Question on cable size

[rmgcsj]

Now coming to the end of a refit I need to wire up the nav lights. The Bi colour light has a 25w bulb in it. The boat is 7m long. Am I on the right lines when working out the volt drop to be approx 0.5A I can use a cable size of 1.5MM? The cable size was 2.5mm but seemed larger than needed. All wiring comments appreciated.

 

[Nigel_Ward]

This American Chandler's website gives the type of info you require
http://www.westmarine.com/pdf/0660_ETRIC_MC04.pdf

Hope it helps

 

[billcowan]

Simple; the thicker the cable, the less the loss. On long runs it is really important, So Masthead light make it 2.5

By the way always use multi strand flex and not the cheaper solid house wiring stuff. Big loudspeaker cable from a 'geek' shop is good. motor factors have it also, but not as twin.

Better connections can be ensured by 'tinning' the ends with solder where they go into screwed terminals. better still, solder every joint that you wont need to take apart.

 

[VicMallows]

You say a bi-colour, so I assume you mean on the pulpit rather than up the mast. In which case 1.5mm should be fine (I'd say it's fine if up the mast also).

There's even an argument that although the light output will be slightly reduced by voltage drop, so will the current consumption, and the bulb life will be extended. A 25w bulb on a 7m boat should be amply bright enough anyway, IMHO.

Vic

 

[boatmike]

Agreed.
There is never any harm in fitting oversized cables in any case. The money you save by fitting the bare minimum size is peanuts. Up the mast you should not only use 2.5mm minimum but it should ideally be waterproof rubber sheathed cable with tinned wire throughout. Contrary to popular belief PVC sheathed cable is not waterproof and will corrode over time.