SoonerEE
Member
- Location
- Edmond, OK
- Occupation
- Electrical Engineer
I am going through "Understanding the NEC Volume 1" and I'm not understanding the correction to one of the example problems. It is on page 192 and can be viewed at the link below.
https://www.mikeholt.com/documents/catalog/14_UNEC1_Textbook/14_UNEC1_Correx_Directory.pdf
I understand the correction from 12 to 10 AWG. It looks like there may have been a change in the example from 75c to 60c terminals. If the terminals of all the equipment were 75c, then would 12 AWG be sufficient (rated 25A at 75c)?
I don't fully understand why the answer was changed from 40A to 30A protection. Isn't the overcurrent protection for air conditioning and refrigeration equipment just supposed to match the name plate? I see that multiplying the rated-load current (18A) by 175% yields 31.5A, which would require a 30A OCPD (440.22(A)). Are you technically required to try the 30A OCPD before applying the 225% exception?
Despite the corrections indicated in the question, and the first bullet of the author's note, the Figure 240-10 and the second bullet point in the author's note still seem to be incorrect.
https://www.mikeholt.com/documents/catalog/14_UNEC1_Textbook/14_UNEC1_Correx_Directory.pdf
I understand the correction from 12 to 10 AWG. It looks like there may have been a change in the example from 75c to 60c terminals. If the terminals of all the equipment were 75c, then would 12 AWG be sufficient (rated 25A at 75c)?
I don't fully understand why the answer was changed from 40A to 30A protection. Isn't the overcurrent protection for air conditioning and refrigeration equipment just supposed to match the name plate? I see that multiplying the rated-load current (18A) by 175% yields 31.5A, which would require a 30A OCPD (440.22(A)). Are you technically required to try the 30A OCPD before applying the 225% exception?
Despite the corrections indicated in the question, and the first bullet of the author's note, the Figure 240-10 and the second bullet point in the author's note still seem to be incorrect.