How closely does BS 7671 track IEC 60364?

I'm not sure about 521 in particular, but in general I think it's safe to assume that there must be some very significant differences, at least in places. Just compare other standards that should equally be based on 60364 - e.g. the French NFC 15-100 or German DIN VDE 0100. Ring circuits, bare c.p.c.s, reduced c.s.a. c.p.c.s., steel CUs to mention just a few of the more obvious ones.


I suspect that what we see in the DPCs are often based on IEC or CENELEC work, but as the published versions often differ again (at least in wording if not in intent) then there must be some room for UK deviation in those cases too.


I'm sure there must be some mechanism for feeding back to CENELEC and IEC, but whether it's based on BS 7671 or by some separate committee I don't know.


    - Andy.

The picture is slightly more complicated than considering IEC 60364 series.


Because of BSI's membership of CENELEC, BS 7671 must align with HD 60364-series.


A HD (Harmonized Document) is produced in the same way as an EN (Euro Norm).

• In the case of an EN, it is taken verbatim into national standards - so BS EN 62368-1 should be identical to VDE EN 62368-1. Any national variations in an EN are agreed before the EN is published. We call those "SNCs", or "Special National Conditions".

• In the case of HDs, the technical intent of the HD must be adopted by national standards, but the actual wording and additional national requirements can be added. However, if a national standard does not want to adopt the technical intent of a particular requirement in the HD, in the same way SNCs are agreed before the HD is published.

In aligning with HD 60364, the provisions in BS 7671 must adopt the minimum technical intent of the relevant parts of the standard.

Occasionally, the wording of requirements in "international English" doesn't really lend itself to direct implementation in BS 7671 (yes, it really can get more confusing that it is already), so even where the requirements of a Regulation are the same, the wording may well be slightly different in BS 7671.


So where does IEC 60364 series fit in with that? Well, that's published in IEC (the electrotechnical side of ISO). Parts of IEC 60364 may be started by IEC project work, or offered up from CENELEC if CENELEC see the need to develop a new part first - however, these days usually CENELEC members would begin an IEC project first, and then CENELEC will decide whether to adopt that part. National variations are agreed when IEC documents are being prepared and commented on - in IEC these are termed "SCNs" (In Some Countries Notes)


When a part of IEC 60364 is updated, CENELEC committees decide whether to adopt that amendment (a process called "parallel vote"), or whether amendments are needed for CENELEC countries, and at this point HD 60364-x-yyy might differ slightly from IEC 60364-x-yyy. SCNs are transposed to SNCs at this point also, and reaffirmed.


So occasionally, you will see new technical intent in BS 7671 first, before it is adopted internationally, and at other times new intent will come from CENELEC and/or IEC.



BSI do publish the international standards for public comment in the same way as BS 7671, before they get adopted, so it's all an open process, even if it seems a bit daunting at first after reading my missive above in this post.

Thanks for that, Graham.

So, is this right:

BS 7671 very closely tracks HD 60364, less SNCs and plus local additions (e.g. .201's).

HD 60364 less closely tracks IEC 60364, with SCNs allowing divergence.

In amendments, the IET may add extra local stuff to BS 7671, but can't take stuff away without prior agreement. Such changes can later  be suggested to the CENELEC committees who may pass them to the IEC who may or may not adopt them

Very roughly - although bear in mind:

• "closely tracks" doesn't mean "worded the same".

• As sections in BS 7671 are revised, we are working towards using the .101 and .201 numbering scheme, but it's not made its way to all sections at the moment.

• When we talk about "stuff" being added but not taken away, it's best to use the term "technical intent", because this covers a number of ills. There may be an odd case where, for example, a particular Regulation in the HD does not appear in BS 7671 - but that doesn't mean the technical intent is not implemented  - for example, if something in a Part 7 section repeats one of the general rules, then, to avoid repetition in BS 7671, the Regulation may be omitted.