Electric Vehicle Infrastructure Training Program (EVITP) Practice Test

Ambient temperature directly influences how much current a conductor can safely carry because heat buildup from the current must be dissipated into the surroundings. In hotter environments, that heat dissipates more slowly, so the conductor’s insulation and temperature rise reach their limits sooner. The NEC provides adjustment factors that derate the base ampacity for ambient temperatures above 30°C, and these factors vary with the actual ambient temperature and the number of current-carrying conductors in a given installation. In EVSE design, this means you must select conductors with adequate insulation and a rating that, after applying the NEC adjustment factors, still meets the required charging current. Often this also involves choosing conductors with a higher temperature rating (such as 90°C insulation where permitted) and ensuring the protection devices and terminations are compatible with the derated ampacity. This approach ensures the system remains safe and within code across the expected temperature range.