j,
I see the problem, but the OSG is after all a Guide. I imagine that most of us ignore the 'boring' bits at the start like the introduction which defines the 'scope' and applicability; being people that like to do things we jump straight to the sections which refer to that which we are doing at the time. If you have a copy, take a look at page 12:
'This Guide is not a replacement for BS 7671 which should always be consulted.'
The standard is not what the OSG says but what does BS 7671 say. Furthermore, OSG page 11 section 1.1 Scope states 'This Guide is restricted to installations:' and then lists conditions. The OSG is subordinate to BS 7671 which does not in itself cover every electrical installation. In the same way that the cable is protected by a suitable protective device, BS 7671 could be condsidered to be the 'umbrella' under which the OSG sits. OSG page 7 states: 'The Guide ... does not ensure compliance with BS 7671. In turn, 'It cannot be guaranteed that BS 7671 complies with all relevant statutory regulations.' It is the statutory regulations that have legal power and against which we will be judged if called before a court of law. The approved codes of practice - BS 7671 and others including the OSG, if we have followed them, are our defence because they are 'approved' but we must know how and where to apply them. However, the OSG because it has to cover a variety of situations, has to err on the side of caution in order to safely cover differing requirements. Knowing and understanding the Regs will enable tailoring of a solution to specific circumstances and therefore is more materials efficient but it comes with a time penalty and possibly different costs; in learning and understanding the details of how and why things work and to gain and maintain confidence in your own decision making skills.
The ultimate question is who is signing off the work ... would you suspend your life as if by a thread from your work?
Hope this helps.
GB
