Dịch vụ & Phân phốiCâu 49 / 521
Conductors are connected to a transformer secondary without an OCPD at the secondary terminals. What set of rules governs their length and sizing?
a.The small-conductor rule 240.4(D)
b.The service-entrance rules of Article 230
c.There are no restrictions
d.The transformer secondary/tap rules of 240.21(C)
Giải thích
Per 240.21(C), transformer secondary conductors without secondary protection must follow specific tap rules limiting length (e.g., 10 ft or 25 ft) and minimum ampacity. Article 230 covers services, and 240.4(D) covers small conductors; unrestricted runs are never permitted.
Trích dẫn luật: 2023 NEC §240.21(C)Luyện miễn phí toàn bộ 521 câu hỏi — không cần đăng ký.
Câu hỏi liên quan cùng chủ đề
- What is the full-load primary current of a 75 kVA, 3-phase, 480 V transformer?
- For a transformer over 1000 V or with primary-only protection under 450.3(B), where primary current is 9 A or more, the primary OCPD generally may not exceed what percentage of primary full-load current?
- A transformer has a primary full-load current of 40 A and uses primary-only overcurrent protection. What is the maximum standard primary OCPD (125% rule)?
- Why must ventilating openings of a dry-type transformer be kept clear of walls and obstructions?
- For a single service, what is the maximum number of service disconnecting means permitted (for one set of service-entrance conductors)?
- As a general rule, how must a panelboard be protected against overcurrent?
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