Question on wiring size

[changeman]

Can anyone advise me how to determine the size of a wire. Is a 10 mm sq cable really just the area of its cross section, or is this just too obvious? Can I just use a vernier guage to measure diameter?
I know what size wire I need, just don't know if my existing wiring is big enough.

 

[snowleopard]

It's the area of cross-section of copper so you won't get a correct answer by measuring the diameter of the cable- that will give you a figure including the air spaces between the strands. You would need to measure the diameter of the strands, calculate the x-section of the strand then multiply by number of strands.

 

[boatmike]

Thats quite correct but if you are buying the stuff it is sold by cross sectional area anyway. If you already have some the easiest way to size it is to take a bit into a retailers where they sell the stuff and compare with what they have on the drum rather than measure it but make sure you are comparing the same size wire strands and numbers of wires as this will vary

 

[jrt]

The more strands you have in the cable, for the same overall size, the more flexible the cable. Because the boat itself is vibrating and flexing you should use flexible wiring. Domestic cable, with maybe only one conductor, is stiff. The stiffer the cable the sooner it will go brittle, the sooner it will break.

What you should be using is tinned copper conductors. As above, with lots of fine strands, but each one should be tinned. (Shiny silvery coloured, not copper coloured). It takes salt water a lot lot longer to rot tinned copper conductors than untinned conductors.

Tinned copper is more expensive, but not by much, and harder to find. It really depends on how good a job you want to do, how long you want it to last.

 

[Salty John]

Roughly, 6 gauge is 0.182" diameter, 8 is 0.137, 10 is 0.109, 12 is 0.086, 14 is 0.069 and 16 is 0.055. These figures are from Charlie Wing's Handbook of Wiring.

 

[Evadne]

Some useful tables here as well.

 

[boatmike]

Agree generally, especially regarding tinned wire. The finer you go on wire size though the more flexible the cable becomes but the more susceptible the cable is to corrosion especially if bare copper wire is used. There is a compromise here!

 

[penultimate]

I think the previous replies give you all you need to know; but, for what it's worth, the Maplins Catalogue gives a lot of useful data on cables, though of course most of their cables are not recommended for marine use.

 

[changeman]

Thanks all. I am now enlightened.