Connect 3 Core and Earth Cable to extractor with LNT

[lesliemk]

My old extractor fan is giving issues and I got a new one. It has the usual 3 marked ports for L, N and T. But the old wiring uses the 3 core and earth cable, which has a black, brown, grey and yellow/green wires. Does anyone know how to wire it properly? Thanks

 

[bernardgreen]

If the old fan is still connected then you should be able to determine which wire is which by the labels on the terminals they are connected to on the old fan.

 

[lesliemk]

Thanks @bernardgreen On the old one, brown goes into L, black in N and grey goes to one marked I. Attached is the picture. I am struggling to understand what I stands for.

 

[ericmark]

It is common to use cable with cores of red, yellow, blue, or brown, black, grey, but really they should be red, red, black, or brown, brown, blue, so in general the wire colours mean nothing. May be lucky and some one has used red or brown sleeving but in the main it is look how old one is wired.

On the old one, brown goes into L, black in N and grey goes to one marked I. Attached is the picture. I am struggling to understand what I stands for.

So if you make sure black goes to N, if other two wrong way around unlikely any harm done.
Seems likely Brown again will go to L.
So grey to T instead of I.

 

[bernardgreen]

I agree with Eric

 

[JohnW2]

I agree with Eric

Same here.

Kind Regards, John

 

[winston1]

It is common to use cable with cores of red, yellow, blue, or brown, black, grey, but really they should be red, red, black, or brown, brown, blue, so in general the wire colours mean nothing.

That would be really silly. How could one tell which red (brown) was which?

 

[Risteard]

That would be really silly. How could one tell which red (brown) was which?

It's not silly. It's a requirement.

A single phase phase conductor must be coloured brown (and previously red).

 

[JohnW2]

It's not silly. It's a requirement. A single phase phase conductor must be coloured brown (and previously red).

In the UK (per BS7671), a single phase conductor must be identified as such at its terminations, one acceptable method of such identification being by having brown (previously red) insulation or sleeving at its terminations.

 

[plugwash]

AIUI In the days when flex was harmonised but fixed wiring cables were not, the norm when using a 3 core cable in single phase with neutral applications was to use red as (permanent) live, blue as neutral and then yellow would be used for whatever was left over (e.g. earth on a 3 core SWA, or switched live on a fan).

Unfortunately when the harmonised colours were revised to have distinct colours for all three phases and UK fixed wiring moved over to harmonised colours, grey was chosen to be the L3 colour and black the L2 colour. Industry organisations pushed for a direct application-agnostic replacement of old with new which ended up with grey as neutral and black as the extra.

Meanwhile a DIYer is more likely to pick black as the neutral and grey as the extra.

So nowadays you really have to look at the existing.

 

[JohnW2]

... Industry organisations pushed for a direct application-agnostic replacement of old with new which ended up with grey as neutral and black as the extra. .... Meanwhile a DIYer is more likely to pick black as the neutral and grey as the extra.

Maybe (in both cases) but the actual insulation colour is not really all that relevant, is it, since the conductors have to be identified as to what they are being used for, usually with over-sleeving at the terminations. It therefore does not really matter whether grey or black is used as neutral, since either should have blue over-sleeving - and the 'extra' (of whatever colour insulation) would have to be over-sleeved with brown or G/Y (or, I suppose, blue, if there were two neutrals!!).

Kind Regards, John

 

[ericmark]

AIUI In the days when flex was harmonised but fixed wiring cables were not, the norm when using a 3 core cable in single phase with neutral applications was to use red as (permanent) live, blue as neutral and then yellow would be used for whatever was left over (e.g. earth on a 3 core SWA, or switched live on a fan).

Unfortunately when the harmonised colours were revised to have distinct colours for all three phases and UK fixed wiring moved over to harmonised colours, grey was chosen to be the L3 colour and black the L2 colour. Industry organisations pushed for a direct application-agnostic replacement of old with new which ended up with grey as neutral and black as the extra.

Meanwhile a DIYer is more likely to pick black as the neutral and grey as the extra.

So nowadays you really have to look at the existing.

Yes before harmonised we had brown and two blacks over the channel which was a real pain, grey only started to be used after harmonised, the problem is blue was a phase colour and now black is a phase colour so getting neutral right is a little bit of a problem, OK I know neutral is live, but could have done with black and blue not being one of the new colours.

 

[plugwash]

Maybe (in both cases) but the actual insulation colour is not really all that relevant, is it, since the conductors have to be identified as to what they are being used for, usually with over-sleeving at the terminations. It therefore does not really matter whether grey or black is used as neutral, since either should have blue over-sleeving - and the 'extra' (of whatever colour insulation) would have to be over-sleeved with brown or G/Y (or, I suppose, blue, if there were two neutrals!!).

Yes wires should be sleeved, whether or not that actually happens in practice is another matter.

 

[JohnW2]

Yes wires should be sleeved, whether or not that actually happens in practice is another matter.

Indeed so. But yet another 'another matter' is whether, in some situations, such 'identification' is actually necessary and/or serves any useful purpose - as, for example, with cables going to light switches.

Particularly in the case of 2-way switches, functional identification of conductors would be useful - but, of course, the requirements of the regs do not achieve that.

Kind Regards, John

 

[Risteard]

In the UK (per BS7671), a single phase conductor must be identified as such at its terminations, one acceptable method of such identification being by having brown (previously red) insulation or sleeving at its terminations.

You're hardly claiming that it has been heatshrinked with alphanumeric markings, are you?