What gauge wire do I need to use for a 250 ft. run from the power pole to a trailer with 110 - 30 amp service?

Question

What gauge wire do I need to use for a 250 ft. run from the power pole to a trailer with 110 - 30 amp service?

Answer 1

Are you sure that's 120V.?

Then you need #6 cu. for acceptible voltage drop.

Answer 2

according to nec code for sizing feeder conductor you have to consider two things: ampacity and voltage drop not to exceed 5%.

ampacity using THW 75C conductor

#10awg--- 10,380CM --- 30A ampacity --- okay

# 8awg --- 16,510CM --- 45A ampacity --- okay

# 6awg --- 26,240 CM --- 65A ampacity --- okay

# 4awg --- 41,740 CM --- 85A ampacity --- okay

calculate the voltage drop (V), V must not be more than 5%

V = (21.4)(L)(I) / (CM)

L = distance one way in feet

I = 30 ampere

CM = circular mils area of conductor

#10awg --- 16volt --- 16/110 = 0.1455 or 14.55% (no)

# 8awg --- 10 volt ---  10/110 = 0.091 or 9.1 % (no)

# 6awg ---  7 volt --- 7/110 = 0.064 or 6.4% (no)

# 4awg ---  3.8 volt --- 3.8/110 = 0.0345 or 3.45% (okay)

therefore to meet the ampacity and voltage drop requirements use

#4awg conductor