Mains Smoke Alarm

[Taylortwocities]

Grey is not a recognised colour to denote neutral.

As we often say on here, grey is just a colour, it doesn't know what it does.
And it should be over-sleeved blue, if it is a neutral.

When the 'harmonised' colours were introduced, the IET tried very hard to introduce a convention for cable colours (old v new colours) to steer installers away from using black as neutral (usually found in 3core + earth cables etc).

This convention is still detailed in Appendix 7 of the Regs - unfortunately it is only informative (guidance).

 

[Iggifer]

Answer this:
A customer removes an extractor fan, cannot fit the new one, calls you.
You arrive,

A) find hole in wall with red/yellow/blue wires with no sleeving.
(Did anyone ever sleeve the blue with black?)
Do you connect red to L, yellow to SL and blue to N without checking?
If not, why not? After all, Live is red, Neutral is blue and SL must be yellow.

B) find hole in wall with brown/black/grey wires with no sleeving.
What's the difference?

No difference whatsoever, and I always check regardless, but I find that, GENERALLY, grey gets used at Neutral. RYB is much more random in my experience. I'm not old enough to have installed it, so I don't know if there was guidance relating to those colours.

 

[sparkwright]

Using a harmonised black as a neutral when a grey is available causes UNNECESSARY confusion/inconsistency, whichever you prefer to call it.

There is adequate info to suggest grey is the prefered colour to use as a neutral.

Unfortunately this 'info' doesn't seem compulsory enough, so this is why people do things differently.

Also, there were too many short sighted people who thought 'neutral was always black, so I shall use this new black as a neutral'.

They need to remember that old colours aren't particularly meant to match up with any of the harmonised colours. They are two different sets of wiring colours.

 

[EFLImpudence]

Iggifer's reply would seem to substantiate what I am saying.

Using a harmonised black as a neutral when a grey is available causes UNNECESSARY confusion/inconsistency, whichever you prefer to call it.

...but you still have to check, so...

There is adequate info to suggest grey is the prefered colour to use as a neutral.

Adequate ? Where is this?
I can see nothing in Appendix 7 as referred above or the rest of BYB.
Please don't quote OSG, NICEIC or ESC or other 'guidance'.

Unfortunately this 'info' doesn't seem compulsory enough,

Is there a reason for that?

so this is why people do things differently.

Plus the fact that it doesn't matter.

Also, there were too many short sighted people who thought 'neutral was always black, so I shall use this new black as a neutral'.

As long as sleeved blue, it's compliant.

They need to remember that old colours aren't particularly meant to match up with any of the harmonised colours. They are two different sets of wiring colours.

Illogical to my mind.
A bit like wiring a two-way switch and not using brown as the permanent live strapper.

 

[Taylortwocities]

…..

 

[PBC_1966]

No difference whatsoever, and I always check regardless, but I find that, GENERALLY, grey gets used at Neutral. RYB is much more random in my experience. I'm not old enough to have installed it, so I don't know if there was guidance relating to those colours.

I'd say that where needing a permanent live, switched live for whatever purpose, and neutral with red/yellow/blue by far the majority of people used red for permament live, yellow for switched, and blue for neutral, with or without appropriate sleeving on the yellow and blue (more often without). That was so common that anything not done that way pretty much jumped out as being unusual. Why blue for the neutral? My guess is because of the existing association. Back in the 13th edition of the IEE WIring Regs. it was outlined that when using 3-core flexible cable (at that time with red/white/blue conductors) in a live/neutral/earth application the blue should be used for neutral (with the white sleeved green for earth). There wasn't even a requirement to sleeve the blue with black. Then from 1970-ish onward there was the added association due to the new brown/blue on flex.

With brown/black/grey I found much more variation for the reasons already discussed - The recommendations from some quarters to use grey (sleeved blue) for neutral to try and disassociate black with neutral completely versus the natural tendency to keep using the black even if now sleeved blue.

