Oklahoma Electrical Practice Exam

What is the ampacity of three #1 AWG THW copper wires in a raceway at an ambient temperature of 86° F?

1. 150 amps

2. 130 amps

3. 175 amps

4. 200 amps

The correct answer is: 130 amps

The concept of ampacity refers to the maximum amount of electrical current a conductor or group of conductors can carry before overheating. For #1 AWG THW copper wires, the ampacity can be influenced by several factors, including the number of conductors, the configuration of conductors in a raceway, and the ambient temperature. In general, the ampacity of #1 AWG THW copper wires at an ambient temperature of 86° F under normal conditions is approximately 130 amps. This is in line with the tables provided in the National Electrical Code (NEC) or similar standards, which give specific information based on various conditions affecting wire performance. When wires are placed in a raceway, temperature ratings may need to be adjusted, but for three conductors in a typical installation, the 130 amps figure remains applicable without necessitating additional derating for temperature or conductor grouping in many standard cases. Thus, 130 amps is accurately considered as the appropriate ampacity for this situation. This understanding of ampacity is essential for ensuring that electrical installations are safe, efficient, and capable of handling the expected load without risk of overheating or failure.