Voltage Drop vs distance chart available?

[Smart $]

Underground and concrete poles so ambient temp is a non-issue.

Oh, but it is. Consider the following...

R2 = R1 [ 1 + α (T2 – 75)], where α = 0.00323 for Cu. See Table 8, Note 2.
T2 = I^2 ? Iampacity^2 ? (75?C – Tambient) + Tambient ***You won't find this one in the NEC***, where Iampacity is 75?C ampacity adjusted for Tambient.

Therefore,

T2 = 10^2 ? (65 x 1.10)^2 ? (75 – 20) + 20 = 21?C, when Tambient is 20?C and assuming a 1.10 ampacity correction factor.
R2 = 0.44 [ 1 + 0.00323 ( 21 – 75)] = 0.36, using effective Z @ 0.85 PF from Table 9

Plugging R2 into your formula,

Vd = 2 ? 0.36 ? 620 ? 10 ? 1000 = 4.46V

 

[138lawfull]

Voltage Drop Caculator

Voltage Drop Caculator

Check this site out it was forwarded by a seinor engineer for LA Co..
www.cgsnetwork.com/voltagedropcalc.html

If anyone is good with this stuff, let me know how accurate it is. It asks for you to punch in 1/2 the distance??

 

[brother]

You figure power factor into I. In this case P/F was .85.(I use .9 when it's unknown)

I have 1800W of metal halide. 1800?208=8.65A. Actual load is 10A(all measurments taken with 2 Greenlee CM-850's). 8.65?.85=10.18A

Underground and concrete poles so ambient temp is a non-issue.

I couldn't get to the pole I wanted to because it was swarming with POed bees??? I took readings on the 2nd longest cir. and found this:

L=620' this includes wire up the poles
R=.491 #6 cu Chapter 9 Table 8
I=10A

VD= 2 x 0.491 x 620 x 10 ? 1000 = 6V

Actuall readings with a CM-850 at source and last head at the same time:

Source = 210V Furthest head = 206V

Difference between my calc and reality = 2V. Closer than I thought it would be.

where are you getting .85 for the power factor? why do you use .9 when its unknown?? Im still learning this stuff so i appreciate any info. I posted different formulas before and was curious as what others used. I normaly used the on the ugly's book

uglys book formula
vd= (2 x K x I x D)/cm single phase
vd= (sqroot of 3, x K x I x D)/cm 3 phase

k=12.9 resistance for copper , k=21.9 for aluminum

Its a basic formula but its pretty accurate and close enuff.
I also noticed you used 'UNCOATED' column, can some explain the difference in THE Coated and UNCOATED columns. I always used the uncoated if i ever use this column but like i said i always used the ugly's book formula

 

[brother]

this is also a good site.

http://www.elec-toolbox.com/Formulas/Useful/formulas.htm

 

[weressl]

IMO voltage drop calcs are a worst case scenario. I fired up parking lot lights yesterday and my calcs said I would have 196V at the last 208V fixture. I have 204V there? Go figure.

This is not the first time I have noticed this.

• Power factor is not calculated in those 'quickie' calculating methods. Ballasts' power factors are widely varied.
• What was your starting voltage?

 

[chris kennedy]

k=12.9 resistance for copper , k=21.9 for aluminum

Can't hang out, going to dinner.

The .85 power factor is real time calc using lamp wattage vs. amps actually drawn on the energized circuit. I throw .9 in when dealing with ballasts because it gets me close.

I like the formula I use because theres no constant, instead a resistance figure for the wire size in question.

weressl, theres an example in one of my previous posts on this thread.

Got to run.

 

[jrclen]

I couldn't get to the pole I wanted to because it was swarming with POed bees???

This time of the year I miss POed bees. They are all froze solid here. :grin: