12 Volt Systems

Discussion in 'Energy & Electricity' started by Grizz, Mar 16, 2010.

  1. Grizz

    Grizz Well-Known Member

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    OK, I'm sure this has been covered here many times but i can not find it. I hear several of you talking about the dangers or draw back of 12 Volt systems. Can you point me in the right direction to past posts that cover this. Is the problem the system or bad workmanship or poor planning? I will begin construction in 3 years and i'm a planner and list maker and like to have things all planned in advance. I'm looking at as many propane items as possible ( fridge, oven, hot water, lights. With a modest solar and battery. I have several generators as back up, and to use when i need the extra power. Wood heat. I agree there are so many 12 volt items available and the technologies are always changing so i am prepared to change as needed. Thanks for any info.
     
  2. Tex

    Tex Pincushion

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    With a lower voltage like 12V, the amperage required for many tasks will be higher. This will require larger, higher capacity wiring. If your site is large, wiring may be cost prohibitive.

    I've considered a DC system for lighting. LED lights are very efficient. Having DC lights minimizes the need to run an inverter, which is about 92% efficient at best.
     

  3. GetPreparedStuff

    GetPreparedStuff Member

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    As I understand it the lower voltage is a blessing and a curse. At 12 volts, there is a much less risk of electrocution though anything with high amperage can be dangerous in a given condition. Besides safety, 12v has it's benefits because there are a higher number of devices made for that voltage because of it's general use in vehicles, trailers and RV's.

    It's limitations as mentioned above is that in order to wire a home or other large structure you would have to have use very heavy gauge wires for runs of more than 20-30 feet especially to power devices that had higher power requirements. Without the heavy gauge wire, the risk of hot wires and the voltage drop from the wire resistance at the lower 12v voltage are the problems you face. If the structure you are wiring is the size of travel trailer/RV then you should be OK, if it's any larger you will need to consider the pros/cons of converting your 12v DC to AC using an inverter which would let you use regular 110v wiring schemes. In a home this would likely be your best option. You lose some power to the conversion process but you can at least have access to power from one end of the house to the other.

    There are 24v devices available but they are harder to come by and more expensive but the higher voltage gives you the ability to run wires a little farther without running into problems.
     
  4. NaeKid

    NaeKid YourAdministrator, eh?

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    GetPrepared - I agree with you to a certain extent.

    You will find many RV's at 30' or longer that are running 16g to 12g wiring in the trailers without any significant power-loss through the circuits. When designing a 12-volt system in a house, just remember to put the batteries in the "middle" of the house for the shortest runs to the furthest extents of the building, run light-guage wire (16g) to low-draw items like LED lighting from a high-guage (10g) wired fuse-panel or power-distribution-block.

    For the "high-draw" items, have the power-source (batteries / solar / wind) as close as possible to those items to save on wiring costs.

    Setting up a 12-volt system can be as simple and cheap as someone wants to make it or as involved and expensive as they want to make it.
     
  5. sailaway

    sailaway Well-Known Member

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    Grizz, Look for the book, "Living On 12 Volt with Ample Power" it goes into alot of ways to wire up for using it. It's part of my sailboat library. You can also find alot of 12v. items in truck stops.
     
  6. robert

    robert Member

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    I have two friends that have been in the solar arena for over 30 years. They sell and install. Both say to start with either aa 24 or 48 volt system hooked up to an inverter.This of course is if your going to run cfl's and other appliences
     
  7. JeepHammer

    JeepHammer Well-Known Member

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    The biggest problem I see is pulling large amperage loads to power anything at 12 volts.

    To determine what size wire you need, you need to convert the loads into 'Watts' and use Ohm's Law to determine that.

    An appliance that uses 120 Watts will need to be wired drastically different between 120 volts or 12 volts...

    120 Volts X 1 Amp = 120 Watts.
    1 Amp can easily be transfered through 18 Ga wire with no problems at all.

    12 Volts X 10 Amps = 120 Watts.
    10 Amps will take a 12 Ga. wire to transfer it safely,
    AND COPPER IS EXPENSIVE!

    Remember, you have to use the LARGEST wire for all combined loads on that circuit, or you stand the chance of causing a fire if you plug in too much on that circuit!
    So EVERYTHING will need large wire if you go DC.

    For instance, a VERY SMALL microwave or hair dryer will draw about 1,500 Watts.

    1,500 Watts ÷ 12 Volts = 125 AMPS!
    That requires a 2 Ga. wire MINIMUM over short distances!
    (Conductor about the size of your little finger!)

    While that same appliance in 120 volt wiring,
    1,500 Watts ÷ 120 Volts = 12.5 Amps,
    And that's a 14 Ga. wire minimum, MUCH smaller wire and much less cost/potential for disaster.

    You should also consider availability of appliances.
    There are VERY energy efficient appliances available for 120 volt wiring,
    VERY FEW and VERY EXPENSIVE available in 12 or 24 volts...

    I would also reconsider using a propane refridigator or freezer.
    Propane, Liquid Propane Gas, is directly tied to oil prices and availability.

    A solar panel array and small battery bank, with or without inverter, would be a much better way to power things like well insulated freezers that can maintain freezing temperatures overnight without much power consumption.

    Sunlight is free.
    Batteries take up the slack over night,
    Generators can both run the appliances and charge batteries while running a VERY short time in the event of no sun for a few days...
    And the propane fuel savings will more than offset the cost of the solar/battery arrangment over time,
    Plus you aren't at the mercy of the oil companies.

    Instead of propane, Consider CNG (Compressed Natural Gas) for your 'Backup'...
    CNG isn't a byproduct of OIL, so the prices and availability are more stable.

    Another 'Back Up' is wind power.
    Most of the time, when the sun isn't shining,
    The wind is blowing like crazy here, so even though I'm in an area that is considered 'No Wind' zone,
    My little wind generator does a good job of toping off the batteries when the sun isn't shining...
    ---------------------------------------------------

    The biggest thing you can do for yourself is SAVE/CONSERVE!
    Passive Solar to heat the home as much as possible in the winter,
    Shade trees/vines, ect. planted to keep the house cool in summer.

    Evergreen trees planted on the north and west sides of the house to break up winter winds, lots of 'Low E' coated windows on the south facing side,
    Porches with a length that will allow low winter sun in the home,
    Keep the high summer sun out of the home.

    INSULATE LIKE CRAZY!
    The best thing I ever did was spend $5,000 on expanding foam insulation everywhere!
    Nothing beats a good, tight, draft free home with lots of insulation!
    I pay a lot to make heat in the winter, and having that heat carried off by stray drafts really torques me!

    It's only a few bucks to make some solar THERMAL collectors for your sun spaces (Roof of home, garage, shed) to take advantage of the sun for heating water or air for the home.
    Remember, they shield your shingles too, so your roof lasts longer!

    With a metal roof, I use rain catchment for 'Service Water'...
    Washing cloths, flushing toilet, watering critters, washing the car...
    Saves me a TON of money on the water bill in town,
    And at our river house that has utility services, it makes for some trouble free and cheap garden watering also.

    Drinking/Cooking water still goes through a big honkin' water filter,
    But the other water in the home comes right out of the holding tank buried out back.
    (Plastic tanks live a lot longer under roof or buried away from UV light!
    And buried tanks don't freeze up and split! Ask me how I found that one out... :( )

    At the river cabin, the well water pump virtually never runs,
    A testament to the 1,500 gallons of "Service Water" in 'Cistern' type tanks...
     
    Last edited: Mar 28, 2010