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  1. #1
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    May 2012
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    Default eletric run over 500 feet

    I want to run electric from my house to a pole barn about 160 feet away and put a box in the pole barn to run to five pole lights about 360 feet down the driveway. Each pole light will draw about 240 watts. so I need to know what size wire and what amp breaker to run from the house, and what size wire and breaker to run from the barn to the lights?

  2. #2
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    Default Re: eletric run over 500 feet

    What type of lights and what wattage are they.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  3. #3
    Join Date
    May 2011
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    Default Re: eletric run over 500 feet

    With AC power the distance shouldn't be an issue other than the cost of copper. I would put a small subpanel in the pole barn. That first run then would be 220VAC. IF you want higher output fixtures, you might look and see if they are available in 220VAC as well. IT would reduce the wire size and might cost less to install.
    1925 Two-Story Stucco Beaux Arts Neoclassical

  4. #4
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    Default Re: eletric run over 500 feet

    Quote Originally Posted by motoguy128 View Post
    With AC power the distance shouldn't be an issue other than the cost of copper. I would put a small subpanel in the pole barn. That first run then would be 220VAC. IF you want higher output fixtures, you might look and see if they are available in 220VAC as well. IT would reduce the wire size and might cost less to install.
    Sorry but distance does make a difference, a voltage drop can be expected on long runs. If the circuit is only going to be used for incandescent lights it may not be a problem it would just cause them to be slightly less bright however some light fixtures have problems with lower voltage. As an example 500 foot 14 ga wire, 240 volts at 12 amps would have a voltage drop of over 31 volts which could exceed allowable tolerances of some solid state controlled devices.
    That is why it is important to know what wattage will be on the circuit to size the wires and figure the load to calculate line drop.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  5. #5
    Join Date
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    Columbiana, Alabama
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    Default Re: eletric run over 500 feet

    Kelly, if you run 120V/240V to a panel in your barn over #8 copper for 160 ft you will drop 2.5V at 10A leaving you 237.5V if you run 240V lights.

    Then, if you run #12 copper wire to five 120V 2A lights on evenly spaced poles for 360 ft from the barn (72 ft) you will have a 9.9V drop (8.21% drop) and 110.15V available for the last light, which should be fine.

    Remember the feed to the barn should be (2) #8 CU “hots” (1) #8 CU white (neutral) and (1) #10 CU green ground. It can be on a 40A 2 Pole breaker in your house.

    A small 100A main breaker (serving as a disconnect) (8) space (min) panel in the barn will allow you to run small loads there and feed the lights.

    The barn will require (2) ground rods and everything tied together to any metal piping w/ #6 (min. bare copper.

    Hope this helps

  6. #6
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    Default Re: eletric run over 500 feet

    Quote Originally Posted by The Semi-Retired Electric View Post
    Kelly, if you run 120V/240V to a panel in your barn over #8 copper for 160 ft you will drop 2.5V at 10A leaving you 237.5V if you run 240V lights.

    Then, if you run #12 copper wire to five 120V 2A lights on evenly spaced poles for 360 ft from the barn (72 ft) you will have a 9.9V drop (8.21% drop) and 110.15V available for the last light, which should be fine.

    Remember the feed to the barn should be (2) #8 CU “hots” (1) #8 CU white (neutral) and (1) #10 CU green ground. It can be on a 40A 2 Pole breaker in your house.

    A small 100A main breaker (serving as a disconnect) (8) space (min) panel in the barn will allow you to run small loads there and feed the lights.

    The barn will require (2) ground rods and everything tied together to any metal piping w/ #6 (min. bare copper.

    Hope this helps
    The calculation is a little off with only 237.5 volts to the panel and a 9.9 volt drop to the last light the voltage would be 108.5 volts. That is fine for incandescent lights but could be problematic with solid state controlled devices that call for 120 volts + or - 10.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  7. #7
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    Default Re: eletric run over 500 feet

    Quote Originally Posted by JLMCDANIEL View Post
    The calculation is a little off with only 237.5 volts to the panel and a 9.9 volt drop to the last light the voltage would be 108.5 volts. That is fine for incandescent lights but could be problematic with solid state controlled devices that call for 120 volts + or - 10.

    Jack
    I assumed the lights would be incandesant since they pull 240W.

    Jack did you just figure 10A for all of the 360 ft? That would only apply for the 1st 72 ft. So 5 calcs are req.

  8. #8
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    Default Re: eletric run over 500 feet

    Quote Originally Posted by The Semi-Retired Electric View Post
    I assumed the lights would be incandesant since they pull 240W.

    Jack did you just figure 10A for all of the 360 ft? That would only apply for the 1st 72 ft. So 5 calcs are req.
    I used your voltage drop figures.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

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