"Hugo Nebula" abuse@localhost wrote in message
...
On Sat, 30 Jun 2007 16:23:30 +0100, a particular chimpanzee, "Doctor
Drivel" randomly hit the keyboard and produced:

The building regulations are law. If they point to the 17th, then that is
law too. British Standards are recommendations only and you don't need to
follow - if the Building regs point to a BS it is law in that context.

Not quite. The Building Regulations are law, but in this case the
requirement Part P of Schedule 1 to the Regulations says, "reasonable
provision shall be made in the design, installation, inspection and
testing of electrical installations in order to protect persons from
fire or injury". That is the only legal requirement.

The Approved Documents details _how_ the requirement can be met, and
AD P references BS7671: 2001 Chapter 13. The preamble to the Approved
Document, however, also says, "however, if [a named standard] has been
revised or updated by the issuing standards body, the new version may
be used as a source of guidance provided it continues to address the
relevant requirements of the Regulations". If the 17th edition has
been published as a 'proper' standard, then it can be used as
guidance.

You should also remember that the wiring regs are the /minimum/ standard and
a competent person may well do it a different way that is safer.
The basic rule is that the regulations are there to guide the people that
don't know how to do things which is why they have clauses like "shown by
calculation" in them so that people can vary them if they wish.
I personally have never wired 30/32A rings in 2.5mm as in my judgement the
cable should *always* be larger than the breaker, its not to the average
electricians understanding of the "regs" but it is safer, the cost saving is
minimal these days.