I am going to size a motor protection circuit breaker (MPCB) based on the NEC article 430 and what Mr. holt have said in ?5 motor calculations? video tutorial which is available in YouTube, but I have a problem in matching NEC rules with reality. For example for a 400V, 3 phase 4KW induction motor, SIEMENS suggests a MPCB with 10A rated current, 7 to 10A adjustable thermal overload current, and 130A as instantaneous short circuit or ground fault protection which is 13 times of the rated current of the MPCB. 130A for short circuit and ground fault protection is greater than the one given by NEC. So you are kindly requested to give me a description about this issue, if possible. Could you give an example for sizing and selection of a MPCB based on NEC rules, considering that short circuit protection of most MPCBs is fixed and in the order of 13 times of their rated current?
How to meet NEC requirements in MPCB sizing and selection?
- Thread starter rah1450
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- Chapel Hill, NC
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Could you tell us at what point in the video you are talking about-- hours and minutes....
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- Illinois
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- retired electrician
Can you give us the part number of the Siemens device?
yes. definitely. the part number 3RV1021-1JA1 size S0 motor protection circuit breaker.
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