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Old 01-05-2012, 01:12 AM   #1
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Re: 12 volt

Just run another wire back to the bus bar. It should be easy since you have already ran the one wire that way. I like to use color coded wires - red is hot, black is ground so it may mean that you have to get another roll of wire. I have also color coded separate hot circuits to keep from getting confused trying to trace a run. This was from my days in the Airforce when I had to build wiring harnesses for some of our equipment. It really sucked when you had a 100pin connector that every wire looked the same and each pin did something different.
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Old 01-05-2012, 08:19 AM   #2
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Re: 12 volt

Quote:
Originally Posted by RavensOracle
. . . . I like to use color coded wires - red is hot, black is ground . . . .
Except when you get into trailer and 'Stick-n-Staples' RV wiring, where black is hot and white is ground like AC wiring - be careful when mixing and matching equipment.

If you only have one battery string, using the vehicle chassis as your ground should not make any difference. If you have multiple strings, say four 6-volt house batteries in 2+2 configuration, it may make sense to use a bus bar to keep the battery wiring resistances nearly equal in order to balance the charge and discharge rates between the pairs. Plus, if you use battery capacity metering like a Tri-Metric, you will need to have a special large capacity/minute ohms resistor between the battery minus and ground in order to develop the signal to the meter. Having a battery ground bar insulated from the chassis is one way to have a place to connect the metering resistor.

The difference between solid and stranded wire has been debated here before. There is no specific conclusion, only what each person feels is most comfortable with for their bus. There is, as always, a cost versus quality decision to be made.

A number of RV manufacturers use solid house-type wiring in their AC wiring, and have the RVIA/NFPA specs written to accept it. In general, solid wire is to be used in places where the wire is bent once for installation, and does not move again after that. Solid wire that is bent back and forth will eventually break, just like snapping a piece of coat hanger. Some skoolies worry about road vibrations, and will not use it.

Wire that is meant to be bent, like extension cords, is instead made up of many strands of smaller conductors bundled together. Some stranded wire has a few thick strands, other wire has many, many fine strands. The smaller the strands that make up the bundle, the more the wire can be bent back and forth without harm. Wires for permanent fixtures probably don't matter, wires for accessories that move around like laptops or table lamps should definitely have stranded wire. The same is true for battery or generator wiring if there is a slide-out tray that requires the wires to move.

A word about stranded wire - if you see bare copper-colored strands inside the insulation, the wire will not be moisture resistant. I have seen my share of wires where any compromise of the plastic jacket that lets in moisture, even smaller than a pin-hole, lets the moisture turn the soft copper wire into hard, green powder. This powder will show voltage OK on a sensitive meter, but will not allow enough current through to run anything at the other end. I am not talking about "cord," where several wires are run together inside another protective jacket, but single-conductor colored 'hook-up' wire purchased from the auto parts or Radio Shack store. If the wire is "tinned," showing silver-colored conductors where the copper was bathed in solder before being put into the insulation, the wire will be more moisture resistant and last longer. It will also be easier to make solder connections to, as the solder has already been flowed into the molecules of metal in the wiring. (Solder is not "glue," but is a metal-to-metal bond.)

Good connections are much more important at low voltages than at household AC levels. A 21-watt turn signal bulb used for lighting draws 1.75 amps at 12 volts. A 25-watt incandescent AC bulb only draws 0.2 amps at 125 volts. A two-ohm resistance from a bad wiring connection would create 2.7 watts of heat and dim the DC bulb by about 25%, but at AC the heat would only be 0.4 watts and there would be no noticeable affect on the brightness. The same 2 ohms on a 12-volt, 600-amp starter cable would create 72 watts of heat, and limit the starter to 6 amps. If the connection were only half an ohm, it would supply 24 amps to the starter, generate 288 watts of heat, and give the impression of a dead battery until the fire started.

Some Skoolies will spend extra money and only use marine-grade wiring on their buses, with smaller strands and presumably higher quality insulation. They feel the extra money buys peace of mind. This may be a little bit of overkill for most of our purposes. But paying attention to what kind of wire we use, plus using zip ties, tubing, or other supports to prevent unwanted motion of the wires will go a long way toward making safe and reliable wiring.
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Old 01-05-2012, 11:33 AM   #3
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Re: 12 volt

Above post is correct of course. esp about color code for wiring.. In my case, I got a integrated electric control panel, and all wiring out of a monico coach which has the generator feed, land feed, switchover and fused panel for all 110v and 12v leads, including all tanks, etc. This makes wiring a bus very simple.
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Old 01-05-2012, 11:50 AM   #4
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Re: 12 volt

A cheap way of getting good stranded wire is to use heavy (12 & 10 ga) extension cords (what we are doing since we have many extension cords left over from our prior occupation). Even Fred Hobe (pro coach converter) uses extension cords... and they are neatly packaged together if you need them like that. All those green Christmas cords should be on sale now.

