Quote: To all that are following this thread, as the OP I would like to invite any other electrical knowledge anyone is willing to post here, in the hopes this thread will become a great resource(it already has WAY surpassed my expectations!!!) for all of us, especially now in the age where we are getting into more and more sensitive electrical issues and systems. One thing that comes to mind would be charts like used to figure wire gauge for load and length, etc. Math used in electrical work is another. At this time I would also like to thank all that posted here with info. I appreciate it, and have learned a lot so far. Thanks, Greg
Here is the basic formula for wire sizing. I use it when designing boat electrical systems. With a composite boat, you are grounding back to the battery, similar to how Monte describes. The formula is as follows: CM = K*L*I/E
This will give you the wire required in what is called circular mils. There are conversions from circular mils to AWG on the internet
Now, here is the definition of the variables mentioned. K is a constant representing the resistance of copper, it is 10.75 ohms /mil-foot I = load current in amperes L = length of conductor from centre of distribution, in feet E = voltage drop at load, in volts
If it is a system where you have the ground going back to the battery, multiply by two.
Now, the rest is relatively straight forward. Load is given by the manufacturer of the device.
Length of conductor, get a tape measure and read it correctly.
Voltage drop: sort of like how fast do you want to go, how much do you have to spend? For a boat inspected by the USCG, you can have a voltage drop as high as 10%. The other standard in the marine world is 3% voltage drop. You want less voltage drop, there are three things you can do. One is to shorten the length of the run. This has the advantage of using less wire, which is less cost and weight. Second is to up voltage. Third is to go to a larger wire size.
I have a spreadsheet written to do this, it was not hard to create.
I use tinned marine grade wire wherever possible, and the end connectors from Pacer or Ancor that have the adhesive heat shrink insulation.
Hope I have not muddied the waters too much.
Regards, Dave
Would you consider the tinned marine grade cable a better conductor than say the solid copper SGX? I understand the tinning is for corrosion prevention?
