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Thursday, July 15, 2021
Question:
Hello CQD,
If a nameplate on a motor has a value of 21 amperes, do I use that to size the conductors?
Skip Marshall
A
Answer:
Hi Skip,
Good Question. We will provide the response as a process to use for sizing conductors supplying motors. First, there is several bits of information missing from the questions. The answer is simply no, the tables in the back of Article 430 are used to determine the motor full load amperes, depending on the voltage, phase configuration, horsepower, etc. Once the current value is established from the applicable table in 430. Then Part II of Article 430 can be used to size the branch circuit conductors. What is helpful here is reading all of Section 430.6 which details this process and there is a great example (Example D8) of applying the NEC rules to motor installations in Annex D. Hope this is helpful.