As for the ground bar. The one in the Blue bird is real nice. It's also filled up and grounded to the frame. Since we only need the battery bank and the AC/DC panel box grounded, we will ground those to the frame. Everything electrical will go thru the panel box.
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Old 01-05-2012, 12:19 PM   #5
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Re: 12 volt

Quote:
I have ran one wire for my 12 volt. I had planed to ground to the body because it is grounded to the frame.
This will work fine, just like an 'automotive' system - at least when they used to make cars outta metal
Quote:
Do I have to take out the 12v wire I ran and replace it with 12 RV two strand wire?
Nope. No need for a separate ground wire to each fixture.
Quote:
And where can I buy 12v RV 2 strand wire at.
Don't need the second conductor -just doubles the cost.

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Old 01-05-2012, 08:33 PM   #6
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Re: 12 volt

Geesh Lorna. On some bus sites, recommending the use of extension cords for fixed wiring has caused many a battle.
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Old 01-05-2012, 09:14 PM   #7
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Re: 12 volt

Quote:
Originally Posted by bus-bro
Geesh Lorna. On some bus sites, recommending the use of extension cords for fixed wiring has caused many a battle.
Quote:
http://users.cwnet.com/thall/fredhobe.htm
"Tips from a Pro"

" I donít post much on the BB's as most take it off, thinking that I am advertising. I have put on free seminars at my shop for the people that are converting a coach and want to do a good job and do it right. Twelve years ago there was very few coaches being built . And fewer builders to get advice from. Now with all the BB's and BCM everyone is trying to build a coach, and a lot wonít ask for help. It hurts me to see so many poorly built coaches out there.

These tips are only one way to do these things. Use them to get yourself thinking and as a starting place. I know that there are hundreds of ways to do all these things some better than others. I look and try to do each coach a little better than the last. To build one is a learning curve. If I can get those who read these tips to start thinking, then you can make improvements and you will have a lot better coach."

Fred Hobe

Way to save money on wiring
I buy 100 foot extension cord when they're on sale number, 12/3 conductor wire size. I can get them for as little as $15.00 and they come in different colors. I get several different colors and use yellow for air conditioners, orange for lights, black for wall plugs (120 volt) and green for 12 volt. They are UL approved and very flexible. You need to tin the ends when you hook them up to your main and on other connections use High lugs. Use an indent sqeezer to make good connections. You can buy 100 ft. cords with plugs on them cheaper than you can buy the wire by the foot. I use about 500 ft. of wire on a coach.


This shows how wires are run in the roof. Run them were they will come down the wall to the fuse panel.
For starters, I take Fred Hobe (North Florida Conversions) advice over many others.
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Old 01-05-2012, 09:38 PM   #8
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Re: 12 volt

There are several reasons not to use extension cords, your picture represents #1. The cords are bundled together & extension cords aren't rated for that. Too much heat for the insulation.
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Old 01-05-2012, 09:43 PM   #9
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Re: 12 volt

I use flexible cords, but wouldn't use it in a wall cavity as shown in the picture above. Mine run through compartments and in open air.
The insulation isn't rated for the temperatures that might be encountered in enclosed spaces carrying near max. current, and while it probably wouldn't really cause a problem in a wall with light loading, imagine one run just inside the roof, inside an enclosed ceiling, providing near limit current to, say, a roof air conditioner.

As to Fred Hobie saying
Quote:
They are UL approved and very flexible.
well, flexible cords might be UL listed, but not for that application shown in that picture. You have to read what it's listed FOR and use the device or appliance in that manner. If an electric heater is UL listed, it's listed for use as a heater - it doesn't mean that you can turn it face up and cook breakfast on it and that's OK because it's 'UL Listed'. Have never heard of Fred Hobie, but looking at that picture I don't think I've really missed much.

Ah, bus-bro slid in ahead of me just as I was writing this - I agree with him.

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Old 01-05-2012, 10:18 PM   #10
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Re: 12 volt

wtd, you said it so well.
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