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rayncyn51 03-16-2009 10:23 AM

Voltage Drop
I am replacing the wiring harness in the mast. I have a tri-color and anchor light at the top (both LED), and a steaming light and some hefty deck lights at the spreaders. I've done a ton of research about voltage drop. I've found and used many of the tables referenced elsewhere here in Sailnet. It appears that if I follow the reccomended guage for AWG marine grade wire to achieve the suggested maximun 3 percent voltage drop, I would be adding roughly 10 pounds of wire in the mast. Compared to what has worked for the last 30 years, wiring that big seems a bit excessive to me. :confused: I would like to hear some thoughts about what works in the real world. Thanks in advance. - r

scottyt 03-16-2009 10:38 AM

i would say you want under a 1 volt drop, yea 3 % is electric code for houses and bussiness but as you have seen 3% on 12 system is hard to get. the lower drop you have the better, but it is a balancing act of too much weight vrs too much drop. this is why an led light is so great, it uses less so you can get away with smaller wire. i would play with the wire sizes to see where you get the best drop vrs the weight and find a middle ground.

btw this is also why you dont want to share neg wires on a boat, it can cuase too much drop when both things are on.

disclaimer i am a real sparky but not a boat one, so what i say may not be right

Maine Sail 03-16-2009 11:37 AM

With good quality LED's voltage drop is not an issue and 10% is fine. With incandescent lights 10% can slightly reduce the output but not by a whole lot. You won't hurt the bulbs by aiming for a 10% VD 3% is excellent.

SteveInMD 03-16-2009 09:27 PM

Use the tables for 10% drop for lights.

Gary M 03-16-2009 10:04 PM

LEDs use a very small amount of current, small nav lights use a little more but not that much. When you have a very small current flow you have very little voltage drop.
For both of these if running up a mast I use 18 awg to save weight. If you have powerfull spreader lights than you should go a little heavier.

Of course you could run out the lenght of wire and terminate it at your panel and try it to see if you are happy with the brightness before you install it.

AllThumbs 03-16-2009 10:07 PM

10 lbs? What size wire do the charts recommend? Go with the same size that was in there and sail your boat.


badsanta 03-17-2009 12:58 AM

if you run your wires horizontally to test voltage you should also take in account the vertical height of the mast and increase the pressure for loss in gravity and take in account atmospheric pressure and , oh heck that's hydraulics not ohms law, way too many formulas!

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