Mains smoke and heat detectors

[PBC_1966]

Yes, but what is the "power circuit" category?

A circuit that isn't a lighting circuit? (Other than the other categories that we are not discussing).

That would seem to be what the table is suggesting, given that it divides wiring into "lighting" and "power" categories. Which brings us back to the question of what is a lighting circuit?

As several of us have asked already, is it a circuit which supplies any light, regardless of what else it might supply? Is it a circuit which supplies mostly lights, by number or by power? A circuit which supplies nothing but lights?

Don't you think it's rather unacceptable for a standard to demand compliance with something based upon two different categories of wiring without giving any sort of clear definition as to what the names applied to those two categories are supposed to mean?

What is going on here is that it is quite simply impossible to comply with nonsense.

Of course compliance is possible. If you find the decision too difficult, just use 1.5 mm².

Yes, clearly using 1.5 sq. mm as a minimum for everything would result in compliance, but it's obvious that's not what was intended, otherwise it would not permit 1.0 sq. mm for "lighting circuits."

How would somebody wanting, for whatever reason, to use the minimum size specified by the standard for each circuit be able to understand what those minima are from reading that table?

 

[stillp]

Maybe the 1.0 mm² is only in there as a concession for those countries in which it was historically used for lighting circuits. As I've said, I don't know. I was asked to offer a guess, and I'm beginning to wish that I hadn't acceded to that request.
No, I don't think it is unacceptable. I do think the requirements of the table could be worded more clearly.

 

[stillp]

Sorry, but this idea just makes no sense.

All right, suggest an alternative interpretation then.

 

[EFLImpudence]

Delete Table 52.3

Rely on the rest of the regulations regarding cable selection.

 

[PBC_1966]

All right, suggest an alternative interpretation then.

That's the problem - What interpretation is possible which makes any sort of technical sense regarding current-carrying capacity of the cables, voltage drop, mechanical considerations etc?

Yes, seeing this table and the notes in the IEC version I certainly don't disagree that this "halfway house" was probably intended as some sort of temporary concession to the U.K., no doubt to be followed by a complete removal of 1.0 sq. mm in the future. But for a standard which is setting requirements which must be followed in order to claim compliance with that standard, don't you think it's rather a poor show to produce a regulation which uses terms which are not defined, and which you have yourself suggested can be used any way the designer intends them to be applied?

If, as you indicated earlier, you feel that a lighting circuit is whatever the designer of the installation intends or deems to be a lighting circuit, then what exactly is this regulation requiring as a minimum and why does it need to exist in the first place?

If I were to run 1.0 sq. mm to a couple of BS546 sockets and say "I intend them to be used for lights so as far as I'm concerned this is a lighting circuit," would that be complying with the requirements for a "lighting circuit" in table 52.3, even though I've not connected any actual lights and those sockets could be used for almost any small appliance?

 

[stillp]

If I were to run 1.0 sq. mm to a couple of BS546 sockets and say "I intend them to be used for lights so as far as I'm concerned this is a lighting circuit," would that be complying with the requirements for a "lighting circuit" in table 52.3, even though I've not connected any actual lights and those sockets could be used for almost any small appliance?

What are BS 546 sockets used for? I've only seen lights and a clock connected to them. If the circuit was wired in 1.0 mm², and protected at 6 A, and the designer did not have any reason to believe it would be used for any other purpose, then that would be a lighting circuit to me.

 

[stillp]

I'm surprised nobody has asked yet for a definition of "Signalling and control circuits", and suggested that they could wire a ring final in 0.5 mm² if they used a couple of those powerline networking adaptors!

The only sort of person who would do that would be one who was so unfamiliar with BS 7671 that they were unaware of the explicit requirements for ring finals (for BS 1363 accessories).

What are you trying to say BAS? Are only BS1363 accessories allowed on a RFC now? I must have missed that.

 

[PBC_1966]

What are BS 546 sockets used for? I've only seen lights and a clock connected to them. If the circuit was wired in 1.0 mm², and protected at 6 A, and the designer did not have any reason to believe it would be used for any other purpose, then that would be a lighting circuit to me.

