A New Method to Calculate Voltage Drop, Wire Gauge, and Circuit Length

Electrical and electronic topics for small boats
jimh
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A New Method to Calculate Voltage Drop, Wire Gauge, and Circuit Length

Postby jimh » Sat Apr 03, 2021 10:09 am

Many boaters ask for recommendations on the proper wire size (as measured in American Wire Gauge or AWG values) to use for 12-Volt DC electrical power distribution. I have developed a very simple method to find the proper wire size. My method uses a pre-calculated table of the value of Ampere-feet for conductors of AWG-00 to AWG-16.

I explain the method in detail and how to use the table of values in an article at

Power Distribution--Voltage Drop Calculations
http://continuouswave.com/whaler/refere ... tion1.html

R DAVIS
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Re: A New Method to Calculate Voltage Drop, Wire Gauge, and Circuit Length

Postby R DAVIS » Sat Apr 03, 2021 11:12 am

Excellent article. Is there any significant difference when using tinned copper stranded wire?

jimh
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Location: Michigan, Lower Peninsula
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Re: A New Method to Calculate Voltage Drop, Wire Gauge, and Circuit Length

Postby jimh » Sun Apr 04, 2021 7:55 am

Thanks for the kind words on the article on calculating voltage drop with my Ampere-feet method. I hope you find it useful.

Re the resistance of copper wire that has been tinned: I doubt there is any significant difference compared to bare copper wire. The AWG gauge of the wire is a measure of its cross section. I suspect the bare copper wire is first drawn to a particular diameter, and then the tinning is applied. So a tinned copper wire would have the same or possibly less resistance at DC as a bare copper wire due to the same diameter cooper or maybe same diameter copper plus tinned surface layer.

The effect of the surface material of the wire is not a factor in the DC resistance. The “skin effect” only comes into play at radio frequencies.

The tinning is used to prevent oxidation of the copper wire. When exposed to the air with some water added, copper tends to transform chemically into a copper oxide. Copper oxide non-conductive. The presence of copper oxide on wire tends to cause many problems in interconnecting copper wiring, particularly on boats.

ASIDE: the nature of the numbering of AWG wire size is a reference to how many times the material has been drawn through successively smaller dies. That explains why the wire diameter decreases as the AWG number increases.