Question 6054 of 749 · Maryland Journeyperson Electrician Exam
What does the designation THHN indicate?
Exactly one answer is correct.
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Correct answer to question 6054
- B: Thermoplastic, high heat 90 C, nylon jacket, dry and damp locations
Explanation
THHN is a thermoplastic insulation rated 90 C for dry and damp locations with a nylon outer jacket. The double H means high heat resistance (90 C), and N means nylon. See Table 310.4(1) in NEC 2020 and 2023.
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