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Tuesday, July 11, 2017
Question:
My question is in regards to applying 220.5, when doing a calculation such as for article 440.22(a) if you have a R.L.A. of 17 amps and multiply by 175% you get 29.75 A. does 220.5 allow me to round up to 30 amps and use a 30 amp over current device. and would I be able to round up in the same manner in 430.52 exception 2 as well. Thank you.
Dean Lewis
A
Answer:
Hey Dean thanks for your question. Section 220.5 is for load calculations and 440.22 is for sizing the protective device for an individual motor compressor. The 29.75 value cannot be exceeded unless that size is not sufficient for the starting current of the motor then 225 % can be used as stated in 440.22(A). The manufactures values marked on the equipment cannot be exceeded either as stated in 440.22(C). For a motor load (not a hermetic refrigerant motor compressor) 430.52 (C)(1) Exception No 1 allows the next higher size to be used.