but who decided the abstract figure and on what basis? It's a bit like saying any earth rod over 500 Ohms is not good enough or is that 200 Ohms now - I've forgotten!
You need to work the figures backwards..
AND.. remember the extracts quoted above are from the "INITIAL INSPECTION AND TESTING" of a NEW installation part of GN3...
(e.g. NOT periodic inspection on an old existing installation section..)
so if a new installation Global =20meg.. and you have:-
6 circuits this equals average 120Meg per circuit, Or one low around 30Meg + rest high
8 circuits this equals average 160Meg per circuit, Or one low around 30Meg + rest high
10 circuits this equals average 200Meg per circuit, Or one low around 30Meg + rest high
12 circuits this equals average 240Meg per circuit, Or one low around 30Meg + rest high
14 circuits this equals average 280Meg per circuit, Or one low around 30Meg + rest high
etc..
etc..
etc..
Which..
For a brand new installation IMHO would suggest some dodgy installation work somewhere.?
AFAIK
the 20Meg Global is another rule-of-thumb to indicate if you need to stop and do further investigations.
However...
Personally I still like to know the exact individual circuit figures as well so I can calc OR measure Global!
Guinness