Mains smoke and heat detectors

[stillp]

Appliances are outside the scope of BS7671.

 

[ban-all-sheds]

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'?

Well - legislation is a different matter. However much a court's decision means "it depends", I am confident in saying that one guaranteed bit of consistency would be rejection of a defence along the lines of "I ignored it, m'lud, because I don't I should have to pay any attention to badly worded legislation which doesn't make sense."

But a technical regulation with no safety facets? DKOF. And my attitude is (at least partly) informed by the belief that engineers who write imprecise rubbish like that genuinely deserve a metaphorical poke in the eye for doing it.

 

[ban-all-sheds]

Appliances are outside the scope of BS7671.

Not sure why that matters.

 

[EFLImpudence]

I think the safest bet is to use 16mm² aluminium cable - that is the same for both lighting and power circuits.

 

[stillp]

Because your fan, with a plug on, is outside the scope of the standard and is irrelevant to the purpose of the circuit as designed.

 

[JohnW2]

Appliances are outside the scope of BS7671.

They are. However, it still begs the question as to whether or not a circuit supplying 2A or 5A BS 546 sockets, originally "intended" to be used for lights, qualifies as a 'lighting circuit', since equipment other than lighting could be plugged into the sockets.

Kind Regards, John

 

[stillp]

I think the safest bet is to use 16mm² aluminium cable - that is the same for both lighting and power circuits.

 

[JohnW2]

Well - legislation is a different matter. However much a court's decision means "it depends", I am confident in saying that one guaranteed bit of consistency would be rejection of a defence along the lines of "I ignored it, m'lud, because I don't I should have to pay any attention to badly worded legislation which doesn't make sense."

Are you sure about that? A court might not like someone arguing that "they should not pay attention to" any legislation, badly worded or not. However, if their defence was that that had not been able to comply with (badly worded) legislation, because they simply couldn't understand it, might a (sensible) court not agree that no-one could be expected to comply with a law which "no reasonable man could be expected to understand"?

Kind Regards, John

 

[stillp]

Appliances are outside the scope of BS7671.

They are. However, it still begs the question as to whether or not a circuit supplying 2A or 5A BS 546 sockets, originally "intended" to be used for lights, qualifies as a 'lighting circuit', since equipment other than lighting could be plugged into the sockets.

Kind Regards, John

Does your house meet the requirements for a motorway, just in case somebody changes it from the designer's intent?

 

[stillp]

However, if their defence was that that had not been able to comply with (badly worded) legislation, because they simply couldn't understand it, might a (sensible) court not agree that no-one could be expected to comply with a law which "no reasonable man could be expected to understand"?

I thought it was agreed that it is perfectly possible to comply with the table, even though the reasons for its provisions are not apparent?

 

[PBC_1966]

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).

Precisely. If they've decided that 1.5 should be the minimum size from now on for reasons of increased mechanical strength, it makes no sense to then say that 1.0 sq. mm is still adequate for some specific reason. And as far as the cable is concerned, it makes absolutely no difference if it's feeding X amps' worth of lighting or X amps' worth of some other load.

I thought it was agreed that it is perfectly possible to comply with the table, even though the reasons for its provisions are not apparent?

In the case of fixed cables (not flexible) it would clearly be possible to be sure of complying by using 1.5 as a minimum for everything. But that's obviously not what is required by the provisions of that table since it's permitting 1.0 to be used in some cases.

What do you think it actually means by "lighting circuit" and "power circuit," and for that matter what do you think those cryptic notes in the IEC version are saying?

 

[stillp]

FWIW I think that it means "A circuit that the designer considered to be a lighting circuit" and "A circuit that the designer considered to be a power circuit". The notes don't seem cryptic, although they could be better worded.

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

Anyone?

 

[skenk]

Minimum CSA of 1mm is given for power circuits in red book 17th edition 2008 (p105 table 52.3) so I think it came in with amd1 to the 17th as I don't think it's new with amd2?

 

[PBC_1966]

FWIW I think that it means "A circuit that the designer considered to be a lighting circuit" and "A circuit that the designer considered to be a power circuit".

Doesn't that rather make the regulation quite pointless then? And I have to keep going back to this, but as there doesn't seem to be anything which says something like "For the purposes of this regulation a power circuit is deemed to be....." then I dont see how a circuit which supplies nothing but lights and is therefore quite clearly a "lighting circuit" is not at the same time a "power circuit."

If there was a statement such as this -

For the purposes of this regulation a circuit in which the number of outlets for lighting fixtures is greater than the number of outlets for other loads shall be considered to be a lighting circuit, and any other circuit shall be considered to be a power circuit

- then the intent would be much clearer, even if from a technical point of view it still made absolutely no sense.

The notes don't seem cryptic, although they could be better worded.

So what do you think they actually mean?

 

[stillp]

I have to keep going back to this

No, you don't have to!

The notes don't seem cryptic, although they could be better worded.

So what do you think they actually mean?

They're simple statements. Which word(s) don't you understand?