[Alberg30] anchor light wiring

[Robert Kirk]

At 11:07 AM 2/11/03 -0500, George Dinwiddie wrote:
>An Aqua Signal series 25 light uses 10 watts.  At 12 volts, that's a 
>little less than 1 amp.  (watts = volts * amps)
>
>16 awg wire is about 4 ohms per 1000 feet.  The run from the electrical 
>panel to the top of the mast and back is probably less than 100 feet as a 
>guess.  So, the round-trip resistance would be about 0.4 ohms.  At one 
>amp, that's a 0.4 volt voltage drop (volts = ohms * amps), or a 3-1/3% 
>voltage drop.
>
>In reality, since the battery voltage is greater than 12 volts and the 
>current draw is less than one amp, you'll be under the 3% voltage drop 
>that's considered adequate for electronics, and considerably under the 10% 
>voltage drop that's considered adequate for lamps.


George... I disagree. I'm pretty cavalier in using wire nuts, etc, but on 
the other hand,  I believe you should always use heavy wire for all your 
circuits. For simplicity & safety sake I wire everything at 12ga in the 
boat (unless it needs more). It's much easier to buy one coil of fat wire 
and use it for everything. Then you don't have to calculate every circuit 
and have a big inventory of different sized wires. It saves time & worry.

16 is just too small to use,. It's not much more expensive to use 12ga and 
it solves a lot of problems.

The ABYC says:

    Conductors used for electronic equipment, navigation lights or other 
circuits where voltage drop should be kept to a minimum shall be sized for 
a voltage drop not to exceed 3% (See Table C). Conductors used for lighting 
(other than navigation lights) and other circuits where voltage drop in not 
critical may be sized for a voltage drop no to exceed 10%.

It's always nice to measure 12V at the end of every circuit instead of 
something quite a bit less.

  Here, I calculate your 16ga wiring gives a 3.3% voltage drop, or roughly 
half a volt, which is more than recommended for navigation lights. [16ga; 
100ft 2 way run; 12V; 1amp]

Wire is cheap and heavy 12ga wire takes up no more space and gives piece of 
mind. Don't forget you're going to lose some voltage in the connections in 
addition to the wire itself.

Bob Kirk
Isobar #181

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