Probable Effect Concentration Quotients (PECQS) Practice Test

What is the allowable ampacity of a 3.5 sq mm THWN copper conductor when directly buried?

1. 30 A

2. 25 A

3. 40 A

4. 15 A

The correct answer is: 25 A

The allowable ampacity of a conductor is influenced by factors such as the size of the conductor, insulation type, and installation conditions. In the case of a 3.5 sq mm THWN copper conductor buried directly in the ground, the current-carrying capacity must be aligned with the National Electrical Code (NEC) or relevant local codes. For a 3.5 sq mm THWN copper conductor, which is designed for wet locations and direct burial, the ampacity rating is determined by referencing the correct tables in the NEC or jurisdictional guidelines. Based on these standard tables, the ampacity value for a THWN copper conductor of this gauge typically lands in the range of 25 A when subjected to the conditions described (direct burial). This value takes into consideration the thermal characteristics of the conductor, the heat dissipation in the ground, and other factors that might influence its ability to carry current without overheating. The values you see in the options reflect standard ampere ratings based on such calculations. Understanding the context of these ampacity values is crucial for ensuring electrical systems operate safely and efficiently without risking overloads or overheating. The choice of 25 A accurately corresponds to the code specifications for this installation scenario.