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The hard and fast rules of coloured wires

Hi all,
Now, it may be some 15 years ago, but I was always taught at school that
basic wiring went thus, Positive was red and Negative was black ???
Simple I know till we hit the realms of DCC, but I'm not on about that
today.. (Or Hornby where they adopted the Henry Ford livery, any colour, so
long as it is black!)
Well, it seems that Express models have also started going away from the
norm ! Imagine my utter astonishment when I took home some of the very nice
yard lamps that they retail, go to read the destructions, just to make sure
and I find two wires from the LED and a resistor.....
OK, so I have a white and a black....
Connect resistor to black... OK....
Now connect Black to your + feed and white to the - ...... Eh ??
It was bad enough wiring the DCC lighting kit into the class 37 when the
instructions had a blue, yellow and white wire to match your leads on the
chip, but the LED's your sent to fit had only Red and Black as colours !
Come on, lets get the simple bits right, then we can finally progress....
Reply to
Andy Sollis CVMRD
Loading thread data ...
But that changed to Brown for + and Blue for - in the uk a long time ago in some cases
Reply to
Trev
"Andy Sollis CVMRD" wrote in message news:eo5kbm$hko$ snipped-for-privacy@aioe.org...
Well white is the return (-) side of the LEDs in computers and I suspect other electronic units.
Reply to
Jerry
"> But that changed to Brown for + and Blue for - in the uk a long time ago in
No it has not!!!! The change to brown and blue was for MAINS AC wiring, which has no +ve and -ve.
Jeff
Reply to
Jeff
Hi Andy,
For DC there are no hard and fast rules. The usual convention is
+ positive from ground = red
zero volts (ground) = black or white or green
- negative from ground = blue
But it's entirely up to you. Normally the "warmer" of the two colours will be positive with respect to the "cooler" of the two colours.
For mains AC, the legal convention is brown for line and blue for neutral (AC doesn't have plus and minus). Low voltage AC is usually both white or both black.
For electronic components such as LEDs, etc, the usual convention is that the longer lead is positive. You can remember that by mentally forming a plus and minus symbol out of the leads (+ symbol needs extra length for the cross arm).
regards,
Martin.
Reply to
Martin Wynne
On 11/01/2007 15:15, Andy Sollis CVMRD said,
AFAIK there has never been any hard and fast convention. How positive is positive? At work, for instance, we tend to use black for 0V, but red, violet or yellow for various positive voltages. Blue is used for negative voltages, or white, or orange. Then another customer may have a totally different wiring convention - one uses your Henry Ford analogy, but as all wires are idented anyway the colour is actually irrelevant.
I've long since found that what I was taught at school doesn't reflect the real world :-)
Actually, there is a convention I've just thought of. When you're disarming a bomb, you *always* cut the blue wire :-)
Reply to
Paul Boyd
I think it used to be red for live and black for neutral in some cables (solid core rather than flex) but I'm pretty sure that's changed to brown and blue now as well. Something to do with harmonising with other countries' colours.
peter
(After just getting my head around 3 phase supplies, the sparky on a site where I was working had to keep looking up the new cable colours as the generators used the new colouring system but the equipment being connected used the old colours!)
Reply to
naked_draughtsman
On 11/01/2007 21:43, naked_draughtsman said,
Ah, but this is all to make mains wiring much easier and less confusing!
The nice bright colours used for three-phase are now being replaced by dull colours that will be hard to distinguish in dirty, dark and dusty electrical boxes, black was neutral and is now one of the lives, and blue was one of the lives and is now neutral. Still, I guess the EU must know what they're doing, mustn't they? I'm sure there won't be any scope for dangerous errors and confusion, will there?
Reply to
Paul Boyd
If you allow people to work in other parts of the EU, confusion will arise unless the colours are standard throughout. Inevitably some countries have to change their traditional colours.
