Wire Size & Amp Ratings Ampacity is the maximum current that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. … Then, divide the total wattage by the voltage of the system, typically 120 or 240, and that will give you the required current or amps.

What does temp rating mean?

The temperature ratings of wire and cable products are key operating parameters. … It is usually defined as the maximum continuous temperature that the wire can withstand during its lifetime.

What are the three temperature ratings for conductor insulation on the ampacity table?

The two conductor types are each divided into three categories: 60°C (140°F), 75°C (167°F) and 90°C (194°F). Conductor sizes range from 18 AWG to 2,000 kcmil. Equivalent data for single-insulated conductors is found in Table 310.15(B)(17) (formerly Table 310.17).