Definition 376.22

[al hildenbrand]

How do u determine the size of the slice of bread?

Heh! It's very very thin.

 

[Carultch]

Otherwise, once you have a 31st wire in the gutter, you have to apply the 31% ampacity adjustment factor.

I mispoke. What I meant to say was:
Otherwise, once you have a 31st wire in the gutter, you have to apply the ampacity adjustment factor that corresponds to 31 wires.


I did think of another way to justify this for short lengths. If the length in question is less than 24 inches, you can neglect the ampacity adjustment factors as well. But once you reach the 25th inch, you have to apply them.

 

[infinity]

I did think of another way to justify this for short lengths. If the length in question is less than 24 inches, you can neglect the ampacity adjustment factors as well. But once you reach the 25th inch, you have to apply them.

Where does it say that?

 

[Carultch]

Where does it say that?

310.15(B)(2)(a) Exception No. 3: Derating factors shall not apply to conductors in nipples having a length not exceeding 600 mm (24 in.)


I know a wireway is not technically a nipple, but I understand that the physical environment and reason for derating is the same in either case.

 

[infinity]

310.15(B)(2)(a) Exception No. 3: Derating factors shall not apply to conductors in nipples having a length not exceeding 600 mm (24 in.)


I know a wireway is not technically a nipple, but I understand that the physical environment and reason for derating is the same in either case.

Just me but I see nothing in Article 376 that says the length of the wireway is applicable to the 30 CCC rule. The wireway could be 12" long but still requires the derating factors if any cross section in that 12" exceeds 30 CCC's.

 

[Carultch]

Just me but I see nothing in Article 376 that says the length of the wireway is applicable to the 30 CCC rule. The wireway could be 12" long but still requires the derating factors if any cross section in that 12" exceeds 30 CCC's.

So you are telling me that I can have 50 CCC's in a 12" length conduit nipple without derating per the rule I referenced above, but 50 CCC's in a 1 ft length wireway require derating? Simply because they are in a wireway instead of in a conduit?

 

[infinity]

So you are telling me that I can have 50 CCC's in a 12" length conduit nipple without derating per the rule I referenced above, but 50 CCC's in a 1 ft length wireway require derating? Simply because they are in a wireway instead of in a conduit?

Yup, unless I'm missing something there is no mention of length on the 30 CCC rule for wireways.

 

[Smart $]

310.15(B)(2)(a) Exception No. 3: Derating factors shall not apply to conductors in nipples having a length not exceeding 600 mm (24 in.)

I know a wireway is not technically a nipple, but I understand that the physical environment and reason for derating is the same in either case.

Ummm... I don't know what edition your on (or maybe your on something else :blink, but in the 2014 edition it's 310.15(B)(3)(a)(2)... Adjustment factors shall not apply to conductors in raceways having a length not exceeding 600 mm (24 in.).

Wireway is a raceway, but the 24" maximum is in reference to the length of the raceway.

 

[Smart $]

So basically I can't have more then 30 wires cross each other at any givin point in the gutter

Its not cross each other, but rather cross the plane of a cross section.

In your picture, look directly below the left side of the panelboard enclosure. That'd be the only cross sectional area in question. And don't forget, it's 30 current-carrying conductors, not just 30 circuit wires.

 

[infinity]

So you are telling me that I can have 50 CCC's in a 12" length conduit nipple without derating per the rule I referenced above, but 50 CCC's in a 1 ft length wireway require derating? Simply because they are in a wireway instead of in a conduit?

The elimination of raceways 24" or less as outlined in Chapter 9 only applies to raceways that are conduit or tubing. Silly I agree.

Chapter 9
Tables:
(4) Where conduit or tubing nipples having a maximum
length not to exceed 600 mm (24 in.) are installed be-
tween boxes, cabinets, and similar enclosures, the
nipples shall be permitted to be filled to 60 percent of
their total cross-sectional area, and 310.15(B)(3)(a) ad-
justment factors need not apply to this condition.