NEC 310.16 Table: Copper And Aluminum Wire Ampacity Chart (2024)

Whenever we need to need how many amps a wire can handle, we turn to the NEC 310.16 table. The 310.16 table is basically an ampacity chart; it tells us what is the ampacity of copper and aluminum wires. The full name for this table is “Table 310.16 Ampacities of Insulated Conductors with Not More Than Three Current-Carrying Conductors in Raceway, Cable, or Earth (Directly Buried)”.

Before we check the full 210.16 table found in National Electrical Code (NEC), let’s first look at why it is structured in the way it is. Namely, the current carrying capability of a wire – ampacity – depends on three key factors:

1. Size of the wire (expressed as AWG or kcmil). On the left side of the NEC 310.16 table (further on), we see different wire cross-sections (AWG or kcmil). The thicker the wire, the more amps it can carry. Wire ampacity increases with decreasing AWG number (Example: 12 AWG wire is thicker and can carry more amps than 14 AWG wire) and with increasing kcmil number (500 kcmil wire is thicker and can carry more current than 300 kcmil wire).
2. Type of metal wire is made out of (copper or aluminum). As we will see in the NEC ampacity chart, copper wires can handle more amps than same-size aluminum wires. That’s because copper has a lower resistivity (1.72 × 10^-8 Ohm×m at 68°F) than aluminum (2.65 × 10^-8 Ohm×m at 68°F). That means that the conductivity of copper is higher than the conductivity of aluminum.
3. Temperature. At higher temperatures, the conductivity of same-size same-type wire is higher. That’s why the NEC ampacity chart specifies the ampacity at 3 different temperatures; 60°C (140°F), 75°C (167°F), and 90°C (194°F). Temperatures also correspond to the type of wire (we will look at that and all the requirements for the NEC 310.16 table to hold true below the chart).

Understanding these three factors will help you understand and read the NEC ampacity chart. For clarity, we have divided this all-important 310.16 NEC table into two parts:

• 1st NEC 210.16 table includes copper wire ampacities from 18 AWG to 2000 kcmil for all 3 temperatures.
• 2nd NEC 210.16 table includes aluminum wire (or copper-clad aluminum wire) ampacities from 18 AWG to 2000 kcmil for all 3 temperatures.

Here is the 1st chart, followed by the 2nd chart.

NEC 210.16 Table For Copper Wire Ampacities (1st Chart)

For most household uses, you would use the 2nd ampacity column (ampacity at 75°C (167°F)). Here is the breakdown of copper wire types of specific temperature:

• 1st ampacity column at 60°C (140°F) temperature is relevant for TW and UF copper wires.
• 2nd ampacity column at 75°C (167°F) temperature is relevant for RHW, THHW, THW, THWN, XHHW, USE, and ZWcopper wires.
• 3rd ampacity column at 90°C (194°F) temperature is relevant for TBS, SA, SIS, FEP,FEPB, MI, RHH, RHW-2,THHN, THHW, THW-2,THWN-2, USE-2, XHH,XHHW, XHHW-2, and ZW-2copper wires.

Let’s have a look at the 2nd part of the NEC 210.16 table that specifies the ampacities for aluminum wires:

NEC 210.16 Table For Aluminum Wire Ampacities (2nd Chart)

Here is the breakdown by aluminum wire type:

• 1st ampacity column at 60°C (140°F) temperature is relevant for TW and UF aluminum wires.
• 2nd ampacity column at 75°C (167°F) temperature is relevant for RHW, THHW, THW, THWN, XHHW, and USEaluminum wires.
• 3rd ampacity column at 90°C (194°F) temperature is relevant for TBS, SA, SIS, THHN, THHW, THW-2, THWN-2, RHH, RHW-2, USE-2, XHH, XHHW, XHHW-2, and ZW-2aluminum wires.

Now, that we know all the copper and aluminum wire ampacities, let’s just cover the requirements and additional notes for the 210.16 table:

Requirements And Additional Notes

In order for the 210.16 to apply, these following 4 conditions need to be fulfilled:

1. Conductors must be used in 2000 volts or below circuits.
2. Conductor rating at the specified 3 temperatures must be observed.
3. When installing wiring in your house, the presumed temperature is the ambient temperature of 30°C (86°F).
4. The 210.16 table is applied to 1, 2, and 3 current-carrying conductors. If you have a 4 or 5 wire conductor, these ampacities do not apply.

With the complete NEC ampacity chart, we hope that now you have a good idea of how much current can any specified copper or aluminum wire handle. If you have any questions or suggestions, you can use the comment section below, and we will try to help you out.