- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I disagree. The round up is under any circumstances not just when all conductors are the same. Tables in Appendix C are only for conductors that are the same
NEC Ch.9 Table C.11 Error?
- Thread starter RookiEE
- Start date
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I take mistakes in the table personally.
I spent many hours re-working the tables in Appendix C because there was at least one error found. When I present NFPA with the error they decided to use the tables I made instead of the existing ones. The tables I did included all the conductors available, whereas the old table did not.
Every time someone says they found an error my heart stops. I figured I had screwed up. So far that hasn't been the case. I keep my fingers crossed. haha
There still may be some especially if the wire sizes in Table 5 are not correct.. I did not measure the wires.
I spent many hours re-working the tables in Appendix C because there was at least one error found. When I present NFPA with the error they decided to use the tables I made instead of the existing ones. The tables I did included all the conductors available, whereas the old table did not.
Every time someone says they found an error my heart stops. I figured I had screwed up. So far that hasn't been the case. I keep my fingers crossed. haha
There still may be some especially if the wire sizes in Table 5 are not correct.. I did not measure the wires.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
WOW you really checked every table? What code cycle did they adopt your tables?
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
2020 NEC Chapter 9 Table 1 Note 7 starts off "When calculating the maximum number of conductors or cables permitted in a conduit or tubing, all of the same size (total cross-sectional area including insulation), . . ." So the allowance only applies when all the conductors or cables are the same size.
Cheers, Wayne
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
It may have been the 2017. Before that I was at a meeting in Raleigh, NC and I brought it up to the CMP members that were there. They disagreed with me and said it was probably a rounding up problem. I insisted there was a problem, in fact, I sent in the question ahead of time with an example. He finally said to feel free to re-work the tables. His way of saying--bug off.
So I set up some crazy spreadsheets with some formulas that went on forever. Like the one below. Someone with more smarts than I could probably have simplified it. I created tables and heck I can't even remember what I did but it worked
=IF(VLOOKUP(C$9,EMT!$A$10:$N$25,14,FALSE)/VLOOKUP($B49,Table5NEC!$B49:$F49,5,FALSE)>=2.8,ROUND(VLOOKUP(C$9,EMT!$A$10:$N$25,14,FALSE)/VLOOKUP($B49,Table5NEC!$B49:$F49,5,FALSE)-0.3,0),IF(OR(VLOOKUP(C$9,EMT!$A$10:$N$25,12,FALSE)/VLOOKUP($B49,Table5NEC!$B49:$F49,5,FALSE)>=2.8,VLOOKUP(C$9,EMT!$A$10:$N$25,12,FALSE)/VLOOKUP($B49,Table5NEC!$B49:$F49,5,FALSE)>=1.8),2,IF(VLOOKUP(C$9,EMT!$A$10:$N$25,10,FALSE)/VLOOKUP($B49,Table5NEC!$B49:$F49,5,FALSE)>=0.8,1,0)))
After I did all the work I had the same problem.....damn
I figured the one common element was the wire thickness. And that was the issue they had transpose the insulation numbers, in one spot., for something like the and thwn. I don't remember the exact insulation type.
Anyway, I told them the issue and said if they wanted my tables here they are.... I didn't expect anything since I was past the deadline. I was surprised when I got the code book I say my tables.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I read right past that. Thanks