Mains smoke and heat detectors

[stillp]

I should have added that the table is preceded by this sentence:

524.1 For mechanical reasons, the cross-sectional area of line conductors in a.c. circuits
and of live conductors in d.c. circuits shall be not less than the values given in Table 52.2.

 

[JohnW2]

NOTE 4 In the UK, 1,0mm2 cable is allowed for use in lighting circuits.

That is, indeed, what the infamous table in BS7671 says, but ...

NOTE 5 In the UK 1,0 mm2 copper cable is allowed for fixed installations utilizing cables and insulated conductors for power and lighting circuits.

... what's that all about?

Kind Regards, John

 

[stillp]

Somebody forgot to update the basic standard?
I no longer have previous editions of BS 7671. When was 1.0 mm² declared unsuitable for power circuits in BS 7671?

 

[EFLImpudence]

Somebody forgot to update the basic standard?

Perhaps it's BS7671 that is a misprint.

I no longer have previous editions of BS 7671. When was 1.0 mm² declared unsuitable for power circuits in BS 7671?

What about 0.75mm² with flexible cable?

 

[JohnW2]

Somebody forgot to update the basic standard? I no longer have previous editions of BS 7671. When was 1.0 mm² declared unsuitable for power circuits in BS 7671?

Nor do I, but hopefully someone can tell us about the history. I suppose my real point was to wonder what was the point of Note 4, given Note 5 - unless they were saying that in the UK 1.0 mm² cables which had conductors which were not copper and/or were not insulated were allowed for lighting circuits Maybe some of the apparent nonsense in BS7671 has been inherited from nonsense in this other Standard!

Kind Regards, John

 

[stillp]

What about 0.75mm² with flexible cable?

What about it? It's allowed in IEC 60364-5-52, if that was the question.

 

[PBC_1966]

Yes, it's based on Table 52.2 of IEC 60364-5-52. I can't copy the table here, but it includes the following Notes:

NOTE 4 In the UK, 1,0mm2 cable is allowed for use in lighting circuits.
NOTE 5 In the UK 1,0 mm2 copper cable is allowed for fixed installations utilizing cables and insulated conductors for power and lighting circuits.

And does this IEC standard define what is actually meant by "lighting circuit" and "power circuit" in clear terms?

 

[EFLImpudence]

What about 0.75mm² with flexible cable?

What about it? It's allowed in IEC 60364-5-52, if that was the question.

You seem to be being deliberately obtuse in this matter.

So, 1.5mm² or even 1mm² is not the minimum required for either power or lighting circuits - and yet you maintain table 52.3 is reasonable and understandable.

 

[ban-all-sheds]

Yes, it's based on Table 52.2 of IEC 60364-5-52. I can't copy the table here, but it includes the following Notes:

NOTE 4 In the UK, 1,0mm2 cable is allowed for use in lighting circuits.
NOTE 5 In the UK 1,0 mm2 copper cable is allowed for fixed installations utilizing cables and insulated conductors for power and lighting circuits.

And does this IEC standard define what is actually meant by "lighting circuit" and "power circuit" in clear terms?

My immediate thought was to ask the same Q.

If the terms are not defined then the requirement is meaningless. In the plain, everyday sense - if they do not define how a "power circuit" differs from a "lighting circuit" then the term "power circuit" means nothing.

And anybody who writes technical regulations which are meaningless MUST be ignored, because people like that, and the meaningless stuff they write, MUST NOT be allowed to exist (regulation-wise).

 

[JohnW2]

And anybody who writes technical regulations which are meaningless MUST be ignored, because people like that, and the meaningless stuff they write, MUST NOT be allowed to exist (regulation-wise).

What about regulations (or legislation) which are so vague that one would probably be hard-pressed to find two people who interpreted them identically - should they also be 'ignored' since, given countless possible interpretations/opinions, they are also effectively 'meaningless'?

Kind Regards, John

 

[PBC_1966]

NOTE 4 In the UK, 1,0mm2 cable is allowed for use in lighting circuits.
NOTE 5 In the UK 1,0 mm2 copper cable is allowed for fixed installations utilizing cables and insulated conductors for power and lighting circuits.

I suppose my real point was to wonder what was the point of Note 4, given Note 5 - unless they were saying that in the UK 1.0 mm² cables which had conductors which were not copper and/or were not insulated were allowed for lighting circuits

I wonder if the phrase "cables and insulated conductors" in note 5 is meant to refer to composite cables such as British T&E, and to insulated single conductors as would be drawn into conduit? Not that the result of interpreting it that way makes any sense.

It strikes me that these notes are likely some combination of (a) misunderstanding about the U.K. standard, (b) a mistranslation into some other language and back to English again, and/or (c) notes having been added to account for changes in U.K. regs. and other notes not having been deleted or amended accordingly.

And we still have no idea what "lighting circuit" and "power circuit" are actually supposed to mean.

 

[PBC_1966]

I should have added that the table is preceded by this sentence:

524.1 For mechanical reasons, the cross-sectional area of line conductors in a.c. circuits
and of live conductors in d.c. circuits shall be not less than the values given in Table 52.2.

So it sounds as though the IEC is specifying 1.5 sq. mm minimum for everything "for mechanical reasons," but noting continued use of 1.0 sq. mm in the U.K. in some cases, the latter being almost impossible to work out from the confusing notes.

But I note it refers to the size of line condutors in a.c. circuits and of live conductors of d.c. circuits, rather than all conductors (including earth) or of all current-carrying conductors. What are the IEC definitions of an a.c. line conductor and a d.c. live conductor? (Since I wouldn't assume they match up with what I or anyone else here might take those terms to mean.)

 

[JohnW2]

And we still have no idea what "lighting circuit" and "power circuit" are actually supposed to mean.

Quite so - and, even if we did know, I think I would struggle to understand why there should be different minimum CSA sizes for the two.

I could just about understand a 'blanket' ban on 1mm² for anything ('for mechanical reasons'), and the CSA requirement will obviously depend on the load and OPD, but if (at least in UK) 1mm² is deemed (electrically and mechanically) adequate for a 'lighting circuit' (however defined) why on earth should it not be also acceptable for a 'non-lighting circuit' of the same or lower current (e..g. dedicated circuit for alarm or boiler).

Kind Regards, John

 

[stillp]

What about 0.75mm² with flexible cable?

What about it? It's allowed in IEC 60364-5-52, if that was the question.

You seem to be being deliberately obtuse in this matter.

So, 1.5mm² or even 1mm² is not the minimum required for either power or lighting circuits - and yet you maintain table 52.3 is reasonable and understandable.

No, I'm not being obtuse. You've already said that it is possible to comply with the table. I haven't said that the wording is not in need of improvement.

 

[ban-all-sheds]

What about a lighting circuit with BS 546 sockets for floor or table lamps, and then you buy a fan and decide to put a BS 546 plug on it. Does possession of such an appliance change the circuit, or only using it?