NFPA flow chart

[Tulsa Electrician]

I ran across this file while looking for something and thought I would locate a link and share. There has been some discussion on ampacity adjustments.
Using the National Electrical Code®(NEC®) Ampacity ... https://www.nfpa.org/~/media/Files/Code or topic fact sheets/NECAmpacityWorkflow.pdf

 

[infinity]

I didn't peruse it but at a glance it does seem useful.

 

[wwhitney]

The flow chart takes the position that 310.14(A)(2) Exception (the 10%/10 feet rule) applies only to ampacity correction (for temperature) and not adjustment (for number of CCCs), which appears incorrect.

Cheers, Wayne

 

[ramsy]

The flow chart takes the position that 310.14(A)(2) Exception (the 10%/10 feet rule) applies only to ampacity correction (for temperature) and not adjustment (for number of CCCs), which appears incorrect.

Cheers, Wayne

The flow chart takes a conventional interpretation, literally by code statue, without supplemental-committee resolutions to public input.

For those who can convince AHJ's to consider code-panel interpretations, public input resolutions may be presented.

 

[ramsy]

The flow chart takes the position that 310.14(A)(2) Exception (the 10%/10 feet rule) applies only to ampacity correction (for temperature) and not adjustment (for number of CCCs), which appears incorrect.

Cheers, Wayne

Check out the public input resolution Don posted in this thread.

Where more than one ampacity applies

According to Jim Dollard, NEC code-making panel member. 2020 NFPA-70, 310.14(A)(2) Where more than one ampacity applies.. Exception: ..the higher ampacity shall be permitted.. applies only to the impact of ambient temperature.. "..cannot be applied to correction factors on rooftops or for...

forums.mikeholt.com

Then if you believe AHJ's will consider the supplemental publications, decide if you can convince AHJ's that wireway's also apply to conduit ?

 

[don_resqcapt19]

The flow chart takes a conventional interpretation, literally by code statue, without supplemental-committee resolutions to public input.

For those who can convince AHJ's to consider code-panel interpretations, public input resolutions may be presented.

I fail to understand how the language in the exception can be read as only applying to ampacity correction and not to ampacity adjustment.

Exception:
Where different ampacities apply to portions of a circuit, the higher ampacity shall be permitted to be used if the total portion(s) of the circuit with lower ampacity does not exceed the lesser of 3.0 m (10 ft) or 10 percent of the total circuit.

The defined term "ampacity" is the current that the conductor can carry under the conditions of use. Both the ambient temperature and the number of current carrying conductors are used to determine the conductor ampacity. With the use of the word ampacity in the exception, that automatically includes ampacity correction and ampacity adjustment.

 

[ramsy]

I fail to understand how the language in the exception can be read as only applying to ampacity correction and not to ampacity adjustment.

Yes I see unchanged code language with this exception, since before 1999 NEC 310-15(a)(2).

(A) General (Where Tables are used)
(2) Selection of Ampacity. ..Where more than one ampacity applies..

"Different ampacity" won't exclude CCC's, roof tops, or motor loads, within branches, feeders, or taps.

 

[ramsy]

that automatically includes ampacity correction and ampacity adjustment.

Your mileage may vary, if OP's NFPA flow chart, NFPA-70 Appendix-D Examples D3(a), Jim Dollard, and your AHJ persist in limiting this 10ft 10% exception to ambient, rather than CCC's, roof tops, or sections of motor loads.

 

[ramsy]

The flow chart .. ..appears incorrect.

Certainly is incomplete without considering continuous loads.
Especially deciding on continuous vs adjustments/correction factors, per 210.19(A)(1)(a) or (b)

 

[don_resqcapt19]

Your mileage may vary, if OP's NFPA flow chart, NFPA-70 Appendix-D Examples D3(a), Jim Dollard, and your AHJ persist in limiting this 10ft 10% exception to ambient, rather than CCC's, roof tops, or sections of motor loads.

Jim is an expert but his opinion is no more valid than any you find here. Also the things in Annex D are not enforceable code rules, just like informational note and the other Annexes. There is just nothing in the actual language that says what Jim says. but there was a group of people, including Jim that taught it that way.