The bottom line though is that it doesn't matter so long as each conductor is appropriately identified. And that this debate wouldn't even be taking place if the powers-that-be hadn't decided to mess around with the perfectly satisfactory red/yellow/blue/black system for no good reason.

 

[eveares]

Here goes.......

Well, that refers to the identification markers, not the conductor insulation.

But if someone splices a 3 core + cpc cable in the middle where there would be no sleeving and a neutral is known to be one of the cores, at least they would know that grey would most likely be the neutral. Thus when no sleeving/tape is present, the core colour becomes the identification marker; Thus why the standard of using grey and not brown or black for the neutral exists.

Non-harmonized colours did/does use black for neutral and there is plenty left. Do you sleeve these brown and blue?

If you want to, but a new cable colour caution label would be better suited IMO.

Not quite - always sleeve neutral with blue.

Have yet to see the blue wire for a radial/RFC socket circuit sleeved blue. Sleeving a blue core with blue sleeving seems a bit ambiguous, what is the blue sleeving meant to indicate what the blue core does not already?

I don't get confused

You may not, but others may and thus is good practice to keep the old and new neutral colours septate.

The same can be said for the grey.

And that is why there is the standard of using grey sleeved blue for neutral in 3 core + cpc when a neutral is required and sleeving it brown when used for L2 in 2 way lighting circuits.

A) find hole in wall with red/yellow/blue wires with no sleeving.
(Did anyone ever sleeve the blue with black?)

One should sleeve the blue core with black sleeving to indicate neutral as blue is not a neutral colour in the old non harmonized colour scheme. Whether someone does is a different story.

Do you connect red to L, yellow to SL and blue to N without checking?
If not, why not? After all, Live is red, Neutral is blue and SL must be yellow.

Of course you would check, but you would hope that the Red core has been used for permanent line, Yellow core sleeved Red has been used for switched line, and Blue core sleeved Black has been used for neutral.

B) find hole in wall with brown/black/grey wires with no sleeving.
What's the difference?

One has the new harmonized colours, the other does not. Unless the fan you are wiring is 3 phase, you sleeve the cores their respective single phase colours.

New Black/Old Yellow and New Gray/Old Blue are 3 phase colours, not single phase colours - thus why you sleeve them appropriately. For not using Black or Brown for neutral, see top of this post.


Regards: Elliott

 

[Iggifer]

But if someone splices a 3 core + cpc cable in the middle where there would be no sleeving and a neutral is known to be one of the cores, at least they would know that grey would most likely be the neutral

Ridiculous statement. What if the 3C+E said person has spliced into is a two way strapper and therefore all live?! No neutrals present there, so regardless of if grey was ALWAYS neutral, it wouldn't apply in this scenario, so.....

 

[eveares]

Ridiculous statement. What if the 3C+E said person has spliced into is a two way strapper and therefore all live?! No neutrals present there, so regardless of if grey was ALWAYS neutral, it wouldn't apply in this scenario, so.....

Read the bold bit below....

But if someone splices a 3 core + cpc cable in the middle where there would be no sleeving and a neutral is known to be one of the cores, at least they would know that grey would most likely be the neutral.

 

[ban-all-sheds]

Why do you not power the alarms from an existing lighting circuit?

560.7.1?

 

[ban-all-sheds]

Read the bold bit below....

But if someone splices a 3 core + cpc cable in the middle where there would be no sleeving and a neutral is known to be one of the cores, at least they would know that grey would most likely be the neutral.

Let me see if I've got this straight:

You're positing a scenario where someone is cutting into a cable without having found either end of it, and therefore without knowing whether there is a neutral present, and without having been able to test for dead?

 

[sparkwright]

Right, back to basics.

First of all, in an old colour 3 core+E, with red, yellow, blue, how LIKELY would it be that the blue would be used for neutral?

 

[ban-all-sheds]

That depends very much on where it is.

 

[sparkwright]

OK.

On an interlinked smoke detector. Or a timed bathroom fan.

 

[ban-all-sheds]

OK.

Highly likely, IMO.