How to find out which wire is positive

[nigelmercier]

The positive wire is brown and the negative blue, green and yellow is earth. If it is old wiring red will be positive and black negative.

One assumes this is a joke.

 

[AMCD300]

One assumes this is a joke.

No, he's right...

 

[macd]

Now there are two jokers. True, I once bought a boat from a sparks and much of the wiring was brown-blue-green/yellow. But it's a big stretch to extrapolate from that that the OP's wiring is similar.

 

[David2452]

No, he's right...

Not really, low voltage AC can have a black or brown active conductor, neutral conductors can be blue or white and both may have a coloured stripe to aid identification, PE conductor can be green or green with a yellow stripe. As for the extra low voltage DC, that can be a rainbow of colours all of which are valid. That's even making the assumption it has been done properly, if not, which is more likely it could be speaker cable or bell wire for all we know

 

[AMCD300]

Not really, low voltage AC can have a black or brown active conductor, neutral conductors can be blue or white and both may have a coloured stripe to aid identification, PE conductor can be green or green with a yellow stripe. As for the extra low voltage DC, that can be a rainbow of colours all of which are valid. That's even making the assumption it has been done properly, if not, which is more likely it could be speaker cable or bell wire for all we know

You are right also.

The agreed point therefore is that you really can't tell unless you use a meter.

Yes, a potato is a novel idea (another new idea for me, Vic...) but if someone is seriously considering re-wiring their yacht then why on earth (excuse the pun) would you not go out and buy a small multimeter?

OP needs to test the polarity of terminals before dismantling the existing setup (I presume). This is a sensible approach, i.e. to make a good wiring plan of an old installation.

I love money-saving ideas and 'old sweat' tips, but cringe at Heath Robinson approaches when personal safety is a factor.

Buy a multimeter. Who cares what colour the wires are then...test and be safe.

BBROYGBVGWGS

Bon courage...

Andy

 

[planteater]

Place the bare wires in a beaker of water. The wire generating lots of (Hydrogen) bubbles is negative and the other one is positive.

 

[MASH]

The positive wire is brown and the negative blue, green and yellow is earth. If it is old wiring red will be positive and black negative.

It's a bit of a worry when people make posts like this as you can't tell if they are having a bit of a joke or are serious, and might actually try plugging the blue and brown into a potato (or, worse, might encourage someone else to).
To electrical tyros, if you see these colour combinations leave well alone
, they are likely 240v mains and can easily cook potatoes.

 

[Spyro]

All very funny and helpful but in all seriousness how do you learn about electrickery? I would dearly love to understand it but book learning tends not to be that helpful. My friend the Moomin just has to look at something and it is repaired or in a serious case pass his hand over the problem. How do you learn that trick?

Simple analogy.... batteries are a big tank of water (charge). Positive side is an outlet and the negative is the drain where all the water (charge) will run away. Connect a pipe from the outlet to the drain and all the water runs down it, this is you loosing the charge. You put devices in between the positive and the negative which are driven by the flow, the resistance of the devices slows down the rate of flow (discharge). think of it like narrowing a pipe or turning off a tap. If you have no flow of water i.e. all devices are turned off (taps closed) then no water flows (charge remains).
Any better???

 

[ip485]

have a cheap Fleabay LED on the end of two wires, it will only light positive to positive, negative to negative.

 

[AMCD300]

All very funny and helpful but in all seriousness how do you learn about electrickery? I would dearly love to understand it but book learning tends not to be that helpful. My friend the Moomin just has to look at something and it is repaired or in a serious case pass his hand over the problem. How do you learn that trick?

Something like this may help...

http://www.amazon.co.uk/12-Volt-Bible-Boats/dp/0713667036/ref=sr_1_1?s=books&ie=UTF8&qid=1313272021&sr=1-1

Not got a copy myself but others rate it highly for giving you the basics before moving on to more practical things.

Andy

 

[Evadne]

A trick is what it is.
...... The people who do that are the ones who think they know it, but don't. A little humility is the DIY equivalent of a condom on a one night stand - it protects against expensive and/or unhealthy consequences.

Slight drift, but IIRC there are four recognised stages of becoming skilled:

unconcious incompetence... you don't know how bad you are
concious incompetence ... You know what you should be doing, but know that you are biffo
conscious competence .... you can do it if you concentrate hard enough
unconscious competence ... you can do it with your eyes closed.

The dangerous ones think they are at stage 4 but are actually at stage 1 ....

 

[davidej]

Slight drift, but IIRC there are four recognised stages of becoming skilled:

unconcious incompetence... you don't know how bad you are
concious incompetence ... You know what you should be doing, but know that you are biffo
conscious competence .... you can do it if you concentrate hard enough
unconscious competence ... you can do it with your eyes closed.

The dangerous ones think they are at stage 4 but are actually at stage 1 ....

Sound a bit like Donald Rumsfeld.... "known unknowns etc etc"

 

[alan_d]

Sound a bit like Donald Rumsfeld.... "known unknowns etc etc"

Although I disagree with almost everything that Donald Rumsfelt has said and done, the knowns/unknowns quote, for which he was widely sneered at, is entirely sensible (if perhaps misleading in the context he used it).

 

[elton]

have a cheap Fleabay LED on the end of two wires, it will only light positive to positive, negative to negative.

Or it will burn your fingers off in a bright blue flash if it doesn't incorporate a series resistor.

 

[DaveS]

Although I disagree with almost everything that Donald Rumsfelt has said and done, the knowns/unknowns quote, for which he was widely sneered at, is entirely sensible (if perhaps misleading in the context he used it).

+1

 

[prv]

It's a bit of a worry when people make posts like this as you can't tell if they are having a bit of a joke or are serious, and might actually try plugging the blue and brown into a potato (or, worse, might encourage someone else to).
To electrical tyros, if you see these colour combinations leave well alone
, they are likely 240v mains and can easily cook potatoes.

Well, they may be, or they may not be. I've been on quite a few boats with 12v wiring done in mains flex. It seems to be especially common for lights at the top of masts (where of course the added corrosion potential means that this untinned cable is particularly unsuitable...)

Pete

 

[duncanmack]

Simple analogy.... batteries are a big tank of water (charge). Positive side is an outlet and the negative is the drain where all the water (charge) will run away. Connect a pipe from the outlet to the drain and all the water runs down it, this is you loosing the charge. You put devices in between the positive and the negative which are driven by the flow, the resistance of the devices slows down the rate of flow (discharge). think of it like narrowing a pipe or turning off a tap. If you have no flow of water i.e. all devices are turned off (taps closed) then no water flows (charge remains).
Any better???

Good analogy for current flow. Bad analogy for electron flow.
Ye pays yer money......