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Friday, July 31, 2020
Question:
Hello,
Is there a percentage maximum amount amperage a sub-panel can be off the main? An example would be a residence with a 100-amp main with a sub of 60, 70, or 80-amps. Thank you for your time.
Ray Jodoin
A
Answer:
Hi Ray,
Thanks for the question. The panelboard (sub panel as you call it) and associated feeder and service must be rated for the load served. The rating of the panelboard should be adequate and not exceeded. The calculations to determine the load on the feeder and service equipment and conductors are provided in Article 220 of the NEC.