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Monday, March 28, 2022
Question:
Hello Code Question of the Day.
Are the "Transformer Secondary Conductors" addressed in 240.21(C) tap conductors as defined in 240.2?
Palmer Hickman
A
Answer:
Hello Palmer,
Great to hear from you and thanks for the question. Your question is a bit broad as there are many transformer configurations. For this question and response, we will assume your question is related to the most common commercial secondary conductors including those supplied from 4-wire wye secondaries at 480/277, 208/120-volts, and 4-wire delta secondaries at 240/120. A Tap Conductor, as defined, is a conductor, other than a service conductor, that has overcurrent protection ahead of its point of supply that exceeds the value permitted for similar conductors that are protected as described elsewhere in 240.2. Based upon the definition, a service conductor is not a tap conductor. A conductor that is not protected in accordance with 240.4, is not protected at its rated ampacity and is a tap conductor. The first sentence in 240.4(F) Transformer Secondary Conductors provides answers to your question. It indicates that single-phase (other than 2-wire) and multiphase (other than delta-delta, 3-wire) transformer secondary conductors shall not be considered to be protected by the primary overcurrent protective device. Therefore, wye-connected secondary conductors are tap conductors with the tap starting at the secondary landing pads of the transformer.