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How Many Amps Can 12 Gauge Wire Handle? (Answered)

Written by Edwin Jones / Fact checked by Andrew Wright

how many amps can 12 gauge wire handle

We typically utilize 12-gauge wire for outlets, and often, the lighting circuit. If you’re wondering how many amps can 12 gauge wire handle, it typically has a current rating of up to 20 amps.

However, factors that increase the wire’s resistance may alter this capacity. If you want to learn more about 12-gauge wires, you should read this article all the way through.

How Many Amps Can a 12 Gauge Wire Hold?

The best way to know the amperage rating for 12 gauge wire, as well as other wire sizes, is to look at the NEC table 310.15(B)(16). This table specifies the recommended loads for every given wire size.

However, before we determine what exact amp a 12 gauge wire is rated for, let me first explain the various temperature values you might see in the chart.

Remember, those specific temperature ratings are recommended for various equipment. For equipment with less than 100 amps, check out the 60°C wire rating. A 75°C wire, on the other hand, is recommended for equipment rated at more than 100 amps, and a 90°C wire for substantially higher current.

To know more about 12 gauge wires, here are the various types you may come across when shopping for them. Let us determine the 12 AWG amp rating depending on their type of conductor.

Types of 12-Gauge Wire

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When buying a 12 gauge wire thickness set, you may see a rating of 12/2, 12/3, or 12/4. Generally, the first number determines the size of the wire, while the second number determines the number of conductors.

However, each wire set may have an additional ground wire, bare or with green insulation. For additional information, here are some of the three types of 12-gauge wires available on the market.

  • 12/2 wire

12/2 means the wire has two conductors at 12 gauge (a black hot wire and a white neutral wire) with one additional ground wire. This cable is mainly used for lighting and a standard 110 or 120V circuit.

Sometimes, it can have a red hot wire and be rated at 220 volts instead.

  • 12/3 wire

The 12/3 wire has three conductors (which include two hot wires, usually black and red, and a white neutral wire) with an additional ground wire. The 12/3 wire handle a high supply rating and is mainly used at 240 volts.

  • 12/4 wire

The 12/4 cable is another 12-gauge wire which consists of four conductors and a ground. Though rare, you may see these wires in branch circuit installations.

Types of Wire Conductors

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  • Copper

Copper is an excellent electrical conductor that has low resistance. A 12 gauge wire rated at 60°C can safely handle 20 amps. Furthermore, it can transfer 25 up to 30 amps of loads under much higher heat, or 75°C and 90°C respectively.

Similarly, a 14 gauge wire handle 20 amps of load capacity if the wire is rated at 75°C and made of copper.

  • Aluminum

Aluminum wires are one of the best alternatives for copper wires, since they are relatively less expensive. However, aluminum is not as effective as copper. As a result, if you use it in any application, you may need a thicker gauge to deliver more current.

With a 12 gauge 60°C aluminum wire, homeowners can safely use only 15 amps. Anything more than this rating may cause damage to wire insulation, resulting in a significant electrical problem.

For 12 gauge aluminum to handle 20 amps, it must be rated at 75℃.

As a result, you can use a high-temperature wire rating or a much larger aluminum wire, such as a 10 or 8 gauge, to power big equipment.

What Factors Affect Ampacity?

wire-for-30-amp

For better understanding of a wire’s ampacity rating, here are some factors affecting its current ratings.

1. Conductors Use in Wire

The first factor affecting wire ampacity is the type of conductors used in the wire. Typically, copper can hold more ampacity than aluminum, which is vital when using wires as extension cords.

2. Temperature Rating of the Wire

Generally, wires come at different temperature ratings, usually at 60, 75, or 90 degrees Celsius. As the heat capacity increases, so does the current rating.

3. Length of the Wire

Another factor affecting wire ampacity is the length of the wire. In simple words, as the length of the wire increases, its ampacity rating decreases due to voltage loss. Generally, voltage loss should not exceed 3%.

4. Loads Requirements

Each device has load requirements that a wire must also meet, especially during startup, when appliances may demand the highest current. When the ampacity of the wire does not match the rating of the device, it may heat up and cause a fire.

How Far can You Run 12-Gauge Wire?

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Depending on the current loads, a 12 gauge solid copper wire or even a stranded wire can run more than 150 feet. This is due to the scenario of voltage drops, where electricity declines in strength over more considerable distances.

Therefore, if you use the 12 gauge wire amp rating for 20 amps, you may only use it for 50 feet. With this distance, the chance of voltage drop is only 3.33 percent, and the cable will actually supply 20 amps to appliances.

If you lengthen the wire, it will only carry 15 amps at 100 feet and even less at 150 feet. In this case, your 20-amp device won’t receive enough power to run.

Can Amps Exceed 20 on 12 Gauge Wire?

Usually, a 12-gauge wire can handle 25 amps or even up to 30 amps if the temperature rating of the wire is up to 90 degrees Celsius. This means that the heat cables operate under determine their amperage.

However, if you need to run more than 20 amps, instead of utilizing a high-temperature wire, it is much safer to use the recommended wire for 30 amp, which is 10 gauge.

Conclusion

Knowing how many amps can 12 gauge wire handle is helpful, especially if you are working on a circuit installation. Once you put the wrong wire size in place, it can be the source of a bigger problem, such as voltage drops and fire.

Reading this article may help if you plan to work on a new circuit. However, call a professional for assistance if you still have difficulty sizing your cables.

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