Regarding 70V distributed sound systems, when is the wiring of such a system required to be in a raceway?
My interpretation, based on Article 725, is that if the amplifier output exceeds 100W, the wiring is classified as a Class 1 Remote-Control and Signaling Circuit it is required to be installed in a Chapter 3 wiring method. A1. The output wiring method for sound systems shall be as marked on the amplifier [640.9(C)], which is typically “Class 2 Wiring.” Class 2 wiring is not required to be installed in a raceway, but it must be installed in accordance with Article 725. However, Class 2 cables installed in air-handling spaces, such as above a suspended ceiling used for environmental air, shall be either plenum rated or they shall be installed in a metal raceway [725.61]. Q2. When can Electrical Nonmetallic Tubing (ENT) be stubbed out in a drop ceiling? The building in question is 3 stories and the ceiling in the hallway is regular T-bar. A2. ENT is permitted exposed in wall, floors and ceiling (including suspended ceilings) in buildings not exceeding three stories [362.10(1)(a) and 362.1