Mark Thornton
Reply to
Mark Thornton
I recently replaced a bathroom extractor fan and was introduced to the delights of twin-live four wire connections for the first time. The box which Screwfix sent me included an invitation to join "The Guild of Master Craftsmen" which gives you some idea of the entry standards required by that particular organisation. I've never replaced an extractor fan before in my life.
(kim)
Reply to
kim
I think the entry standerds are paying the fee
Reply to
Trev
The message from "kim" contains these words:
Did you inform the Local Authority's building regs department that you were intending to do electrical work in the bathroom? When the new mains cable colours came in the regulations were changed: Kitchen, bathroom and outdoor electrical work is for qualified professional electricians only and they must supply a certificate to show the work is up to standard...
I thought it was a joke, but it's all too true. The amount of DIY electrical work officially permitted now is very limited.
Reply to
David Jackson
I think there may also be something in the choices of colours to help the colourblind.
Reply to
Paul Matthews
The IEE have always been the odd men out in the mondial electrical convention. It was showing up 30 years ago when German kitchen equipment and Danish Industrial kit were using Green as a line conductor. Europe decided that such conventions as Line & Neutral plus Earth were pointless and accident prone and so why not make the two line wires interchangable? Earth connections reserved for loads of > 6 Amps. Most European Countries have not allowed themselves to be subjugated to " Authorised" "technicians" -- such as Corgi!!! We were all offered these credentials for a simple cash exchange. It was a very cynical move on the part of the gas monopoly of the day. The IEE changed their rules (how did they get in charge) so often that most electrical contractors were for ever buying new editions (of the regs) . Manufacturers could not keep up with the cable size changes and the ridiculous situation arose where wiremen had to remove some conductors from multistrand cables in order to fit them to the terminals provided in the power boxes. I can travel to any EC ( and other Euro country) and use the same power plugs but the UK is different.
Reply to
Peter Abraham
David Jackson said the following on 11/01/2007 22:58:
You're right - it is true. The catch is that unless you're connected to the trade in some way, you won't know about it! The likes of B&Q will still happily sell you an extractor fan, but they will "forget" to tell you that you're no longer allowed to install it yourself. Apparently we're not even allowed to wire in a cooker any more!
Just to give you an idea of how daft the rule can be, at work we produce electrical and electronic widgets. Some of these are 3-phase control boxes. To test them, we plug them in, and poke about with live 3-phase around. We don't need special qualifications to do this. However, we need to move a 3-phase connection box which is part of the building wiring, but because we don't have the right bit of paper we are not allowed to do that and have to call in an electrician to do this job!
It's getting to the point where we won't be allowed to change light bulbs any more!
Reply to
Paul Boyd
Not had much experience at defusing bombs but, when I were a lad in the early 50's, the company I worked for sold some Italian vacuum cleaners which had metal cases. The earth connection was red ! I think the live was beige. There was no standard mains plug at the time, the customer had to fit their own, very often a bayonet in the light socket. We managed to cull quite a large proportion of the local population with those things. We also had 3 mains voltages in our immediate vicinity. 110, 210 and 230.
Reply to
Brillo
And then only for flex.
Fixed wiring (ie the stuff buried in the walls) has only recently changed to the new European harmonised colours.
MBQ
Reply to
manatbandq
And even more confusion when the "foreign" sparky comes to the UK and finds there are now two standards, the old and the new, which, as has been pointed out wrt 3-phase, can be dangerously confusing.
MBQ
Reply to
manatbandq
That is simply not true, anyone can still do the work. It is still perfectly legal to DIY in any situation.
Suitably qualified people can self-certify their own work and issue the paperwork.
If you DIY then you shouold inform your local councils building control officer who will arrange for an inspection. There will be a fee for a building notice but they are not allowed to charge extra for the actual inspection.
MBQ
Reply to
manatbandq
There has been no change to what is permitted as DIY work. Only the inspection and certification regime has changed.
Yes you are if you first submit a building notice to the local authority. What you will not get away with is doing a shoddy job.
MBQ
Reply to
manatbandq

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