3/0 Gauge Wire Amp Rating (Explained)

3-0 gauge wire amp rating

3/0 is a size in the American Wire Gauge (AWG) system. It has the following attributes:

  • Diameter – 0.4096 Inches
  • Diameter – 10.405 mm
  • Cross-section – 85.0 mm2
  • Amps – 200A
  • Resistance – 0.23 ohm/km

3/0 Gauge Wire Amp Rating

3/0 copper wire can transmit 165 amps at 60 degrees, 200 amps at 75 degrees, and 225 amps at 90 degrees. While 3/0 aluminum wire can transmit 130 amps at 60 degrees, 155 amps at 75 degrees, and 175 amps at 90 degrees

Wire Gauge Size60˚C
3/0 AWG165200225130155175

How To Find 3/0 Gauge Wire Amps?

You find the ampacity by going to a wire size chart. The chart has a column showing the different gauges. Find 3/0 in this column and look at the corresponding rows to locate the amperage. If you find the wire size chart on a particular company’s website, ask them to specify the types of wires listed in their chart.

You typically find solid wires in wire size charts. To determine a stranded wire’s size, you should start by measuring the diameter of a bare strand. Use tables like the one on Engineers Edge to find the circular mils value in a row that fits the diameter you recorded. Multiply the circular mils by the number of strands before identifying the row in the table that comes closest to the answer.

You can also apply an ampacity calculator. These tools will ask for the material, wire type, ambient temperature, and the number of current-carrying conductors before revealing the 3/0 gauge wire amps. If you provide the wrong information, you will get the wrong answer.

3/0 Gauge Wire Uses

3/0 gauge wire is a great service-entrance conductor. A 200A capacity is significant, more than enough to run heavy-duty applications such as welding without overheating. You will also find this wire size in 12V and 24V batteries.

A 3/0 15-foot battery cable can tolerate 300 amps, especially if a manufacturer makes the conductors from pure copper. The only other AWG wire size bigger than 3/0 is 4/0. Therefore, you can trust it to run every conventional residential and commercial application you encounter.

Does Material Change 3/0 Gauge Wire Amps?

Most of the experts you consult will ask you to buy 3/0 copper wire instead of aluminum. But is that a good thing? Not necessarily. Copper is more expensive because of its superior durability and conductivity.

But what if you can’t afford the material? Aluminum is a suitable alternative because it has friendlier price tags. Admittedly, aluminum won’t last as long. The material will corrode quickly or become loose because of its inferior thermal expansion, introducing a fire hazard.

The key to safely replacing copper with aluminum is to get a thicker gauge. Have you seen the NEC’s wire size chart? 3/0 copper will carry as much as 225 amps. But that ampacity falls to 175 or even 155 amps when you switch to aluminum.

Aluminum cannot carry the same amps as copper. What happens when you increase the gauge? 4/0 aluminum will carry 180 amps at 75 degrees C, which is still disappointing. But that number jumps to 205A at 90 degrees C.

In other words, 4/0 aluminum can replace 3/0 copper if the application uses 200 amps. Usually, electricians will encourage you to increase the gauge by two sizes to replace aluminum with copper. This specifically applies to the AWG.

This standard doesn’t apply to wire sizes above 4/0 (Wire sizes that use kcmil). It is worth noting that some experts may discourage the use of 4/0 aluminum in place of 3/0 copper because 3/0 copper carries 200 amps at 75 degrees C.

4/0 aluminum can only match that capacity at 90 degrees C (205A). Typically, you should stay within the same temperature rating. Therefore, to replace 3/0 copper at 75 degrees C (200A), you should look to 4/0 aluminum at 75 degrees C. Unfortunately, 4/0 aluminum at 75 degrees C is insufficient.

This is why experts encourage consumers to jump up by two sizes when they replace copper with aluminum. This solves the temperature rating problem.

Does Cable Type Change 3/0 Gauge Wire Amps?

The cable type matters to an extent. From the wire size chart, you notice two things. First, the cable types go hand in hand with the temperature ratings. For instance, NM-B and UF-B appear under the 60 degrees C rating, but you don’t see them under 75 or 90 degrees C.

Second, there’s a lot of crossover between the cable types under 75 and 90 degrees C. Each cable type has different insulation, and the insulation types influence the temperature ratings.

Therefore, any decision you make regarding the gauge and ampacity will take the cable type into account. In fact, you determine the cable type before looking at the table. After all, the setting determines the cable’s insulation.

The jacket’s attributes should match the elements in the environment. Is the location wet? Do you expect to expose the wire to direct sunlight? Will you bury the conductors? Do you intend to run them through a well?

Will the lines encounter corrosive chemicals? You can’t proceed without answering these questions.

Does The Ambient Temperature Change 3/0 Gauge Wire Amps?

Yes, the ambient temperature is extremely important. A conductor can overheat because the load is too large. The rising resistance will produce more heat than the wire can handle.

A conductor can also overheat because of the ambient temperature. Does that mean you can’t run cables through hot environments with poor ventilation? Not necessarily. You can prevent fires by reducing the amps passing through the conductor, keeping the heat being generated under control.

But what if you have a sizeable load and can’t afford to reduce the amps? Buy a wire with a higher temperature rating. A higher temperature rating allows the conductor to transmit more amps without overheating.

Have you noticed that 3/0 copper can transmit 200A at 75 degrees C and 225A at 90 degrees C? A similar trend occurs with aluminum.

3/0 aluminum can withstand 155A at 75 degrees C and 175A at 90 degrees C. Normally, high temperatures increase the resistance, which, in turn, raises the voltage drop. A higher temperature rating overcomes this challenge.

This is why contractors perform a thorough analysis of the setting before selecting a wire. The environment influences the temperature rating.

Does Distance Affect 3/0 Gauge Wire Amps?

For Copper Wire,

Single Phase

VoltageAmpVoltage DropMax Distance
1201653%163 ft
2401653%326 ft
4801653%653 ft

Three Phase

VoltageAmpVoltage DropDistance
1201653%188 ft
2401653%377 ft
4801653%754 ft

Recent Posts