Size of cables for mast re-wire?

[Georgio]

Hi,
With the mast down I plan to replace the cables for the LED masthead light and the steaming light (25W) as the old cable is well corroded and I have an intermittent fault. But what size cable do I need?

I’m guessing the LED masthead light (NASA supernova) will be fine with the thinnest stuff 0.5 to 1mm. Mast length is circa 40’ if that helps

What size cable is needed for the 25W steaming light. 1.5mm or 2.5mm.

Please help???

 

[Jabs]

Hi,

Not sure why you wouldn't change all the lights to LED whilst you are at it??

You can use a LED Festoon in the original steaming light.

Also, might be a more reliable solution to use the old masthead light and convert to LED rather than risk a NASA LED light??

I would personally use 0.5mm wires for LEDs but find something physically strong so you don't worry if pulling them through is a task.


Good luck

Tony

 

[VicS]

Hi,
With the mast down I plan to replace the cables for the LED masthead light and the steaming light (25W) as the old cable is well corroded and I have an intermittent fault. But what size cable do I need?

I’m guessing the LED masthead light (NASA supernova) will be fine with the thinnest stuff 0.5 to 1mm. Mast length is circa 40’ if that helps

What size cable is needed for the 25W steaming light. 1.5mm or 2.5mm.

Please help???

Taking the total distance to the steaming light and back again as 20m you will need AWG 14 or 2.0mm² minimum to avoid a volts drop of more than 3%. Heavier if the total distance is more


The wiring to the LED light can be quite light because the Supanova will operate at full brightness down to 10volts and the current is only 200mA.
In theory 0.5mm² cable will be adequate ( assuming "there and back" distance of 30m) but I would not go any smaller than 1mm² or even perhaps 1.5mm² for robustness

 

[Enya]

How far in meters is it from your battery to your steaming light and back to the battery? 30 meters? The voltage drop for 2.5mmsq cable for this 2 amp bulb is 2X0.754 = about 1.5 volts per 100 meters. You should be looking at no more than a 3% loss on nav lights. ie 0.36 volts. So 30/100 x 1.5 = 0.45 so even 2.5 mm sq is too thin for a 30m run.

1mmsq cable has a resistance of 1.884 ohms/100m. The NASA LED is 1/5th amp. Voltage drop is 0.615 volts over 100m. Looking good if difference mast and back is less than 50m. Cant tell you what the resistance of 0.5mmsq cable is but may be borderline.

I am referring to the Marine Electrical and Electronics Bible by John Payne. Hopefully I have done the sums right. Surely there is a marine electrician/or electronics person who can advise.

It is easy to underestimate the thickness of cable that is needed to minimise current loss. And other things can add to iit such as cables bunched or heat and corrosion.

 

[Georgio]

Thanks all, much appreciated. Good idea from Jabs about changing the steaming light bulb to an LED, I can then use a smaller cable. I think I'll go 1mm to be on the safe side, that should be plenty.

 

[Enya]

A word of caution - do not assume that an LED bulb conversion uses as little current as a NASA purpose built one.