Wire derating questions

R

Rayliu999

Member
Location
San Jose CA
Occupation
Electrician
John Guys, I just had an inspection, and the inspector told me to derating my wire because my entire race way is over 24”
My understanding is that I have one 12” conduit from panel#1 running into a gutter and have another 12” conduit from gutter to panel#2, and the total CCC is 24 counts, I should be ok with the “shout conduit rule”, am i right? Or as the inspector says, the total raceway is over the limits?
Thanks
 
(a) More than Three Current-Carrying Conductors. Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed in raceways, the allowable ampacity of

Ask you inspector to look up the meaning of continuous.
 
Strathead said:
(a) More than Three Current-Carrying Conductors. Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed in raceways, the allowable ampacity of

Ask you inspector to look up the meaning of continuous.
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Thanks a lot man, I wish they understand the rules like you
 
You could have a 24" raceway to a box then another 24" raceway to another box and not derating would apply. Once you break the continuous raceway with the box you do not add the length of the short sections of raceway together.
 
infinity said:
You could have a 24" raceway to a box then another 24" raceway to another box and not derating would apply. Once you break the continuous raceway with the box you do not add the length of the short sections of raceway together.
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He is considering the gutter to be a part of the raceway which is not right, am I correct?
 
The commas in that section throw me off. I wonder if he reads it the same way.

"The ampacity of each conductor shall be reduced as shown in Table 310.15(C)(1) where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables not installed in raceways are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.). "

I read it as if any of the two apply,

1) more than 3 CCCs in a raceway
2) single conductor or multiconductor cables (not in raceway) are installed without maintained spacing (undefined term) for a continuous length longer than 24in.

I don't see the conduit having the 24in requirement. It shows up again in (b) but that is applied to the conductor being less than 24in.

So in my mind, so long as there are more than 3 CCCs in any conduit and the CCCs length is over 24in then the adjustment might be required.

Arguably kind of silly with small lengths of conduit. And adjustment might only impact the conductor for a given length and not the whole run, but still. You also have 310.14(A)(2) exception. It would cover portions of the circuit with a lower ampacity.
 
Elect117 said:
So in my mind, so long as there are more than 3 CCCs in any conduit and the CCCs length is over 24in then the adjustment might be required.
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The text quoted in post #2 from 2023 NEC 310.15(C)(1) could certainly be clearer, and the 2026 NEC cleans it up.

However, 2023 NEC 310.15(C)(1)(b) has the text quoted in post #8, so that modifies the base text of 310.15(C)(1).

Cheers, Wayne
 
wwhitney said:
The text quoted in post #2 from 2023 NEC 310.15(C)(1) could certainly be clearer, and the 2026 NEC cleans it up.

However, 2023 NEC 310.15(C)(1)(b) has the text quoted in post #8, so that modifies the base text of 310.15(C)(1).

Cheers, Wayne
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I see what you are saying. The verbiage threw me off.
 
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