Help with Voltage Drop

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triplex15

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Virginia
I need help with voltage drop. I have a driveway that is about 2250 feet long. I will be installing 11 fixtures with 100watt metal halide fixtures using 240 volts. I will be installing wiring in conduit. With the price of Copper I am looking to run Aluminum. Any help would greatly be appreciated. Thank You
 
charlie b

charlie b

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One key way to reduce the costs would be to do a more complicated VD analysis that takes into account the fact that not all lights are at the end of the run. Let me, for the sake of discussion, presume that you place one light every 200 feet along the driveway. Then you have,
  • 1100 watts of load supplied by the first 200 feet of wire,
  • 1000 watts supplied by the second 200 feet of wire,
  • 900 watts supplied by the next 200 feet of wire,
  • etc.
What this does for you is gives you a lower overall VD than you would have gotten, if you assumed you had 1100 watts of load over the entire 2200 feet of the run. You can complicate things one step further, and reduce costs even more, if you use this process to let you install a larger wire at the beginning of the run, and smaller wires further down the run. You can do this calculation with a simple spreadsheet, or is it a small enough calculation to do on paper.

 
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BAHTAH

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Volt Drop

Volt Drop

triplex15 said:
I need help with voltage drop. I have a driveway that is about 2250 feet long. I will be installing 11 fixtures with 100watt metal halide fixtures using 240 volts. I will be installing wiring in conduit. With the price of Copper I am looking to run Aluminum. Any help would greatly be appreciated. Thank You
Click to expand...

I figured the first fixture at 20ft and then 223ft between fixtures. I figured the 100watt MH at 120watts (allowing 20 for the ballast). I figured a LCL of 1134ft and total load of 5.5amps@240V. I got 2.56% drop for #6CU and 2.64% drop for #4AL. Depending how you space your fixtures the LCL could change. Hope that is of some help.
 
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triplex15

Member
Location
Virginia
Do you have the formula you used that I could see the work. The first light will be about 150 feet from service and then about 180 to 200 feet between them. If I feed out of a sub panel does the allowable voltage drop change. Thanks
 
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BAHTAH

Senior Member
Location
United States
Volt Drop

Volt Drop

triplex15 said:
Do you have the formula you used that I could see the work. The first light will be about 150 feet from service and then about 180 to 200 feet between them. If I feed out of a sub panel does the allowable voltage drop change. Thanks
Click to expand...

Using 150ft to the first fixture and 210ft between the balance of fixtures with the same load it changed the LCL to 1200ft. I got 2.79%drop with #4AL and 2.70% drop with #6CU. Check your private messages and I will send you my Excel Program for VD and LCL calc.
 
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