Under 230.95, the rating of the service disconnecting means is considered to be the rating of the largest ___ that can be used.

• A. Fuse
• B. Circuit
• C. Wire
• D. All of these

Answer: (A)

The rating of the service disconnecting means is set by the maximum overcurrent device that could be installed on the service conductors ahead of the disconnect. In practice, that means the largest fuse that could be used to protect the service has the greatest influence on the disconnect’s rating. If the service could be protected by a certain fuse rating, the disconnect must be able to handle at least that current, so its rating is effectively tied to the largest fuse that could be used. This is why the correct answer points to a fuse. The wire size or circuit rating isn’t the limiting factor in this context, and using “all of these” isn’t appropriate because the rating isn’t defined by all of those elements together.