Originally Posted by richardjawilson
Hi there I'm wanting to rewire my nav lights and was thinking of using a twin core cable from the switch to the A frame.
Is 1.0mm 16 amp ok, too big , too small, or would 11amp 0.5 be fine??
I'm not really up to speed on cables.
Any help would be great.
Firstly, not sure where your current ratings come from, they seem a little over optimistic to me.
I do not know what current rating your nav lights are, mine are 10W, so I will take that in absence of anything better. Taking the worst case, that is you are wiring the red and green in series, you will be drawing the current for both lights. If both are 10W, voltage is 12V, and VI=W (V, voltage, I, current, W, wattage), I =20/12, or slightly less than 2amps. Sounds OK, but volt drop down the cable run is usually the major issue for our sort of applications. Assuming a 10 metre length (out and back) your volt drop will be something like 1V. So I would definately not go any smaller than 1mm cable. If you went to 2mm cable your volt drop will be of the order of 0.2V. From memory standard size widely available is 2.5 mm; I would try to find some of that.
Sorry to come over all chalk dust, I do a little bit of this in the day job. If I have been over pessimistic in any of these calculations, apologies, let me know.