Voltage drop question for mini-warehouses

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ultramegabob

ultramegabob

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Indiana
I need a refresher on how to calculate voltage drop on a lighting circuit, my circuit will be 120v. 300' one direction, from the last fixture back the lights will be spaced every 40 feet the fixtures are 23 watt compact flourescents (buildings are staggard so lighting will zig zag every 20') do I just add the total load to do the calculation, or does the lights being spread over the lenght affect how to do the calculation?
 
The fixture spread will affect the calculation. See this thread about a series volt drop calculation:
http://forums.mikeholt.com/showthread.php?p=881172

You can use the by-section calculation or the load-center calculation. You would have a source and load voltage for each section but can use any volt drop formula you want (exact, approx, cmil, etc).
 
Did not feel like doing it earlier but here is the by-section sequence volt drop showing a total drop of 2.24853% using #14 and 100% power factor:

Section,amps,Type,Size,Section ft,Total ft,pf,Source,vd,Load,Section %,Total vd,Total %
1,2.7,Cu,14-1,20,20,1.0,120.0,0.34,119.7,0.28%,0.3,0.3%
2,2.4,Cu,14-1,40,60,1.0,119.7,0.59,119.1,0.49%,0.9,0.8%
3,2.0,Cu,14-1,40,100,1.0,119.1,0.51,118.6,0.42%,1.4,1.2%
4,1.7,Cu,14-1,40,140,1.0,118.6,0.42,118.1,0.36%,1.9,1.5%
5,1.4,Cu,14-1,40,180,1.0,118.1,0.34,117.8,0.29%,2.2,1.8%
6,1.0,Cu,14-1,40,220,1.0,117.8,0.25,117.6,0.21%,2.4,2.0%
7,0.7,Cu,14-1,40,260,1.0,117.6,0.17,117.4,0.14%,2.6,2.2%
8,0.3,Cu,14-1,40,300,1.0,117.4,0.08,117.3,0.07%,2.7,2.2%


or using the load center method:
Section,added amps,Total ft,section amp-ft,Total amp-ft
1,0.3,20,6.8,6.8
2,0.3,60,20.4,27.2
3,0.3,100,34.0,61.2
4,0.3,140,47.6,108.8
5,0.3,180,61.2,170.0
6,0.3,220,74.8,244.8
7,0.3,260,88.4,333.2
8,0.3,300,102.0,435.2
and 435.2/2.72 = 160 ft and
load center = 2.72 amps at 160 ft = 2.24853% with #14


And here is the volt drop using total amps and total distance (NOT the way to do it) showing a 4.216% drop:

Section,amps,Type,Size,Section ft,Total ft,pf,Source,vd,Load,Section %,Total vd,Total %
1,2.7,Cu,14-1,300,300,1.0,120.0,5.06,114.9,4.22%,5.1,4.2%
 
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