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What's a good wire for 12vdc distribution ?

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    What's a good wire for 12vdc distribution ?

    I managed to get one of those 25amp 12vdc Radio Shack converters yesterday. Now I am wondering what wire would be considered good (safe) for distribution of 12vdc around my house. I would like to use the 12volt to run closet lights, etc.

    Also want to be able to use 12volt auto stuff in the house.

    Is there a standard for home low voltage power distribution ?

    SteveP

    #2
    Depends upon the load you are going to service. At 12 volts you are 10 times more sensitive to losses due to resistence of the wire. Bring in that 400 watt audio amp from the car with a 2 ohm speaker and you will have a significant voltage drop in the wire by the time it reaches the speaker. For safety you are at a 10 gauge. If you are really going to push it and run things like motors that are sensitive to voltage drops then you will want more margin, hence a lower number wire gauge. I do not know the unit you have, but it is probably a peak rating and continuous duty may be more like 10A. In actual service you may only use 1 amp. At 10 amps standard house wiring will work, but I do not know about the code with respect to how to identify a run of 12v vs 120v(rated at 600) after it is burried in the wall.

    You may also have problems of coupling with long runs of 12V if it is in the neighborhood of AC wiring. It is not easy to keep low votage wiring clean.

    Comment


      #3
      Here's the manual data Power Supply Manual.

      While it puts out a lot of power, I would only be using very small loads remotely. I would like to use things like those small flourescent tube lights that run on 12vdc. Other potentials include the 4 or 7watt outdoor yard type fixtures for small constantly lighting.

      I don't plan on bring the car stereo in house. I have another 5 amp unit for auto component testing.

      I just want to see what wire would seem appropriate to run through walls. I would fuse as expected at my devices and feed point.

      I haven't checked into the solar energy web sites yet but they might know as several seem to use lower voltages for lighting, etc.

      I know there are some real technogeeks on this board so I am hoping for some input. The folks here represent a great knowledge pool.

      SteveP

      Comment


        #4
        Steve,

        Running a 12V supply with such a large amount of current available "can" be dangerous. Even with 10-gauge wire, if the total resistance of that cable is 0.5 ohms or more (it depends on length), you could short out the cable and the supply would not trip! What it would do is heat up the cable. There is a potential of 300W being dissipated, which could obviously start a fire.

        IMO the correct way to distribute 12V is to feed each appliance (or small group of appliances) back to the PSU with a minimum 8-10 gauge cable (the thicker the better!) and fuse this cable no higher than 5 amps (lower if you can). You will then have the overhead to trip the fuse if there is a problem. This method will also reduce voltage drop as you are only drawing small currents down each cable.

        Jon
        Jon

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          #5
          curious, what do you hope to gain by doing this?

          Comment


            #6
            I was just hoping to use inexpensive lighting units for closets, stairways, hallways, etc. Also, as I have a fair amount of 12volt lighting I use for camping with my Boy Scout troop, I could put some of this stuff around the house for emergencies (power outages) and just plug it in to 12volts to provide lighting during power outages. I was planning on adding battery support later that could be used on this circuit by switching out the converter. In some cases, adding wall warts to put 12volts in a closet is real impractical (adding more 110 circuits) so it seemed to make sense to try to centralize this. But now I am beginning to wonder if it's just about wall warts.

            SteveP

            Comment


              #7
              Steve,

              The proper and safe thing to do is to install a fuse in series with the wire. There are several types of fuse styles to concider, but the snap in type is probably the easiest. Sum up the total current, or measure the total current when you have everything running, then install a fuse that is at or just above the maximum.

              Secondly, if you decide to go that route, you also need to think about building codes for low voltage wires. I don't remember the proper name, but the wire used for door bell circuits will probably be appropriate for the code requirements.

              As you said, your total power needs are not very high, but you have a a powerful supply capability. Limiting it with a fuse is appropriate, and not an expensive solution.

              regards,

              GenevaDude

              Comment


                #8
                If the US wiring is the same as this side of the pond, doorbell ccts are AC not DC... They also run at about 5v (or mine does anyway!)

                I'd also add that you might want to look at automotive wiring techniques. Providing you allow air to circulate around the wire (i.e. not bury it, but perhaps lay it under a carpet or something similar) you'd get away with trailer cable. 7 cores, split them 50/50 (well, 3-4) so you can individually fuse cores and limit currents to specific cct runs (rather than one big fuse for the whole house)...

                Good luck!

                David

                Comment


                  #9
                  I am trying to check out the guys that do solar. They usually have the battery banks at 12 or 24v. They do convert to 110 but I have found some that still use low voltage lighting and other small things. I hope to get some help from them.

                  SteveP

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