Dịch vụ & Phân phốiCâu 115 / 521
A series-rated combination of overcurrent devices is permitted to protect equipment where the available fault current exceeds the interrupting rating of a downstream device, provided the combination is:
a.Any two breakers from different manufacturers
b.Field-assembled without documentation
c.Rated only by adding the two interrupting ratings
d.Tested and marked/listed as a recognized series combination, and the equipment is field-marked accordingly
Giải thích
Per 240.86, series ratings may be used only where the combination is listed and marked as a tested series combination (or engineered per 240.86(A)), and the end equipment is legibly field-marked to indicate the series-combination rating. Simply pairing arbitrary breakers or adding interrupting ratings is not permitted.
Trích dẫn luật: 2023 NEC §240.86Luyện miễn phí toàn bộ 521 câu hỏi — không cần đăng ký.
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