The total revision of Article 640 occurred in the 1999 NEC with the article more than doubling in size from the 1996 version. The newly reformatted article has incorporated new requirements for portable and fixed audio equipment.
Expansions cover audio signal generation, recording, audio processing, amplification, reproduction and distribution of the sound systems, public address systems, speech input systems, temporary audio system installations, electronic organs and other electronic musical systems.
The newly revised article provides specific references to audio-related systems in Part VI of Article 517 covering healthcare systems, such as nurse call systems and general sound systems. Public address systems and other similar audio sound systems have been added for assembly occupancies, as covered by Article 518.
Article 520 covers sound systems for theaters, audience areas of motion picture and television studios, performance areas and similar locations.
Audio installations for carnivals, circuses, fairs and similar events are covered under both permanent and temporary sound systems. Any audio recording, speech input systems and audio processing in motion picture, television studios and similar locations have been addressed in Article 640.
However, while this article covers most audio-related systems, it does not cover fire and burglary alarm devices or similar emergency audio systems.
When first determining the type of audio system to install in a particular occupancy, a meeting with the owner or user of the system should provide an understanding of the overall requirements of the system. This meeting will help achieve the results expected of the system.
The first thing to remember is that, based on Section 640.4, amplifiers, loudspeakers and other audio equipment must be located and protected against environmental exposure, or physical damage might result in fire, shock or personal hazard.
Certain types of audio equipment can carry substantial amounts of energy so that, when installed in a wet location, the system could expose a person or a pet to a shock hazard.
Compliance with 680.27(A) is a must for audio systems installed in or around pools with an emphasis on proper enclosures for the speakers, and specific wiring methods to ensure a low impedance path for bonding this equipment.
Section 640.10 does not permit audio equipment supplied by branch circuit power to be located laterally within 5 feet of the inside wall of a pool, spa, hot tub or fountain, and the branch circuit power must be protected by ground-fault circuit interruptor (GFCI) protection.
If installed adjacent to an artificial or natural body of water, such as a lake or a large manmade fountain, the audio system equipment supplied by branch circuit power must not be located laterally within 5 feet of the high water mark and again must be protected by GFCI protection.
For a permanent audio system installation, branch circuit power from the premises wiring system must be installed using any appropriate wiring in Chapter 3 based on the application and the location.
For example, in places of assembly, audio signal processing, amplification and audio reproduction equipment must be installed as fixed wiring methods, as covered in Article 640. Also, Section 640.25 requires loudspeakers installed in fire resistance-rated partitions, walls or ceilings to be either listed for that purpose, or installed in an enclosure or recessed area that maintains the fire-resistance rating.
Wiring between loudspeakers and amplifiers, between loudspeakers and loudspeakers, or as audio distribution for the audio equipment must comply with the requirements in Article 725 for Class 1, Class 2 or Class 3 circuits.
Where an amplifier is listed for a certain application, the amplifier should have marking on the equipment detailing the class of wiring method to use and ensuring the energy output is equivalent to the shock and fire risk of the same class as stated in Article 725.
Portable audio equipment must follow the same general rules as fixed equipment. However, cords and cables listed for portable use in accordance with Article 400 and 725 can be employed for the wiring between equipment, loudspeakers and amplifiers.
Portable equipment not listed for outdoor installations but used outdoors shall be permitted where appropriate protection from adverse weather conditions is provided to prevent shock or fire hazards.
Article 640 should be studied before attempting any audio system installation. EC
ODE is a staff engineering associate at Underwriters Laboratories Inc., in Research Triangle Park, N.C. He can be reached at 919.549.1726 or at firstname.lastname@example.org.