30 ccc's

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SEO said:
For a better description of what I said look at the example in the 2005 handbook. If what you are saying is the case I wouldn't have to derate conductors in a wireway at all as long as it wasn't over 10 percent of the circuit length. I don't agree!:smile:
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Ok so what code article would you cite to say that 310.15(A)(2)exception does not apply to a wireway?
 
Derate for conductor fill required in Raceway?

Derate for conductor fill required in Raceway?

The 30 ccc?s are "electric light and power circuits", I assume?? Unless covered by table 210.2.
I assume 30amp snap switches, 200 amp main and neutral loads ??
This equates to 60 current carrying conductors?
My Method:
?equipment listed in Table 210.2 amend or supplement the provisions in this article and shall apply to branch circuits referred to therein.

300.17 Number and Size of Conductors in Raceway.
The number and size of conductors in any raceway shall not be more than will permit dissipation of the heat and ready installation or withdrawal of the conductors without damage to the conductors or to their insulation.

With or With out derate this limits you to fill. Then I look at Chapter 9, Table 1... conduit and tubing.. over 2/ 40% cM, #4, 24" no derate req.

Then I look for specifics for the raceway. IE 366.22, 376.22.. Number of Conductors....Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors.

My training says YES, Derate for "electric light and power circuits" that are not an integral part of a device or appliance. Look to 725.1 Scope. And the FPN . Then Look to 725.43? without applying the derating factors of 310.15 to the ampacity calculation?.
 
310.15 (A) (2)...It has nothing to do with derating for conductor fill.

310.15 (A) (2)...It has nothing to do with derating for conductor fill.

" 310.15 (A) (2) is intended to be used for circuits and feeders that pass thru different ambient tempertures."

True. For Derating:

310.15 (B) Tables. (2) Adjustment Factors. (a) More Than Three Current-Carrying Conductors in a Raceway or Cable.

Example: Table 400.5(A) Allowable Ampacity for Flexible Cords and Cables

# 10 STOW, Colum A = 25 AMPS 3 Current carrying

# 10 STOW, Colum A = 30 AMPS 2 Current carrying
 
SEO said:
Section 376.22 refers you to 310.15(B)(2)(a), 310.15(A)(2) is not referenced in section 376.22.
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Thats right because the NEC doesn't know all the componets of the system. If you had a 4' wireway full of condutors on a 30' run you would use 310.15(b)2. If the run was 40' or more then you could use 310.15(A)2.
 
where does it say its used for ambient temps.

where does it say its used for ambient temps.

As with some things in the code book, not a specific place, but implied.
310.15 Ampacities for Conductors Rated 0?2000 Volts gives
(A} General:
1) for Engineering supervision ... then look at 310.15(C) calculation with TA
for Tempreature Ambient.

and then..

(B) Tables for allowable ampacity... where all the tables have 'Based on Ambient Temperature of 30?C (86?F)' and 'CORRECTION FACTORS' for ambient at the bottom.

For me 'Ambient' has always been Implied, the same as the "Old" to "New" Table 110.20 has always been Implied.
Just my way of looking at it I guess:smile:
Always open to other views.
 
OPPS! Let me redirect that to 310.15 (A) 2
the Key is -Selection of Ampacity- Based on ...

(2) Selection of Ampacity. FPN refers to temperature limitations due to termination provisions. IE 60 or 75 ampacity selection.

My interpretation for the Exception is for the selection of the wire ampacity based on tempreture and the termination where wire ampacity is from 60 or 70 colum, then "..the higher ampacity shall be permitted to be used beyond the point of transition.." in the ambient Condition using the 90 colum for the wire only.

I may have a termination at a CB for #8 good for(60c) 40 amps, then when routed and corrected at the ceiling to (90c) 55 amps and terminating at my Equipment with a listed (75c) rating good for 50 amps.

Any Higher AMBIENT would there for need correction. My circuit has 3 Ampacity calculations, all based on Ambient. This adjustment is for varience in Temps as I was taught.

(2) Selection of Ampacity. Allows "adjacent portions of a circuit, the higher ampacity shall be permitted to be used beyond the point of transition"
using limits of 10' or 10% as the minimun beyond the transion point.
My enclosure has HVAC, but my raceway is outside the box, in 85f enviroment.

Does that cover my why of 310.15 (A) 2:-?
 
