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Join Paul Abernathy as he takes you through part 3 of the transformer series on how to size primary and secondary conductors to transformers and the all important use of the feeder tap rules to a transformer. Please watch Part 1 and Part 2 before you watch this video. This is based on the 2017 NEC.
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So if im taking a test i would do 250 percent time 90 (225) and size wire to 225 amp? For primary conductors?
Dan – Yes, if they ask for the maximum OCP for XFMR, assuming 250% if you do have primary and secondary protection given in the question you must meet 240.4 conductor protection rules.
The only time you dont have to meet 240.4 is when a feeder tap is supplying a XFMR then you have other rules in 240.21(B) you can follow but thats a different ball of wax I won’t try to teach in the comments.