- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I have gotten some inane comments like that also....
That is a good proposal and electrically it makes sense. But you said logical which unfortunately seems to escape much of the PI process.I made a PI for 2023 that would add the following sentence to the end of the note you quoted: "Where two or more conductors are protected by the same overcurrent device, and their currents are additive at the overcurrent device, they may be counted as a single conductor." Which seem logical to me, 20A spread over 5 conductors generates less heat than 20A on 1 conductor.
The panel response was "Loading and overcurrent protection could be changed in the future based on installed conductor sizes." To which my PC basically says "sure it could, but the possibility of future changes applies to any rule in the NEC, so give me a substantive technical reason to reject this particular proposal." I'm not holding my breath.
Cheers, Wayne
Actually, I see now that the proposed language is a bit unclear on the case of parallel conductors. So it should be "Where two or more conductors are individually protected by the same overcurrent device. . ."That is a good proposal and electrically it makes sense.
Ah, his is an issue has has come up in my work. I'm in the camp that says you can use as many conductors as will fit as long as they are on the same OCPD. After all, the physics of this are kind of obvious. As an inspector I've have no quarrels approving this. I do agree that the code language should be modified and have often thought of submitting a PI. I think wwhitney is on the right track.
Of course.you mean as many as the code allows for fill without derating, I assume. You still have to comply with conduit fill
I figured you knew but wanted to clarify to others reading this.Of course.
Well gee, I thought I had enough cred here that that would be assumed .I figured you knew but wanted to clarify to others reading this.
Yes it counts as 8. But the ungrounded supply and the neutral are the only two that possibly might need change in size after the adjustments.All in one raceway it counts as 8 CCC's. The fact that they're on one circuit is irrelevant. Something I've been complaining about for decades.
AFAIK the process as is isn't exactly precise to begin with when it comes to figuring actual potential for damage to conductors due to heating within a raceway/cable the results likely conservative enough you probably can get away with conductors that are improperly adjusted per the current rules and never really have any problems in most instances, especially if there is some load diversity that the code doesn't really address much at all. If everything is continuously loaded and especially at/near the base conductor ampacities, it maybe is good practice to assure you did follow what code does say for adjustments though.I made a PI for 2023 that would add the following sentence to the end of the note you quoted: "Where two or more conductors are protected by the same overcurrent device, and their currents are additive at the overcurrent device, they may be counted as a single conductor." Which seem logical to me, 20A spread over 5 conductors generates less heat than 20A on 1 conductor.
The panel response was "Loading and overcurrent protection could be changed in the future based on installed conductor sizes." To which my PC basically says "sure it could, but the possibility of future changes applies to any rule in the NEC, so give me a substantive technical reason to reject this particular proposal." I'm not holding my breath.
Cheers, Wayne
If there all on one circuit the adjusted ampacity for each conductor ( disregarding next size up rules) still needs to be greater than or equal to the OCPD size.Yes it counts as 8. But the ungrounded supply and the neutral are the only two that possibly might need change in size after the adjustments.
For example if feeding six 2 amp loads, the switched legs only draw 2 amps each but the common supply and common return both have 12 amps on them. The switched lines aren't even close to needing a change in conductor size compared to the two commons.
Yes, this example somewhat a poor one because if either a 15 or 20 amp circuit, only 8 conductors vs say 20 conductors, plus along with the small conductor OCPD rules you likely don't need to increase conductor size anyway.If there all on one circuit the adjusted ampacity for each conductor ( disregarding next size up rules) still needs to be greater than or equal to the OCPD size.