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Author Topic:   Wire for Navigation Lamps
Binkster posted 05-10-2014 07:17 AM ET (US)   Profile for Binkster   Send Email to Binkster  
What size wire is needed to run the navigation lamps on a 15-foot Whaler?


jimh posted 05-10-2014 07:54 AM ET (US)     Profile for jimh  Send Email to jimh     
Use at least 16-AWG wire as a general rule for all wiring on boats.
jimh posted 05-11-2014 01:34 PM ET (US)     Profile for jimh  Send Email to jimh     
One might be tempted to think of an incandescent miniature light bulb in a navigation lamp to be a low-current load, and, correspondingly, to not give much thought to the voltage drop in the branch circuit that feeds power to the lamp. However, the light output from an incandescent light bulb varies quite rapidly with voltage, and a small increase or decrease in voltage produces a change in light output that is greater in proportion than the change in voltage. Since the light produced by navigation lamps is required to have a certain intensity in order to meet visibility requirements, the voltage provided to the lamps should be carefully considered, and any source of voltage drop in the circuit should be minimized.

Concern for voltage drop is a good reason to use wire of 16-AWG conductor size for navigation lamp wiring. We know (from Hebert's Rule--a very useful rule of thumb that your author developed) that a conductor of 16-AWG can be run up to 12-feet with a voltage drop of only 3-percent (at 12-Volts) for a current of up to 3.7-Amperes.


A current capacity of 3.7-Amperes should give good margin for voltage drop in the circuit affecting the light output of the light bulb in the lamp.

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