12 Volt Bible

[Roy M]

Duke 48, If you use wiring harnesses, don't forget to increase your wiring sizes per the guidelines for bundled wires. Using the Excel spreadsheet, it made these calculations almost automatic.

[Duke 48]

Roy M: I had already planned to increase wire size - 14 instead of 16, 10 insead of 12, etc. just in case I decided to add a loads in the future.. You mentioned guidelines for bundeled wires. Is this ABYC or other?

[Roy M]

Duke 48, Go to the West Marine Advisor page, look up their wire sizing pdf. Toward the bottom you will find the guidelines (ABYC???) for derating current capacity on bundles of wiring. At the risk of starting another flareup of the techies, electrons don't like the company of others, so they stage a work slowdown when forced to travel together in bundles of wires. It has to do with electrons punching their elbows into each others sides, crabbing about who's insulation is cooler, and gossiping about who is circulating around at CERN in Switzerland. Just size up accordingly and things move along with no heat generated or feelings hurt.

[GordMay]

A good rule of thumb for “bundled” wires is to de-rate the individual ratings to 80% (or upsize to 125%).

See also:
http://www.cruisersforum.com/forums/...boats-372.html

And:
http://www.cruisersforum.com/gallery...r&imageuser=79
&
http://www.cruisersforum.com/gallery...r&imageuser=79

[Duke 48]

Roy M, Having checked out the West Marine sight as you suggested, I must admit the recommended current reductions are much larger than I expected. I'm sure there is some overkill for safety consideration, but I fully intend to follow the recommendations.

GordMay, The rule of thumb will help in my preliminary estimates. And, the article "Ohm's Law & Boats" has added even more dimension to my simple rewiring project. Fortunately, this "redesign" is one of the issues I plan to address during the winter.

Also, I really appreciate the input I have received on this thread.

[Roy M]

Duke 48, My electrical panel covers a locker about 1 1/2 feet square and a foot deep. From this locker, several large conduits run to different areas of the boat, many through the engine room below it. Because of this limitation I knew I had to design a system that would be installed once, given how nasty it is to pull wire through conduits. After I had created the circuits and determined the wiring sizes and lengths, I started cutting different wires and cables, with some extra, and labelled both ends using the code I created. Then I could pull the Anaconda of copper through the conduit and bends, peeling off wires as they reached their individual distribution nodes. I was very pleased when it all worked out. I had the foresight to include some extra wires, of different gauges, for future, unknown, additions.