Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multi conductor cables are stacked or bundled longer than 24 inches without maintaining spacing and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in the following table:
*Refer to 310.15(B)(2) for the ampacity correction factors where the ambient temperature is other than 30°C (86°F). **Refer to 240.4(D) for conductor overcurrent protection limitations.
Wire Size Chart and Maximum Amp Ratings - Wire Size Calculator
The wire size chart below shows allowable ampacities of insulated conductors rated up to and including 2000 Volts, 60°C through 90°C (140°F through 194°F), not more than three current-carrying conductors in raceway, cable, or earth (directly buried), based on ambient air temperature of 30°C (86°F).
American Wire Gauge “AWG” Chart – Wire Size & Ampacity Table
The following AWG “American Wire Gauge” table shows the AWG Size and diameter in millimeter “mm” and inches in “in”, its cross sectional area in mm2, Inche2 and kcmil or MCM and resistance in ohms per 1000 feet and 1000 meter.
NEC 310.12 Table: Wire Sizes For 100-400 Amp Services (83% Rule)
This table tells you what gauge wire (AWG or kcmil) you need to use for services and feeders ranging from 100 amps to 400 amps current. It gives us the AWG or kcmil number for copper and aluminum wires (same as copper-clad aluminum wires).
Most aluminum building wire in Types THW, THHW, THWN/THHN, and XHHW conductors is compact stranded. Table 5A provides appropriate dimensions for these types of wire.
Conductor Ampacity Based on the 2017 National Electrical Code
Ampacity based on NEC ® Table 310.15 (B) (16) (formerly Table 310.16) Allowable Ampacities of Insulated Conductors Rated Up to and Including 2000 Volts, 60° through 90°C (140° through 194°F), Not More Than Three Current-Carrying Conductors in Raceway, Cable, or Earth (Directly Buried), Based on Ambient Temperature of 30°C (86°F).
These three NEC rules required the overcurrent protection device (breaker or fuse) be sized no less than 100% of the noncontinuous load, plus 125% of the continuous load. Section 240-6(a) contains the list of standard size overcurrent protection devices.
NEC 310.16 Table: Copper And Aluminum Wire Ampacity Chart
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.
Allowable ampacities of single insulated conductors Rated 0 - 2000 Volts, in free air, based on ambient air temperature of 30°C (86°F). For ambient temperature other than 30°C (86°F), multiply the allowable ampacities specified above by the appropriate correction factor shown below.