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Monday, September 26, 2016
Question:
Hello,
Please explain what the NEC demand factors are and how to apply them to reduce the expected load when calculating panelboard loads. The factors I have found are in 220.42, 220.43, 220.44, 220.50, 220.51, 220.60, and 220.61. I have seen some forums where 215.3 is also mentioned as a demand factor. Are there any other demand factors besides these?
Thanks.
Pathros Cardenas
A
Answer:
Hey Pathros thanks for your question. The term Demand Factor is defined in Article 100 and applying them essentially results in the portion of the total connected load that is expected to be operated at any given time. You skipped some other demand factors such as 220.53 for dwellings so I think your focus is for other than dwelling units. Section 215.3 is not a demand factor but is a minimum rating of overcurrent protection based on whether the load is continuous or noncontinuous. There are other rules that can apply and Table 220.3 provides additional load calculation references. For example 670.4(A) allows a duty cycle to be applied to the supply conductors to industrial machinery. Identify the equipment being supplied in your application and determine if there are any specific rules for that type of equipment then apply the demand factors in Article 200.