Wire size

[AmzngGrace]

Wire size
So the mystery continues…
When I was reading about the size wire for my windlass and the length of my boat somebody says oh no you double it because the size of the wire is based on the total length which includes up and back for a red and black which doubles the length of my boat from 35 feet to 70 feet. Does that make sense or is it just the singular length from battery to windlass which is about 35 feet?
FYI The reason for my question is this drastically changes the cost of the wire because I would need bigger wire because of the increased total length.

[tkeithlu]

The correct size, both ways. The current is the same in the red and in the black wires. No need to double.

[Ziggy]

Total distance: battery to windlass and back.

[Ziggy]

Originally Posted by tkeithlu

The correct size, both ways. The current is the same in the red and in the black wires. No need to double.

True for safety. Not true for voltage drop.

[more]

Originally Posted by AmzngGrace

Wire size
So the mystery continues…
When I was reading about the size wire for my windlass and the length of my boat somebody says oh no you double it because the size of the wire is based on the total length which includes up and back for a red and black which doubles the length of my boat from 35 feet to 70 feet. Does that make sense or is it just the singular length from battery to windlass which is about 35 feet?
FYI The reason for my question is this drastically changes the cost of the wire because I would need bigger wire because of the increased total length.

simple from relay switch/baterry to windlasses
you must make keep voltage drop under 5% ideal is 3% and lower. if your real voltage drop under work drop to 10-10,5 this can destroy windlase motor Overheat wire in motor
https://www.calculator.net/voltage-drop-calculator.html

[tkeithlu]

I did manage to find a wire size chart that was in distance to and back. The one I usually use takes that in account, indicating 10 feet to the device the same as the other chaart said twenty feet in all.

Here's the one I use:

Click the image below to enlarge

[Cheechako]

Yeah, especially today, it gets real expensive. The only way around it is a dedicated battery up forward, and that has to be used correctly to work safely. Not a fan of it though.

[smac999]

Originally Posted by tkeithlu

I did manage to find a wire size chart that was in distance to and back. The one I usually use takes that in account, indicating 10 feet to the device the same as the other chaart said twenty feet in all.

Here's the one I use:

Click the image below to enlarge

Your comment is confusing. But that chart is total length both ways. So You need to use 70’ for op’s 35’ run.

[sailorboy1]

Voltage drop is for from the battery to the load and back. Whether you use the 1 way or 2 way distance depends on what the chart or calculator you are using.

[AmzngGrace]

The english language is so able to mystify and astound...
I believe you all are saying the same thing (?) in several ways.
What I am reading, (I think), is that when planning wire size I need to double the length. This will likely require getting a larger and more expensive wire.
Example:
35 foot boat with battery in back and windlass in front = 35 feet (example only).
35 feet of red going out and 35 feet of black going back. That does not equal 35 feet for wire size planning but indeed requires 70 feet of wire length to calculate the proper wire guage for the windlass that is only 35 feet from battery.

[GordMay]

See ➥ https://www.cruisersforum.com/forums....html#post1256

The industry standard formula for calculating minimum Wire Size for a given Voltage Drop is:

CM = (K x A x L) ÷ VD
Where:
CM = The Circular Mil cross sectional area of the wire
(See Table 1, and ABYC Section E-8, Table III)
K = 10.75 Representing the Mil-Foot Resistance of Copper Wire @ 78o F.
L = The Total Length of the wire in Feet
(This is the ‘Round Trip’ length of both Positive + Negative wires)
VD = Permitted Drop in Volts
(Ie: 3% @ 12.5V = 0.375 ED or 3% @ 25V = 0.750 ED)

[Lake-Effect]

The full article on wire-size, that goes with the above chart.

[Stu Jackson]

Originally Posted by AmzngGrace

>>>>>>
>>>>>>>>>>>>>>


This will likely require getting a larger and more expensive wire.
>>>>>>>>>>>>>
>>>>>>>>>>>>>

No, what it means is the other sizing was wrong and too small.


Using the total distance is Electrical 101, in every single book and online reference source.


www.bluesea.com also has good material on this and fusing, but it's a PDF download and doesn't link. Here's the link to the page, scroll down for the PDF download of the Fuse & Wire Sizing Tables: https://www.bluesea.com/support/reference

[AmzngGrace]

“Using the total distance is Electrical 101, in every single book and online reference source.”

Thank you for this friendly reminder that I need to know all the answers before I post anything to this forum.

[Frankly]

Sizing an electrical conductor is first based on ampacity considerations. Often on 12 Volt systems voltage drop rears its head and will require a larger wire size. All real calculations consider the complete conductor round trip (positive and negative/ return). If you are uncertain about Voltage Drop tables, just look up the conductor resistance (often given in ohms per 1,000 ft) and use Ohm"s law V (drop)=I(amps) x R (circuit resistance Ohms) and run the numbers.


Frankly