voltage Drop help

[triplex15]

What is the formula and best way to figure voltage drop for a 20amp circuit 120v feeding driveway lights 1200 feet away. The wire will be in PVC conduit and the total amperage for the fixtures will be 12amps. Thanks

 

[bob]

What is the formula and best way to figure voltage drop for a 20amp circuit 120v feeding driveway lights 1200 feet away. The wire will be in PVC conduit and the total amperage for the fixtures will be 12amps. Thanks

What kind of load do you have? Lights, motor, electric heat? A 3 wire ckt of #3 cu results in a 3% VD.

 

[triplex15]

The load is lights.
Thanks

 

[K8MHZ]

Here is a calculator

http://nooutage.com/vdrop.htm

It shows a 6 percent drop using 3AWG CU on a single 120 VAC circuit. A 120/240 circuit is needed for 3.1 percent. In effect you have 2 120 volt circuits with 6 amps on each if balanced properly.

 

[triplex15]

Thank you for that can you explain how to figure up voltage drop as you go farther and the load decreases. For example if I go the 1200 feet and then they add a 2 amp light load 600 feet farther down. THanks

 

[Smart $]

Thank you for that can you explain how to figure up voltage drop as you go farther and the load decreases. For example if I go the 1200 feet and then they add a 2 amp light load 600 feet farther down. THanks

One method is to find what's called the load center. Multiply each load by the distance from the source. Sum the preceding and divide by the total load.

For example, 1200ft ? 12A + 1800ft ? 2A = 18000ft-A... ? (12A + 2A) = 1286ft

Use 1286ft and 14A to calculate your voltage drop and determine wire size necessary for the entire 1800ft run.

Some methods use differing size wires between load points...

 

[cadpoint]

One method is to find what's called the load center. Multiply each load by the distance from the source. Sum the preceding and divide by the total load.

Some methods use differing size wires between load points...

Here is another one part of the example as Smart stated it.

American Electrian Handbook