More chance of mechanical damage for the circuits within reach. As I said, it's a guess.
Mains smoke and heat detectors
- Thread starter foxhole
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Fair enough - but as IU asked, in what sense is the fixed wiring of a non-lighting circuit (usually) more "within reach" than is the fixed wiring of a lighting circuit?
Kind Regards, John
Well in that case so is everything, and I could use 1mm² for any circuit I choose and say "yes, it may very well be supplying smoke detectors, a couple of fans, a shaver socket and a TV, but they are all out of scope, and therefore irrelevant, and therefore it is a lighting circuit."
Please get a grip stillp, and wake up and smell the coffee. The unignorable point is that the term "power circuit" means absolutely nothing. IOW it is meaningless. It is impossible to comply with a something meaningless.
But what IS a "power circuit"? How can the designer consider whether his circuit is, or is not, something undefined?
From memory BS7671:2008 incorporating Amendment No. 1 (2011).
For fixed cables protected by the fabric of the building?
Does anyone have the actual wording? My old book is not accessible for inspection.
It's not really 'wording' but more a change in structure of Table 52.3. In the original BS7671:2008 (red), there was just a single row in the table for "lighting and power circuits', for which the mnimum CSA was 1.0mm² copper (or 16mm² aluminium). In Amd1 (green), this split into two rows, one for 'lighting circuits' and the other for 'power circuits'. the minimum CSA for 'lighting circuits' remained as 1.0mm² copper, bit the one for 'power circuits' was then stated as 1.5mm² copper. The table remains unchanged from that in Amd3 (yellow).
Kind Regards, John
Ah, so is that the origin of that confusing Note 5 in the IEC table?
Well, it could, if they forget to remove one note when they inserted an updated one - but it would seem pretty improbable that "Note 5" came chronologically before "Note 4"
Kind Regards, John
Unless it also contained a definition of "power circuit" it is simply impossible for 1.0 mm² to be declared unsuitable for them, for without a definition they simply do not exist.
So it was nonsense then.
With no definition for it, the table might as well have said "lighting and fnarglebargle circuits"
Well, a lot less nonsense than it became after the "split", since when the two were lumped together, one did not need definitions to distinguish between a 'lighting circuit' (which supplied power to lights) and a 'power circuit'. At that time, I think most people would have happily taken "lighting and power circuits" to refer to all circuits designed to supply significant power to loads (i.e. excluding only control/signalling circuits etc.).
Kind Regards, John
It's certainly odd, but at least it seems to tie in - Somehow! How they got that odd wording in Note 5 and what it's actually supposed to mean is still a mystery though.Well, it could, if they forget to remove one note when they inserted an updated one - but it would seem pretty improbable that "Note 5" came chronologically before "Note 4"
I don't know about the installations with which you're familiar, but usually lighting is overhead, whereas socket-outlets, CCUs, switch-disconnectors supplying machines, etc, are not overhead.
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