Help with Voltage Drop Calculation

[Little Bill]

I have an app for voltage drop but not sure that its right or I'm using it right.
Could someone run the numbers for me and see what wire size they come up with?
If you could, run both Cu & Al

Conductors will be in conduit outside in a trench.
400 ft run
240V
50A load

 

[Ingenieur]

assume 1 ph 3% drop = 7.2 v, R in Ohm/1000', NEC Table 9, PVC

7.2 = 50 x 2 x 400/1000 x R
R = 0.18 Ohm / 1000'

Cu: #2 AWG, 0.19 Ohm/1000'
Al: 1/0, 0.19 Ohm/1000'

 

[GoldDigger]

Using the Southwire calculator and assuming 3% max drop, single phase, and copper I get #1 for either direct buried or in conduit. Either of those should be good enough for your conduit in trench, I think.
For the same conditions, aluminum would be 2/0.
Both with a voltage drop of 2.48%

Using 3-phase instead, I still get 2/0 Al for 2.36%, but copper moves to #2 for a drop of 2.64%

 

[Ingenieur]

Using the Southwire calculator and assuming 3% max drop, single phase, and copper I get #1 for either direct buried or in conduit. Either of those should be good enough for your conduit in trench, I think.
For the same conditions, aluminum would be 2/0.

the program likely must be below 3%
mine are slightly above 0.19/0.18 x 3 = 3.17%
in this case I could live with it since both are so over-sized to begin with lol

when I run southwire
actual 3.04%, #2 Cu
actual, 3.47%, 1/0 Al

who is paying? lol

 

[GoldDigger]

the program likely must be below 3%
mine are slightly above 0.19/0.18 x 3 = 3.17%
in this case I could live with it since both are so over-sized to begin with lol

when I run southwire
actual 3.04%, #2 Cu
actual, 3.47%, 1/0 Al

who is paying? lol

The Southwire Calculator forces you to input the desired %VD (when starting with a known wire length and looking for size), and I just took 3% exactly as a plausible well known figure to draw the line at.

 

[Ingenieur]

The Southwire Calculator forces you to input the desired %VD (when starting with a known wire length and looking for size), and I just took 3% exactly as a plausible well known figure to draw the line at.

I adjusted the desired % in 0.1 increments until it produced #2 and 1/0 just to see how close I was
the 3.04% and 3.47% are the actual drops it calculated

my hand calcs required 0.18 Ohm but I used 0.19 since it was closer than the next size(s) up
that results in an actual 3.17% for both Cu and Al by my calc

I wonder how much difference the 0.85(NEC) vs 0.90 (sw) pf delta made?

 

[Little Bill]

Thanks guys!