Current Capacity
When choosing a wire for the job, the single most important factor is wire size. The International Code Council (ICC) published table 310.16 regulating the maximum performance current load for a given size and type of wire. Section 240.4 also discusses overcurrent protection for conductors 10 AWG and smaller. Likewise, International Electrotechnical Commission (IEC) Document 60228 specifies the technical parameters related to cable size.
You may click the links for the full tables, but the types typically found in a lab setting are listed below.
Copper Clad Aluminum, Type 60° TW/UF :
* Note that the ICC does not tabulate data for 20AWG and smaller, so aggregate and/or interpolated real-world values have been inserted.
** Note that the ICC does not tabulate continuous load data for 14 AWG and larger, so aggregate and/or interpolated real-world values have been inserted.
| American Wire Gauge | Circular Area (mm2) | Continuous Current | Peak Current |
|---|---|---|---|
| 24 | 0.25 | 2.0 Amps* | 3.5 Amps* |
| 22 | 0.34 | 3.5 Amps* | 5.0 Amps* |
| 20 | 0.50 | 4.25 Amps* | 6.0 Amps* |
| 18 | 0.75 | 5.6 Amps | 7.0 Amps |
| 16 | 1.50 | 8.0 Amps | 10.0 Amps |
| 14 | 2.50 | 10.0 Amps** | 12.0 Amps |
| 12 | 4.00 | 12.0 Amps** | 15.0 Amps |
| 10 | 6.00 | 18.0 Amps** | 25.0 Amps |
Material of the wire
Wire is typically made of three materials: Copper, Copper-Clad Aluminum, and Aluminum.
Aluminum is the cheapest while being the poorest conductor.
Copper-Clad Aluminum is typically a little more expensive, but conducts best.
Pure Copper is the best conductor, but has a weak tensile strength. This has to be taken into account for wires that might move, such as on a robot.
There are fourth and fifth types which typically only appear in high voltage power transmission: Aluminum-Clad Steel cable and Aluminum Conductor Steel Reinforced (ACSR). These utilize the conductivity values of aluminum wrapped around a central steel wire to support the weight between power poles.
Length of the wire
The length of a wire can be significant in a project due to voltage loss along the wire. Keep in mind that for most circuits, there are two losses which are additive: The positive and negative wires in DC and the Hot and Neutral wires in AC.
Using the data published under IEC 60228, the following examples may be presented:
| AWG | mm2 | Material | Ω/km | Wire Length | Resistance | Current | Voltage Drop |
|---|---|---|---|---|---|---|---|
| 18 | 0.75 | CCA | 26.7 | 1 Meter | 0.0267 Ω | 5 Amps | 0.1335 Volts |
| 18 | 0.75 | Pure Copper | 26.0 | 1 Meter | 0.0260 Ω | 5 Amps | 0.1300 Volts |
| 18 | 0.75 | CCA | 26.7 | 5 Meter | 0.1335 Ω | 5 Amps | 0.6675 Volts |
| 18 | 0.75 | Pure Copper | 26.0 | 5 Meter | 0.1300 Ω | 5 Amps | 0.6500 Volts |
| 14 | 2.5 | CCA | 8.21 | 1 Meter | 0.00821 Ω | 10 amps | 0.0821 Volts |
| 14 | 2.5 | Pure Copper | 7.98 | 1 Meter | 0.00798 Ω | 10 Amps | 0.0798 Volts |
| 14 | 2.5 | CCA | 8.21 | 5 Meter | 0.04105 Ω | 10 Amps | 0.4105 Volts |
| 14 | 2.5 | Pure Copper | 7.98 | 5 Meter | 0.0399 Ω | 10 Amps | 0.3990 Volts |
| 8 | 10.0 | Aluminum | 3.08 | 10 Meter | 0.0308 Ω | 20 amps | 0.616 Volts |
| 8 | 10.0 | CCA | 1.84 | 10 Meter | 0.0184 Ω | 20 Amps | 0.368 Volts |
| 8 | 10.0 | Pure Copper | 1.83 | 10 Meter | 0.0183 Ω | 20 Amps | 0.366 Volts |