Are installation methods 100, 101, 102 & 103 Reference methods?

[sxdave]

I am interested in opinions on the following. Looking at GN3, page 126 the example of a Generic Schedule of test results lists the reference method as 100. When I look at the OSG Table 7.1(ii) on page 74 it lists A, B, C, 100, 101, 102 & 103 as 'installation reference methods'. However when I refer to BS7671 section 7.1 the reference methods are A through to G. Also Section 7, Table 4A2 for methods 100 to 103 (page 390) redirects to Table 4D5 which labels methods 100 to 103 simply as 'methods' not reference methods. So my conclusion is that GN3 and OSG do not comply with BS7671.

 

[timhoward]

I don't have any intention of getting into a long discussion but draw attention to a few quick things.
7.1 "The reference methods are those methods of installation for which the current carrying capacity has been determined by test or calculation".
Table 4D5 does exactly that task too.

Ultimately all that matters is BS7671. As the OSG seeks to provide a condensed guide to a complex document it inevitably makes generalisations and simplifies things.
GN3's focus is I&T. Part of inspecting is determining if the OCPD is appropriate for the cable and installation method. Recording the method, whether A,B or 103 is simply showing your working.

The point of the system is to provide the most efficient way to match method/environment and cable type and end up at a number. A-G can be applied to most cable types and was deemed sufficient. I suspect that the amount of T&E out there and the variation in performance in frequently used environments caused the powers that be to create some special tables for it. For example the depth of insulation is the difference between complying with the 20A ring final circuit reg or not.

I don't really see a problem here.