Q. When installing a new service for a separate building constructed on the top floor of a parking garage, it has been determined that the service conductors will have to be installed in rigid metal conduit (RMC) starting in the vault below grade of the first floor level of the parking garage. The structural engineer and the general contractor will not permit the service raceway to be encased within the concrete of the structure. What are some options available to the electrical contractor to make this installation possible, while maintaining compliance with the 2005 NEC?
A) Install the RMC (containing service conductors), exposed from the vault to the first floor and up to the separate building on the top floor. Protection shall be provided where subject to potential severe physical damage.
B) Encase the RMC in concrete, not less than 2 inches thick, in a separate chase provided specifically for this conduit
C) Encase the RMC with brick, not less than 2 inches thick, in a separate brick chase provided specifically for this conduit.
D) If possible, install the service disconnect (for the separate building on the top floor) on the first floor in compliance with 230.70. From the first floor service disconnect location, install RMC, which will now contain feeder conductors to the separate building on the top floor. The conduit and feeder conductors will terminate in a disconnecting means that is installed per 225.32. This would permit the RMC to be exposed.
Answer: B, C or D
Explanation: Service conductors shall not be permitted to pass through one building or structure to provide service to another building or structure [230.3]. A raceway encased in at least 2 inches of concrete or brick is considered to be outside of the building or structure [230.6]. Service disconnect location shall comply with 230.70. Feeder disconnect location shall comply with 225.32.
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 [email protected].