NEC Annex B
- Thread starter stanrat
- Start date
- Status
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
stanrat said:
Mike doesn't live here. Only us rug rats do. Annex B is only allowed to be used under engineering supervision and is not part of the NEC requirements. Under certain conditions engineers may be allowed to use these values-- I guess.
- Location
- Illinois
- Occupation
- retired electrician
If you are doing an installation that uses the Article 220 load calculations, then the use of 310.16 is fine for the conductor ampacity. If the load calculations are real, then you will burn the conductors up if you use 310.16 for an underground duct bank of any size.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Take a look at the top of that table. It restricts its own use to a particular set of installation configurations. An underground ductbank that has three current-carrying conductors in close proximity to three others, and in close proximity to another three, and a bunch of others, may not, in the opinion of some, fit within the constraints of the table. I agree with Don's interpretation of when it can or can't be used for an underground ductbank. I also agree with Dennis's statement about the annex being the purview of engineers.stanrat said:
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