by ericmark »
Sun Nov 02, 2008 8:49 pm
On a single phase system all line wires should be brown and all neutral wires should be blue. Older systems would have been Red and Black. However cables with two reds or two browns are both more expensive than the brown and blue and hard to follow the same with three cores three reds or three Browns are harder to follow and more expensive than red, yellow, blue or new colours brown black and grey. As a result it is the norm to used wrong colours and fit sleeves to show they are line rather than neutral cables.
Although this is allowed because they all should be one colour either red or brown according to age of installation there are no fixed colour codes for the base colours only for the sleeves put on the wires which will be all red or brown.
Having said that at the rose normally all base colour red or brown go together on to central loop terminals the one sleeved wire goes to double connector block and the rest of black or blue go to three way connector block.
At the switch there are only two wires except with two way switching and both switches in pair have same colours to each terminal.
There are some diagrams on my site
http://www.ericpalmer.fsnet.co.uk/Lighting.html which may help.
In industry we would use numbered cables and have plans showing what each cable does (Well we should have) but making "as built" plans cost time and money and if a house was built that way it would cost double what it costs now to wire up.
Green/Yellow is always earth sometimes sleeves fall off and they are bare wires.
The grey wire is normally only used between switches and not on ceiling rose with exception of bathroom where three core is sometimes used to feed fan.
Eric
