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  • Need opinion on wire size

    I have driveway post lamps put in 30 years ago, # 12 direct burial romex. I want to change the AC and use a total of 32 watts of DC on the 4 posts (8 watts on each post LED) The run is a total of 300 ft to my system. I have plenty of DC power just the question of will the cable carry the load.
    Thanks for your help

  • #2
    32w @ 12V = 2.7a
    So the cable will carry it just fine. But the resistance in the wire (300f + 300f) will drop your voltage from 12V to 9.4v (2.6v loss)

    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

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    • #3
      The capacity of wire is related to Amps. If you are running 12 volts then 32 Watts is less than 4 Amps. 12 gauge wire is good for 20 Amps. The big issue is voltage drop over 300 feet.and whether some voltage drop will affect your lights.
      9 kW solar. Driving EVs since 2012

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      • #4
        So having said that will the lights still function properly or perhaps I should buy a higher watt LED to make up for it. Right now I use 4 watt 110 and they look fine, Thank You

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        • #5
          higher wattage bulbs will increase the amps draw, which will lower the voltage more. Try it with the LED's you have, it's possible the driver circuits will compensate and they will work fine., or they may be dim, or they may blink. !!
          Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
          || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
          || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

          solar: http://tinyurl.com/LMR-Solar
          gen: http://tinyurl.com/LMR-Lister

          Comment


          • #6
            thanks for all the help, I bought the 12 volt lights and they work fine !!!

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