Boat wiring - polarity?

[Forty_Two]

I'm a bit puzzled as to why the instrument wouldn't work when wired up correctly - would there be a diode or something in there?

Yes, to protect against just such a situation. If not you would have caused damage to the kit.

 

[Stu Jackson]

Oh!

If you'd said originally that it was black and white, not black and red, then I'd straight away have said that it was to the US colour code. Their ABYC rules have a fairly detailed set of wire colours (for signal wires as well as power) and 12v power is black and white as Gordon says.

Pete

Pete, that's simply NOT true. US color coding for D.C. wiring is RED for + and black or now yellow for -.

For 120V A.C. wiring, black is +, white is neutral and green is ground.

 

[prv]

Pete, that's simply NOT true. US color coding for D.C. wiring is RED for + and black or now yellow for -.

For 120V A.C. wiring, black is +, white is neutral and green is ground.

Ah, fair enough. I must have mixed up DC and AC. It's never had any relevance to me so not something I'd try hard to remember.

Black = negative or neutral is pretty strongly baked into people this side of the pond, so your house wiring always seems weird to us

Pete

 

[VicMallows]

Black = negative or neutral is pretty strongly baked into people this side of the pond

That was too simple ... people could understand it. So we (or rather the EU) invented BROWN and BLUE. Allegedly so as not to discriminate against colour blind electricians. So all of us now often need to use a torch to tell the difference in poor light.

The colour code I can never remember is that used on the DC cable from most power cubes.....Is the black wire with the white stripe the neg or the pos

Vic

 

[Interlude]

Just to complicate matters my Hanse has Blue and Black for (different) negative/engine frame/"ground" wires, Black, Black with Red sleeve, White and Grey and Brown for various (different) positive wires. Is this the German method??

 

[Bilgediver]

Is that right? I know there's no 'ground' for things to short to, but what would be the rationale behind putting the breaker on the -ve ?

Have to ask Westerly as they did it for many years!

 

[KellysEye]

If you think reversal is confusing we've got the original European (Dutch) colour wires, the UK colours and the USA colours because equipment was fitted in each of those countries.

 

[VicMallows]

but what would be the rationale behind putting the breaker on the -ve ?

Probably the same as the often recommended disconnection of the negative battery terminal when working on a car .... though only really relevant if the battery in in the same compartment as the engine. The thinking is that a tool might accidentally short the battery positive terminal - even if disconnected - to exposed metal work. If the negative is disconnected it won't matter. Of course nothing will protect you if you short the two battery terminals

(if it's an ancient car/boat with 'positive earth' reverse all polarities).

Personally, I still prefer my isolator in the positive feed. Simply seems more logical and less likely to cause confusion in the future.

Vic

 

[nigelmercier]

Check out you switch/fuse panel there should be a bus bar that is -ve do you have a large conductor coming from the battery to that? What colour and what polarity is it?

I doubt that would help, it will probably be black whatever the polarity; that thick cable is too expensive to stock in both colours. I've put red heatshrink on all of mine.

Easy way to remember the UK mains colours, as told to me by a trainee about to wire up a plug: "earth is brown, live and blue have four letters, yellow and neutral have six..."