It's unfortunate, but the sizing of feeders, transformers, and related switchgear for a permanent dimmer-per-circuit system is an area where confusion and misinformation are too often the norm. This confusion is so pervasive that in 1993 the National Electrical Code was modified to help clear up the mess. It's an interesting anecdote. In 1990 the United States Institute for Theatre Technology (USITT) proposed a change to NEC Article 520, Theatres and Similar Locations, to clarify the feeder ...

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