What size aluminum wire for 100 amp 240 volt underground service 200 feet from transformer?

Answer 1

It depends upon whether you mean 240 volts at the first end or the second end.

Assuming 240 volts at the source, and allowing no more than a 3 percent voltage drop over the 200-foot circuit, at 100 percent load of 100 amps, you would need a #1 copper conductor. You would only have 233 volts at the far end at full load.

Note that if the ampacity of conductors supplying your connection point is not sufficient, the "supplied voltage" on your new extension could be substantially diminished under load. For instance, if you are already 100 feet from the original 240 volts, your extension would have an effective circuit distance of 300 feet, requiring #2/0 conductors.

Answer 2

It depends on the voltage but on a 240 v system the volt drop could go to 5% at the maximum load current, which is 12 v, therefore the total resistance allowed is 12/100 ohms or 0.12 ohms.

The wire length is 600 ft for 0.12 ohms therefore the wire size should allow a maximum of 0.2 ohms per 1000 ft, which would be #3 wire if copper or #1 if aluminium.

Wire sizes are normally even so the answer for aluminimum is #0.

Answer 3

First, alum is not a metallic substance usable as a wire or electrical conductor. You probably mean aluminum and should be aware that they are not the same.

An aluminum wire expected to carry 50 amp power load (assuming 120 volts) should be a 6 AWG (guage) wire. For longer wire runs, the increased resistance may cause a voltage drop and a thicker wire could be considered. The same is true for a lower voltage than 120 volts.

Answer 4

To answer this question correctly a voltage must be stated.

A 300 MCM aluminium conductor will limit the voltage drop to 3% or less when supplying 100 amps for 300 feet on a 120 volt system.

A 3/0 aluminium conductor will limit the voltage drop to 3% or less when supplying 100 amps for 300 feet on a 240 volt system.

A 1/0 aluminium conductor will limit the voltage drop to 3% or less when supplying 100 amps for 300 feet on a 480 volt system.

As you can see the higher the voltage of the circuit, the smaller the conductor for that circuit becomes.

Answer 5

This is a voltage drop question. Without a voltage stated an answer can not be given. Also whether the run is three phase or single phase must be stated.

That said, and on the assumption that the the run is single phase, I will calculate for 120 and 240 volts.

A 1/0 aluminum conductor will limit the voltage drop to 3% or less when supplying 50 amps for 200 feet on a 120 volt system.

A #3 aluminum conductor will limit the voltage drop to 3% or less when supplying 50 amps for 200 feet on a 240 volt system.

The answer below this one using a #6 conductor at 120 volts would only allow a 10 amp load before the voltage starts to drop off.

Answer 6

Please use the Discussion Area to explain the significance of the "100 feet".

Answer 7

A 2/0 aluminum conductor, with an insulation factor of 90 degrees C, when supplying 100 amps for 200 feet on a 240 volt system, will work.

Answer 8

Buried or conduit #2/0 aluminum will exceed the NEC recommended 3% or less and provide a 2.72% drop

Increasing to 3/0 provides a 2.26% drop

Make sure you resize your ground.

Answer 9

There is not enough information to answer this question. What is also needed is voltage, single or three phase and whether the installation is direct bury, overhead, or in a conduit system.

Answer 10

AWG # 4/0 alluminum or AWG # 3/0 copper