Correct colour code for switched-live

rowanbradley · 30 Dec 2009

I'm wiring in a new outdoor photo-electric/time switch for my driveway light. The switch has three terminals, live, switched-live and neutral. Can anyone recommend the correct colour code for these three wires (and in particular for the switched-live wire)? The switch needs to have a single, round cable going to it, since it has to seal into a gland, and I need to buy a suitable cable.

If I can't get a suitable cable, is it allowed by the regulations to use a standard brown/blue/green-yellow cable and sleeve the ends to show the correct colours? Note that this will incolve sleeving the green-yellow cable to be something else - live or neutral.

If the above is not permitted, I guess the next alternative is to use 4-way cable, and just not use the earth wire (I can connect it to earth at the other end). If I do this, is it permissible to sleeve the other wires where they are not the correct colour?

Many thanks - Rowan

Taylortwocities · 30 Dec 2009

The earth must be used and connected to earth at teh source end, even if the device it is feeding does not have an earth connection (eg for a double insulated device).

This conductor is a very important safety feature and will be required when you test the Earth Fault Loop Impedance before the circuit goes into service.

So you'll need 3 core and earth cable. Or 4-core flex. But see edit below.

Usually:
Brown is permanent live
Grey, sleeved with blue = neutral
Black, sleeved with brown = switched live.

Edit:
1. If this cable is being run outside you will probably need steel wired armoured cable. you cannot and must not drape PVC flex around your garden.
2. Are you aware that this work is notifiable under building regs Part P.
Please check the WIKI for information.

conny · 30 Dec 2009

3 core +earth.

Brown- permanent live.
Blue - neutral,
yellow- switched live.
Earth - earth.

You cannot use the earth for anything other than earth under any circumstances

Damm again!

(TTC you a professional typist or summat?

)

Taylortwocities · 30 Dec 2009

Yup, Pitmans trained 350,000 words per minute.

By the way, where do you get cable with brown, blue and yellow conductors

ColJack · 30 Dec 2009

conny said:
3 core +earth.

Brown- permanent live.
Blue - neutral,
yellow- switched live.
Earth - earth.

You cannot use the earth for anything other than earth under any circumstances

Damm again!

(TTC you a professional typist or summat? )

you wanna try that answer again in one colour code or the other?

conny · 31 Dec 2009

Typing too quickly and got mixed up.
Please accept my apologies.

350,000 words per minute

Not as fast as I thought then.

ericmark · 31 Dec 2009

In a single phase installation are Line (Phase) wires should be Brown and all Neutral wires should be Blue if colour system is used. With green and yellow for earth.

It is common to use cable coloured with the three phase colours of Brown, Black, and Grey and to sleeve the cables with brown or blue to identify however since the cable is not designed for what it is used for there are no colour codes.

For DC installations Brown and Grey are Phase colours so to used the remaining colour as neutral would make sense plus in past black was used for neutral so industrial electricians will tend to used black as the neutral so that all systems are the same.

However on split phase systems blue is often used as L2 even though L2 should be black so there will never be agreement in what colour to use. So long as the green/yellow and Cream is always used as earth any other colour can be sleeved with colours or numbers.

To say either Grey or Black should be used as Neutral or Switched line without explaining that there is no convention is dangerous as people can make the mistake of thinking this is a convention and make mistakes as a result.

TicklyT · 31 Dec 2009

ericmark said:
...For DC installations Brown and Grey are Phase colours ....

Does DC have a 'phase'?

DC distribution in some industries is identified as Grey = positive, which is usually maintained at about earth potential, and Blue = Negative, the live conductor. That replaced an earlier convention where Black was the live and Red was earthed.

OP - Use whatever makes sense to you, Identify the conductors with blue or brown sleeving and make a note for future reference, or use by others. A note on the inside of a cover can save a lot of head scratching later on.
Just don't use the CPC / earth wire for anything other than earth.

joinerjohn · 31 Dec 2009

TTC says "The earth must be used and connected to earth at the source end, even if the device it is feeding does not have an earth connection (eg for a double insulated device). ".

With my limited understanding of electrics, the question goes begging. If the device being fed is double insulated and has no earth connection, How does the OP terminate the earth at the device?? Does he just cut it as short as possible?????
Might seem a daft question but surely you wouldn't want an earth wire that can't be terminated ?

sparkwright · 31 Dec 2009

you connect the earth wire to a piece of connector block, which you'll probably have to supply yourself.

Taylortwocities · 31 Dec 2009

joinerjohn said:
Might seem a daft question but surely you wouldn't want an earth wire that can't be terminated ?

The earth (cpc) is not there to make the device function but it is installed in order to provide a guaranteed earth return path for the circuit. It is there so that the cpd will disconnect quickly in the event of an earth fault at any point in the circuit (and that includes the cabling itself).

rowanbradley · 31 Dec 2009

ericmark said:
In a single phase installation are Line (Phase) wires should be Brown and all Neutral wires should be Blue if colour system is used. With green and yellow for earth.

And if I'm using this scheme, what colour should switched-live be? If I have to sleeve it, what colour should the sleeve be? I've seen yellow, brown, black and grey mentioned. It seems odd that such a common function as switched live should not have a standard colour. Sleeving it brown (which I've seen suggested) seems very unhelpful, and provides no way of distinguishing between the live feed to the switch, which should always be live, and the output from the switch, which will sometimes be live, and sometimes not (so voltage-wise it will be picking up neutral through the load). Using black seems a bad idea to someone who remembers the old cable with black for neutral.

Thanks - Rowan

mikhailfaradayski · 31 Dec 2009

the sleeve should be brown. you don't need to sleeve it 100% of its length, so you would still be able to see the colour of the insulation beneath and identification won't be a problem.

imagine the cost and manufacturing implications of having to supply cables with additional colours just to get rid of sleeves.

securespark · 31 Dec 2009

Sorry to hijack this!

Hi Rowan!

Just like to ask you a Q, if it's not rude: how old are you?

It's just that we have a son called Rowan and we only know three others:

Mr Atkinson.

Mr Williams.

and

Ms Pelling.

None share a generation!!

Thanks.

Normal service will be resumed as soon as possible.

Our Rowan is 5 btw!

EDIT:

Atkinson b 06/01/55

Williams b 14/06/50

and

Pelling b 17/01/68

Paul_C · 31 Dec 2009

rowanbradley said:
It seems odd that such a common function as switched live should not have a standard colour. Sleeving it brown (which I've seen suggested) seems very unhelpful

If you want to follow BS7671 to the letter, then all live conductors on a single-phase installation should be brown, either by the original color of the insulation of the wire or by sleeving. It's been this way for a very long time, i.e. under the "old" color code both live feed and switched live were supposed to be red.

As noted already, you can apply the sleeving but still be able to identify which wire is which from the underlying color.

To clarify the key points:

* Green/yellow conductors may be used only for a protective earth and should not be sleeved and used for any other purpose.

* Any other color conductor may be sleeved to match its intended use, including the application of green/yellow sleeving for use as an earth.

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Correct colour code for switched-live

joinerjohn

Paul_C

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