cables is discouraged.
One cable manufacturer has issued a statement in relation to the use of SY, CY and YY cables in UK-based fixed installations, to view this statement see the links at the bottom of this post.
We found another cable manufacturer who say they do not manufacture SY, CY or YY cable types as they do not comply with any manufacturing standard, see the links at the bottom of this post for further details.
If an SY cable is used in an installation which is subject to BS 7671 then a deviation should be noted on the electrical installation certificate to note as such. In addition a comprehensive risk assessment should also be attached to the electrical certificate, the risk assessment should include the name of the person who is taking full responsibility for the installation and use of such a cable.
An Electrician might to refuse to install an SY cable in an installation which is covered by BS 7671, based on the current guidance.