What if designer has reason to believe they might well be used for something else? Or if he flat-out knows they are intended for something else? Would you still consider it to be a lighting circuit?

By the way, back in England I used BS546 5A sockets extensively for my electronics workbench for test equipment - Neater for rows of outlets for numerous pieces of relatively low-power equipment.

 

[JohnW2]

I agree. For example, as per the question I just asked stillp, what if, instead of what is about to happen (itself undefined), Amd3 of BS7671 had included a requirement that only CUs manufactured from ferrous metal were allowed in 'large houses' - without 'large house' being defined?

That would not be a problem as the whole of 421.1.201 is in the "must be ignored" category because it is impossible to comply with, and will always be so until "non-flammable" is defined.

Did you not read my words that you have just quoted? It's for that very reason that I was asking about the situation if, instead of what is about to happen (implementation of the existing 421.1.201, as written, with 'non-combustible' etc.) the Amendment had explicitly specified that ferrous metal CUs had to be used for 'large houses'.

Kind Regards, John

 

[JohnW2]

Would you write a regulation which just says that the smaller cable should not be surface run below a height of whatever, or ...

So I wonder if stillp thinks that 1.0 mm² is not acceptable for wiring 'under-cabinet lights' etc.?

Kind Regards, John

 

[stillp]

What if designer has reason to believe they might well be used for something else? Or if he flat-out knows they are intended for something else? Would you still consider it to be a lighting circuit?

If he know they are intended for something else, then he knows it is not a lighting circuit.

 

[PBC_1966]

If he know they are intended for something else, then he knows it is not a lighting circuit.

So in each case you have the same sockets, in the same location, fed from the same protective device, using the same type of cable installed by the same method and following the same route. What possible technical reason is there for saying that if the designer knows/believes that the sockets will be used only for lights then it's acceptable to use 1.0 sq. mm cable, but he knows/believes they'll be used for something else it needs to be 1.5 sq. mm?

 

[JohnW2]

So in each case you have the same sockets, in the same location, fed from the same protective device, using the same type of cable installed by the same method and following the same route. What possible technical reason is there for saying that if the designer knows/believes that the sockets will be used only for lights then it's acceptable to use 1.0 sq. mm cable, but he knows/believes they'll be used for something else it needs to be 1.5 sq. mm?

Indeed. It just doesn't make sense. Whatever the reason/thinking behind it, whether 'susceptbility to mechanical damage' or whatever, it just makes no apparent sense that the requirements should differ for an identical circuit according to what one knew/thought would/could be plugged into the sockets.

Kind Regards, John

 

[ban-all-sheds]

Maybe the 1.0 mm² is only in there as a concession for those countries in which it was historically used for lighting circuits.

It was also historically used for "power circuits" here.

As I've said, I don't know. I was asked to offer a guess, and I'm beginning to wish that I hadn't acceded to that request.

Your guesswork is not the problem. If I had to guess I would say that's what making you uncomfortable is your decision to defend an indefensible regulation.

No, I don't think it is unacceptable.

What you are saying there is that you think it is acceptable for a standard to demand compliance with something based upon two different categories of wiring without giving any sort of clear definition as to what the names applied to those two categories are supposed to mean.

I stand by my earlier observation - with such a casual attitude to engineering rigour, accuracy, and precision you should not be allowed anywhere near the writing or QAing of standards.

 

[ban-all-sheds]

If, as you indicated earlier, you feel that a lighting circuit is whatever the designer of the installation intends or deems to be a lighting circuit, then what exactly is this regulation requiring as a minimum and why does it need to exist in the first place?

Can the designer do that?

Have we established that a lighting circuit is one which supplies only lights, and nothing else?

If I were to run 1.0 sq. mm to a couple of BS546 sockets and say "I intend them to be used for lights so as far as I'm concerned this is a lighting circuit," would that be complying with the requirements for a "lighting circuit" in table 52.3, even though I've not connected any actual lights and those sockets could be used for almost any small appliance?

What if you ran 1.0mm² to BS 1363 sockets and said "I intend them to be used for lights so as far as I'm concerned this is a lighting circuit" ?