[Gllug] OT: Mains electricity colour coding.

[Gerd Busker]

Bernard Peek wrote:
> On 24/10/10 18:58, general_email at technicalbloke.com wrote:
>   
>> For time immemorial I have been told brown is live, blue is neutral and 
>> yellow/green is earth. Mains electricity is AC so it oscillates between 
>> the positive and negative 50 times a second right? In that case why does 
>> it matter which way you wire the blue and brown cables to the nominally 
>> blue and brown terminals in a plug? 
>>     
>
> Neutral is connected to ground at the substation, so only the live
> connection is dangerous - if everything is wired properly.
>
>   
In many countries brown/blue are completely interchangeable.  I think 
the UK is one of the few countries where a plug is phase/neutral 
specific, even though many countries indeed tie blue to ground somewhere 
along the line, certainly if it is actually 1 tap of a 3-phase system 
(which almost all power is).

If you look at a 220V shaver socket, there both pins are "floating" 
(with the help of a transformer).  If you grab one (don't do this at 
home) in theory you bring it to neutral and the other end is live so 
you're safe!

My house in holland had both blue and brown live at ~110V in opposing 
phase - I was never sure if this was by design or not.
Bascically you treat blue as live, since it often can be.

Gerd.


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