voltage drop in 80 ft run #4 wire?

May 2021 5 88 Report

voltage drop in 80 ft run #4 wire?

I need to move an rv can another 30 ft. The total run will be 80ft supplying 50 amp service. running 100 amp into can now. Will that work or do I need to change to a larger wire.

Also can I splice the #4 there now to extend it>

Thank Tommy

Science & Mathematics / Engineering

Anonymous

Verified answer

assuming 240v service

v = (2)(10.6)(D)(I) /CM

v = voltage drop volts

10.6 = copper resistivity 10.6 ohm per cir-mil-ft

D = distance one way in ft 80ft

I = current in amp 50a

CM = cir-mil of conductor

v = 84 800 /CM

#6 (26 240CM) --- drop 3.23v ---- 1.35%

#4 (41 740CM) --- drop 2.03v ---- 0.85%

#2 (66 360CM) --- drop 1.28v --- 0.53%

nec code said max 5% drop so your #4 wire is ok

do not splice service wire because most of the trouble is in the connection

Morningfox

4 copper wire has a resistance of 0.000292 ohms per foot. So 80 feet has a resistance of 0.02336 ohms. At 50 amps, that will be a drop of 1.15 volts. A splice might cause another drop of 0.2 volt, which would get slightly warm at 50 amps. Should be okay, but I can't say what you local electric code might say about it.

lare

electricity requires a complete circuit. so if the ground distance is 80 foot, then you are using 160 feet of wire to make the circuit. so count the voltage losses in both the supply and return wire. assuming we are distributing 120 or 240 VAC you should be ok. If this is a 12 VDC run, then probably not.