Q. With respect to a solar photovoltaic system, a disconnecting means is required to disconnect all current-carrying conductors of a photovoltaic power source from all other conductors in a building or other structure. A switch or circuit breaker shall not be installed in a grounded conductor unless ___________. Is a bolted or terminal disconnecting means (lug) acceptable as a disconnecting means for the grounded conductor?

A) you decide it’s okay / No

B) allowed by special permission of the Authority Having Jurisdiction / No

C) the switch or circuit breaker is part of a ground-fault detection system required by 690.5 — and that switch or circuit breaker is automatically opened and indicated as a normal function of the device in responding to ground faults / Yes

D) all conductors, including the grounded conductor, are simultaneously opened by a circuit breaker / No

Answer: C

Explanation: A change to 690.13 of the 2005 NEC makes it clear that you’re not allowed to install a switch or circuit breaker in the grounded conductor path. The conditions permitting a variation to this basic rule include the requirement that the switch or circuit breaker be part of a ground-fault detection system required by 690.5, and that this switch or circuit breaker is automatically opened and indicated as a normal function of the device in responding to ground faults.

Owen is the owner and president of National Code Seminars and the holder of master electrician certifications in 46 states. He can be reached at necexpert@aol.com.