In general, what is the minimum permitted rating of a service disconnect?
Answer: D, 60A.
Ok, I admit it, this week’s question was aimed at being a little tricky. The key to this question was in the first two words, “In general.” Section 230.79 requires that the rating of the service disconnect be not less than the calculated load to be carried, as determined by Article 220. In no case, however, can the rating be less than the applicable option given in 230.79(A-D). For instance, if the service supplies only a single branch circuit, the rating could be as low as 15A. If the service supplies not more than 2 two-wire branch circuits, it can be as low as a 30A. However, none of these conditions would be considered “in general.” Sections 230.79(A), (B), and (C) all require minimum ratings for specific installations. All other non-specific, or “in general”, installations shall not have a rating less than 60A.
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