Mains Smoke Alarm

[ban-all-sheds]

Your point being..... ?

 

[PBC_1966]

My point being in relation to this comment -

So, in conclusion, there is nothing to suggest a harmonised black is the best colour to use as a neutral in a 3 core+E cable, so only silly people would choose to do this.

- That it would seem rather silly not to use the black in the 3-wire d.c. application. And if it's all right in that application, why not with the a.c. live/switched live/neutral scenario?

 

[EFLImpudence]

Or - That when only one out of the three wires is the right color for the application someone with no authority has spuriously deemed that only one of the remaining two may be identified with blue sleeving.

 

[ban-all-sheds]

My point being .. That it would seem rather silly not to use the black in the 3-wire d.c. application.

Yes, but that's not because it's black, it's because it's neither brown nor grey. It would be equally silly not to use the purple core in a brown/purple/grey cable, or the orange and pink polka-dot core in a brown/orange and pink polka-dot/grey cable for exactly the same reason.

And if it's all right in that application, why not with the a.c. live/switched live/neutral scenario?

Because there's no equivalent standard for the colours for line and switched line to the one for the colours for + and - in a 3-wire DC cable.

 

[PBC_1966]

Yes, but that's not because it's black, it's because it's neither brown nor grey.

Which is exactly the same position as with the L/SwL/N scenario: You're sleeving the black & grey not because they're black & grey but because they not brown & blue. Or with a 3-core SWA cable being used for L/N/E, you're sleeving them because they're not blue & green/yellow.

Because there's no equivalent standard for the colours for line and switched line to the one for the colours for + and - in a 3-wire DC cable.

Isn't there? They're both required to be brown now, just as they were both required to be red before. Although personally I never saw much point in that in a 2-wire single-phase setting, since you knew that yellow & blue were not different phases or poles but merely some other live, typically a switched one.

Or - That when only one out of the three wires is the right color for the application someone with no authority has spuriously deemed that only one of the remaining two may be identified with blue sleeving.

Precisely. You have two wires which are not of the appropriate color, so it's pretty much an arbitrary choice as to which you choose to sleeve brown and which blue (or which blue and which green/yellow etc.). And like it or not, black is associated with neutral in Britain through long usage and is still going to retain that association to some degree for many decades to come due to the miles of "old" cable still in use.

The specific point I was trying to address is that I don't in any way see the logic of making the jump from saying that red/yellow/blue have become brown/black/grey respectively as far as the colors for 3-phase work are concerned, 99.9% of people used to use blue (sleeved black) as the neutral in a red/yellow/blue cable, therefore grey (sleeved blue) should be the natural choice for neutral in the new scheme and that to use black is "silly."

 

[EFLImpudence]

I'm a bit confused by the last post. You seemed to change your mind.

Anyway -

therefore grey (sleeved blue) should be the natural choice for neutral in the new scheme and that to use black is "silly."

It's not silly; it either doesn't matter, or:

What about my point about disconnection when penetrated or damaged?

Brown. Black... G/Y...Grey
.Live...Neutral..CPC...Live
as opposed to:
.Live.....Live.....CPC..Neutral

 

[PBC_1966]

I'm a bit confused by the last post. You seemed to change your mind.

Not at all. I said that I do not see the logic in saying that it's "silly" to use black for the neutral just because of red/yellow/blue becoming brown/black/grey respectively for 3-phase.

What about my point about disconnection when penetrated or damaged?

Brown. Black... G/Y...Grey
.Live...Neutral..CPC...Live
as opposed to:
.Live.....Live.....CPC..Neutral

I suppose you could argue there's a minimal benefit, but I can't see it being of particular signifance.

What about using the cable as a drop to a 2-way switch, or a 2-gang 1-way with feed and two switched returns? Either way you end up with live - live - earth - live.

 

[ban-all-sheds]

I said that I do not see the logic in saying that it's "silly" to use black for the neutral just because of red/yellow/blue becoming brown/black/grey respectively for 3-phase.

Never mind - no point beating yourself up over that.

 

[EFLImpudence]

Not at all. I said that I do not see the logic in saying that it's "silly" to use black for the neutral just because of red/yellow/blue becoming brown/black/grey respectively for 3-phase.

That's what I thought you originally thought

What about using the cable as a drop to a 2-way switch, or a 2-gang 1-way with feed and two switched returns? Either way you end up with live - live - earth - live.

No choice then - but if there is a choice it could be argued...

 

[PBC_1966]

No choice then - but if there is a choice it could be argued...

I suppose, but I can't get worked up about it either way, any more than I can about which way round black & grey are sleeved!

With 3-core plus ground cable here which is spiraled into an overall round shape rather than being flat in-line, it's not something to even consider.