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Friday, April 28, 2017
Question:
Good Morning, What is the history behind the small conductor rules of 240.4(D), specifically (3) and (5) & (7). If equipment terminations are rated for 75 degrees C why are the conductors still limited to the 60 degree column?
Pat Lyon
A
Answer:
Hey Pat thanks for your question. It is my understanding that when ampacity values were increased many years ago because of the change in insulation types the code making panel kept the overcurrent protection values for those conductor sizes based on their 60 degree C values as a safety factor. Their use for general purpose branch circuits were likely to be misused.