Jan_Newt
Concord, NC
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Joined: 03/08/2008
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I am an idiot when it comes to electrical matters so I don't really understand the why of it but from years of operating a trolling motor on a boat, I have found that unlike A/C current, with D/C you get more efficient use from a battery using the largest possible wire over the shortest distance.
D/C apparently suffers loss based in large part on wire size (smaller = more loss) and distance (longer = more loss).
I do know that I can get at several hours more use from a battery charge using 8 gauge wire from battery to trolling motor than using 12 gauge over a distance of about 20 feet.
Jan & Newt, Concord, NC
USCG-Ret in '94
Will be retired, retired real soon now and full timing it
2007 Keystone Raptor 3600
2001 Ford F-550
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SOUTHERNSAGE
MOBILE, ALABAMA
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Joined: 10/06/2007
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What you call waste for using 12g wire is not correct. 12G is not much more expensive per roll than 14G. On an assembly line it is more simple to have one wire size than to change constantly. Also, leaving a foot or so play in a line is good practice. Nothing worse than trying to change a fixture with the service wire being short. I, and most others, use 12G for all 110V work and leave some extra length as general practice.
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sirdrakejr
Las Vegas, Nevada
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Joined: 11/18/2001
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Moved from 5th wheels to Gen'l RVing Issues.
Frank
RV.net blog
For those of you looking for expert advice, here ya go!
Frank
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Bumpyroad
Virginia
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Joined: 12/01/2005
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I'm more concerned myself with cows passing gas and harming the ozone layer. 
and 15 ft of 6/3wg? what did they do have it coiled up?
bumpy
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itsalleasy
USA
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Joined: 07/20/2007
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Vulcaneer wrote:While I do agree that RV manufacturers could use shorter wires, I wonder if they have a standard wire harness for all models.
I think you are close. I can't imagine a factory running each wire as in a building, RVs aren't unique. It is easy to build a standard harness that is used in different models with different options. Owners have been happy to find power for an air conditioner or ceiling vent where a non powered vent was installed.
When you consider the amount of wiring in a RV it would be a big task to eliminate or add wires. And if the harness didn't have a wire for an option it would be a huge job to add it.
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javaseuf
Southern Cal
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Joined: 03/30/2005
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Ok. Once again...................
When I was building Class A's, we used a pre-made wiring harness that was built on a 40' table in the factory. The jig for the harnesses was designed to be used for all of the models and lengths of coaches we built. To take the time to change-out wire to different gauges would be time consuming in labor so the extra cost for the next gauge of wire is a wash as far as money.
Also, most manufactures that pre-wire their harnesses, make one harness for a mutitude of models so one model may have more of a load and require 12 gauge and another may only be a 23' coach with only two lights on the same wire and yes, could use 14 gauge but too expensive and time consuming to shut down an assembly line to change out reels of wire.
Steve
2007 Springdale 291RKL
2003 F150 King Ranch
2001 Dodge Van w/Wheelchair Ramp
1991 Palomino Mustang PUP
Eureka Timberline Tent
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"Politically Incorrect And Proud Of It" 
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tenbear
Northern Vermont, USA
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Several things govern the required wire size. One is the current rating of the fuse or circuit breaker protecting that circuit. Circuits fused at 15 amps should be a minimum of #14 wire, 20 amps require #12 wire. If a partial short develops with a smaller wire size it is posssible that the wire could become too hot without the fuse blowing. In the case of 12 volt circuits the voltage drop is important. A larger wire size than the minimum may be required to reduce the voltage drop to an acceptable level.
If you want to replace the wire with a smaller size you should take these into consideration and change the size of the fuse accordingly and make sure the voltage drop is not excessive.
2004/5 Four Winds Dutchman Express 28A, Chevy chassis
Subaru Impreza Outback
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