We have an issue with temporary power for a large project on an existing campus. The temporary consists of a 15-kilovolt (kV) feeder from the existing campus, supplying a transformer to step down to 480/277 volts (V). We had specified a 1,600-ampere (A), 480/277V main disconnect with overcurrent protection that would supply a switchboard. The installer supplied the switchboard directly from the secondary terminals of the transformer. An engineer with the electrical contractor informed us that NEC table 450.3(A) Note 2 permits six individual circuit breakers with an ampacity more than 250 percent of the full load amperes for transformer secondary protection. He also told us this installation complies with 240.21(C)(6) because it is shorter than 25 feet and that sections 215.10 and 230.95 do not apply because there are no disconnects rated at 1,000A or more. We disagree. Can you tell us what is required?
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