Switched live colour

[zaax]

What colour is switched live? ie from switch to bulb or from thermostat to boiler

[nightjar]

A single light switch is normally wired using twin and earth cable, using the live to take the power to the switch and the neutral to take the switched live to the luminaire. Twin domestic light switches often use three core and earth, again using live to take power to the switch and the other two wires to take the separate switched lives. The switched live(s) should be sleeved at both ends in the same colour as the live. The colours of the wires and sleeves will depend on the type of cable used and the age of the wiring.

I've never wired a thermostat to a boiler, but I presume it would follow the same practice.

Colin Bignell

[Dave Plowman (News)]

The correct answer is to establish what has been used in your circumstances, as it is unwise to assume anything with electrics.

With a switch which uses a normal TW&E pair it would *usually* be the black or if new cable, blue. But you can get TW&E with two reds (or two browns) specifically for this purpose.

Where a Triple and Earth is used for a thermostat there are even more variations possible. With the old colours, I used :-

Red - feed. Blue - Neutral Yellow - Switched return.

But others will have a more logical sequence - to them.

[TheScullster]

"zaax" wrote

As others have said, this can vary, so the simple and safest answer has to be "the one that your tester confirms it to be". The older the house (sweeping generalisation coming up) the more likely that colour codes have been ignored.

Phil

[Andy Wade]

So far as BS 7671 (wiring regs) is concerned the correct colour is brown. If a differently coloured core in a multi-core cable is being used, it must be sleeved brown at all terminations.

Using 3-core & earth cable for a 'stat you should use:

- brown core: live/line/phase feed from boiler etc.

- black core, sleeved brown: switched live back to boiler

- grey core, sleeved blue: neutral

- bare core, sleeved green/yellow: CPC.

[Lobster]

And in fact, as I discovered earlier this week (qv!), if you buy 4-core heat-resistant flex to use within the confines of the boiler casing, you get brown, black, blue, grey and green/yellow, which matches up with the above cable colours, respectively.

David

[tinnews]

That makes five cores! :-)

[Lobster]

Doh! (just wondered how long it would take someone to notice)

Read: "brown, black, blue, green/yellow"

David

[Lurch]

On Fri, 04 May 2007 13:26:35 GMT, Lobster mused:

It's always been like that, brown blue and green\yeloow as normal 3 core flex with balcks added to make up the extra cores for 4 or 5 core flex.

[Lurch]

On 3 May 2007 00:11:38 -0700, zaax mused:

Bit vague. Not quite sure how anyone can answer this with any accuracy whatsoever.

[mike]

The sensible posters have made a good stab.

[Lurch]

On Sat, 05 May 2007 21:57:37 +0100, mike mused:

Yeah, ansd whilst they are all correct I'm not sure if any of them have answered the question or made matters worse and cOnfusEd tHE OP even more.

[mike]

Perhaps the OP has more common sense than you do.

[Lurch]

On Sat, 05 May 2007 22:37:13 +0100, mike mused:

Doubtful, looking at the question.

[Matt]

So that's why 6 core flex, off the shelf from just about any UK electrical wholesalers for the past quarter of a century or more, has brown, blue, green/yellow, black, white, red cores then?

...and 5 core is brown, blue, green/yellow, black, grey

and 7 core is brown, blue, green/yellow, black,white, red, grey

Extra black cores are typical of a continental approach where everything needs ferrules. Having said that, about 25 years ago RS once sold some 1mm^2 signal cable with one black core and 49 whites - all un-numbered but perfectly usable without buzzing them out - if you respected the cable lay.

[Lurch]

On Tue, 08 May 2007 21:45:02 +0100, Matt mused:

All of the hundreds of metres I've bought, in split lengths and on drums, from wholesalers up and down the country over the last 10\11 years have been brown, blue and green\yellow with black cores for the extras on 4 and 5 core. Anything more than 5 core has had all black cores with a green\yellow.

I'm not saying that no other cable colours are available, but IME the extra cores are all black. I don't actually care what the colours are.