Cabling

[andyball]

Nearly all the re/blue/yellow insulated terminals are tinned copper anyhow, as are many uninsulated ring terminals...avoid plain brass if poss.,esp. on +ve feeds

www.beal.org.uk cheap for terminals/tools/untinned wire (with a bit of glue-filled heatshrink sleeve on each end, the plain copper cables take a v.long time to oxidise,since the air can't get in.....but if you buying from scratch-get the tinned stuff if price is ok.)

AMP terminals are the best (imo) but several times the price of the cheap stuff.

For joints to be unplugged occasionally-but prone to splashing-vehicle wiring products sell 4mm tinned bullets/receptacles ("japanese style") with "splashproof" rubber covers, much cheaper than "waterproof connectors" & v.adequate on motorbikes. But they need another type of crimp tool (beals again) & work best with 2.5sq mm + cable (smaller wires don't "seal" well at the cable entry. wurth uk also sell similar,but not tinned.-just noticed that ancor sell 'em too-p.47 of my catalogue.

 

[kds]

I recall advice from somewhere - use caravan connecting wire - 7 wires in a tough outer - weather resistant and easy to take more than enough wires everywhere, to attach to later, when you find at a later stage that you need another supply. If you need a higher current rating, just use two wires, it will carry 4 times the current for the same heating effect.

Check out some pictures of my boat at;
[link]www.canongrange.co.uk/boat/[link]

 

[Paulka]

2 wires, 4 times the current ?

Quickly apply for a patent, you'll be millionaire ;-)

Sorry, it's rather the contrary, it's not advisable to have two wires, or cables in // , as one of them will inevitably take more current than the other, thus get hotter, and take even more current, and get even hotter, etc. etc., untill smoke starts to show up.

You may double the wire's diameter, and then, you're right, the wire will accept 4 times the current.

 

[bedouin]

There's nothing theoretically wrong with connecting two cables in parallel - in fact there is a type of wire construction (called Litz) which uses several separately insulated conductors.

In a marine application, no wire should carry enough current to cause it's temperature to be increased significantly (apart from the starter motor) - if it is then you're losing too many volts. And even if it did increase the temperature, that would increase the resistance and so tend to reduce the current in the wire, rather than the other way round

 

[Paulka]

Hmmm.
No and yes.

You are right, and I am wrong on the temperature coefficient, which tends to limit the current when the temperature rises.

You are right, there is nothing wrong to have one or more wires or cables connected in parrallel, as long as each individual wire or cable is protected by its own fuse or cb.

The reason for this : if one of several wires is interrupted (broken, disconnected, etc.) the other(s) will take over the load, and may be overloaded, leading to overtemperature. If all wires are protected by one "collective" fuse or cb only, then this "collective" fuse or cb will not "see" any overload although the remaining healthy wires are overloaded indeed.

In short, protect each individual wire with its own fuse or cb.

 

[Strathglass]

Two wires are fine. As long as. They are EXACTLY the same length and EXACTLY the same wire type. This way, they will be exactly the same resistance and be able to dissipate exactly the same power. Then you can double the current with the same voltage loss as a single wire, as long as the heat generated can be dissipated.
If however you use a multicore cable with several wires of different diameters and connect two different diameter wires in parallel. The rating of those pair of wires is determined by the rating of the thinner wire of the pair and will probably not be as high as twice the current carying capacity of the thinner wire because of temperature increases.
If parallel wires are identical in length and characteristics then several wires can be connected together and , in these circumstances, each wire does not require to be individually fused.

Iain


<P ID="edit"><FONT SIZE=-1>Edited by iainsimpson on 07/12/2002 20:19 (server time).</FONT></P>