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Thread: 12 volt distribution system for house.

  1. #1
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    12 volt distribution system for house.

    If you were going to have a battery system with your PV array, would it make sense to have a 12 volt distribution system in the house to avoid inverter losses? At minimum, lighting at 12 volts would be easy and comparable in quality to 120v lighting especially if LED. It works well in RVs.

  2. #2
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    Quote Originally Posted by Coppersmith View Post
    If you were going to have a battery system with your PV array, would it make sense to have a 12 volt distribution system in the house to avoid inverter losses? At minimum, lighting at 12 volts would be easy and comparable in quality to 120v lighting especially if LED. It works well in RVs.
    I would think depends on load(s). VD is a bigger problem with only 12 volts. Supplying lights only, you may get away with it easier though.
    I live for today, I'm just a day behind.

  3. #3
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    Quote Originally Posted by Coppersmith View Post
    If you were going to have a battery system with your PV array, would it make sense to have a 12 volt distribution system in the house to avoid inverter losses? At minimum, lighting at 12 volts would be easy and comparable in quality to 120v lighting especially if LED. It works well in RVs.
    Most battery based inverters do not operate at 12V; most of the older ones are 24V or 48V and some of the newer ones operate at much higher DC voltages. On a 24V or 48V inverter you could theoretically tap into a battery chain and get 12V, but at least with lead acid cells this would be a very bad idea. It is important for battery longevity that they all get the same charging and discharging treatment.

    In any case, inversion losses are pretty small. IMO it isn't worth doing.

  4. #4
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    The important thing is to size your inverter properly. Oversizing will result in less efficiency. Look at efficiency curves for inverters that you're interested in. You will note that they approach their optimal loading.

    You could do a 12 volt system for lighting and use LED modules. You would experience the most power savings there.

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  5. #5
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    I don't know how to edit on the app. I meant to say the efficiency approaches 100% at optimal loading.

    Sent from my A574BL using Tapatalk
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  6. #6
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    Quote Originally Posted by Coppersmith View Post
    ... It works well in RVs.
    And whether your desired loads are limited to quality
    products readily available for the RV market would be an important factor.

    I think it might make sense for a system that will no connection to the grid whatsoever. Almost certainly not otherwise.

  7. #7
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    There are a few things I would likely run dedicated 12 volt lines for: refrigerator, freezer, circulator pumps.... But except for maybe the smallest systems, I wouldnt run lights at 12V anymore. There is a great little 300 watt inverter, the morningstar suresine, which has super low idle and standby current. Your typical larger inverter is actually pretty harsh on idle and standby losses. I would entertain the idea of using the suresine for lighting and general use outlets, and using a big inverter only for things that really need it.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  8. #8
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    Unless it's a very small house, I²R losses will exceed inverter losses.

  9. #9
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    There are 24 volt lights, including light bulbs that can be used in your old lighting fixtures, as well as 12 volt lights. However, there are as yet no cieling fans with lights in either voltage but you can buy cieling fans in 12 volt, and wall fans in both voltages, along with refrigerators, freezers and even one washer so far in 12 volt.

  10. #10
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    I think that overall it is a bad idea. it limits the homeowner to using either landscape or RV lights in their home, for the most part anyway. Inverters are available these days with very low losses. As others have mentioned there are not all that many serious PV systems running 12VDC anymore anyway.

    OTOH, if the HO wants to pay you to do this after you have explained in writing that it is a bad idea, feel free to go ahead and do it. It will just mean someone else will have to fix it when they sell and the new HO finds out the mess that was left.

    You can run 12 V for appliances but most of them do not get used enough that the HO will ever see any return on it. Buy very high efficiency 120V appliances instead.
    Bob

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