Question

what is the relation to find the maximum load DC voltage for wire ?

Answer 1

@osprey

Answer 2

I don't know of a "relation" off hand, but a wire is a conductor, so that a DC voltage could pass a lot of current. Current squared times resistance is heat. Heat can melt wires. So that's one thing I'd look at.
There is also the possibility that a very high voltage can cause electrical discharge - sparks etc.
More information about the q would help

Answer 3

This may help, I have been wiring a boat the last few weeks and the major determining factor is how much voltage drop is acceptable. In practice, you will never approach the theoretical maximum because that is just before the metal would fail
http://assets.bluesea.com/files/resources/newsletter/images/DC_wire_selection_chartlg.jpg

Answer 4

When you say "fail" do you mean melt ?

Answer 5

@osprey Usually it is the insulation and not the wire that will melt, also this causes havoc in a bundle where heat is hard to shed. The smaller signal wires that are not as well insulated melt and short together in a horrible mess if a larger power carrying wire heats up.

Another mode of failure is simply too much voltage drop to run the intended devices.

But now that I read the question again he asks for the "maximum load DC voltage" a little ambiguous as the load is usually Amps and Voltage is usually limited by the insulation, not the wire. If Amps are low enough Voltage is not a problem for the conductor.

Think of a bird sitting on a high tension (voltage) wire, since there is very little current due to the insulating quality of the air down to earth nothing happens to the bird. The same would be true of a thin wire, it could probably carry 100,000 volts and not really suffer because the insulator is so large and only minute current would flow from it.

Another factor would be temperature and the efficiency of heat removal. A wire under water in a glacial stream could carry more power than one running across a desert at noon or in an oven at 500 degrees.

Answer 6

bugman954
Wonderful ! Rewiring a boat ! absolutely brilliant. Electricity with water in the area presents, presumably, it's own challenges and demands of safety.
Totally agree about the failure due to the insulation meltdown possibility, and the possible mess and stink that would result. So, when the spec of the wire is being looked at, the insulation's heat "resistance" properties are important ?
do you rewire in dry dock, or in situ ?

Answer 7

@osprey It's a 1994 Luhrs sportfishing boat in the water in pompano Beach Florida, hopefully, we will be ship shape by Wednesday and we will be able to go fishing. Redoing the house power from the 4x4D batteries in the belly all the way up o the bridge, also significant redesign of power and charging circuits

Answer 8

@bugman954 It sounds like marine engineering with a spot of oceanographics and streamlined beauty thrown in

Answer 9

@osprey just finished a 12 hour day, mostly feels like sweat and body odor right now. New 6awg house battery circuit from bottom to top. Hopefully, we will be fishing on Wednesday.

Answer 10

@bugman954 what sort of fish is this ?

Answer 11

@osprey Last time was Kingfish, Bonita we released a Shark and a small Dolphin (MahiMahi not flipper). Hoping for Dolphin and maybe a Wahoo or two, we will see.
https://goo.gl/photos/Yq6FsJXk2AfBEojp7

Answer 12

@bugman954
Interesting ... to list the number of skills needed to operate what sounds/looks like a commercial fishing company off the coast of Florida ?
Tell you what ... it's pretty chilly North of Fl and the pictures are quite warming, if a tad "fishy" and "wet".
Is this the area where the "keys" - "Key Largo" etc are ... with the Bermuda Triangles lurking ?
Fl sticks out into the Gulf of Mexico doesn't it ?

Answer 13

The wires are rated in Voltage and Current. The insulation on the wires determines the Voltage rating and the wire size detemines the current rating. attached is a link to a wire size chart. http://www.cerrowire.com/ampacity-charts