Pierre C Belarge said:
310.15(@)(A) is the general rule to follow. Article 376 is the specific requirement as per wireways.
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[NEC 2008 reference] 366.23(A) and 376.22(B) modify the implementation of 310.15(B)(2) ampacity derating for conductors in auxiliary gutters and wireways, respectively. These clauses do not modify 310.15(A)(2) Exception.

This stands to the reason that conductors in auxiliary gutters and wireways can comprise more than 10% or 10', whichever is less, of any one circuit.

One scenario to consider regarding 310.15(A)(2) Exception is that where the length of any one circuit conductor within the gutter/wireway exceeds the 10%/10' rule, the Exception becomes nonapplicable in that length of gutter/wireway.
 
Smart $ said:
[NEC 2008 reference] 366.23(A) and 376.22(B) modify the implementation of 310.15(B)(2) ampacity derating for conductors in auxiliary gutters and wireways, respectively. These clauses do not modify 310.15(A)(2) Exception.

This stands to the reason that conductors in auxiliary gutters and wireways can comprise more than 10% or 10', whichever is less, of any one circuit.

One scenario to consider regarding 310.15(A)(2) Exception is that where the length of any one circuit conductor within the gutter/wireway exceeds the 10%/10' rule, the Exception becomes nonapplicable in that length of gutter/wireway.
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The point here, IMO, is that when the trough is used as described in the OP, 310.15(A)(2)Ex gives some leeway in exceeding the 30 CCC rule with the 10%/10' stipulation. Now run that same trough as a raceway, say for 50' and the exception, rightfully, disappears.
 
infinity said:
The point here, IMO, is that when the trough is used as described in the OP, 310.15(A)(2)Ex gives some leeway in exceeding the 30 CCC rule with the 10%/10' stipulation. Now run that same trough as a raceway, say for 50' and the exception, rightfully, disappears.
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Not necessarily.

In many cases of utilizing gutter/wireway, circuits are branched out via raceway tie-ins (i.e. transitioned to conduit or such)... and as I stated earlier, the application of the exception is more dependent on the length of the circuit. If there is 10' circuit in the excepted group of CCC's, it would have to branch away from the group in the first one foot. A 20' circuit would have to branch away from the excepted group in the first two feet... and so on. Should all conductors be run as such, and there are 30 or less CCC at least 100' in circuit length remaining in the gutter/wireway after ten feet, the Exception is still applicable.
 
Smart $ said:
Not necessarily.

In many cases of utilizing gutter/wireway, circuits are branched out via raceway tie-ins (i.e. transitioned to conduit or such)... and as I stated earlier, the application of the exception is more dependent on the length of the circuit. If there is 10' circuit in the excepted group of CCC's, it would have to branch away from the group in the first one foot. A 20' circuit would have to branch away from the excepted group in the first two feet... and so on. Should all conductors be run as such, and there are 30 or less CCC at least 100' in circuit length remaining in the gutter/wireway after ten feet, the Exception is still applicable.
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I agree, but I did say 50' of trough exceeding the 30 CCC rule.
 
Section 376.22 states that the derating factors in 310.15(B)(2)(a) (shall )be applied where the number of current-carrying conductors exceeds 30. Section 310.15(A)(2) Exp. states that where two different ampacities apply to adjacent portions of a circuit, the higher ampacity (shall be permitted) to be used beyond the point of transition, a distance equal to 10' or 10 percent of the circuit length figured at the higher ampacity, whichever is less. Shall is a Mandatory Rule and shall be permitted is a Permissive Rule. A permissive rule does not override a mandatory rule so therfore section 310.15(A)(2) Exp does not apply for section 376.22.
 
SEO, what would be the difference between the two what ifs. In the first what if, I have a wireway that runs from one room into another room and then onto a third room. In the middle room i have more than 30 ccc's and should derate the conductors.
In the second what if, the wire way that is in the middle room has only 30 ccc's but the middle room is a boiler room with temps exceeding 30 degrees c.I should derate the conductors.
In both what ifs the wire way is over a 100' long, and the middle room is only 10' long. According to 310.15(a)2 i can disregard the temperature change and the derate change because the area of concern is less than 10% of the total run and not more than 10'.

Rick
 
SEO said:
A permissive rule does not override a mandatory rule so therfore section 310.15(A)(2) Exp does not apply for section 376.22.
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I would have to disagree. 310.15(A)(2)Ex applies to all derating, the same derating that's mandatory when you exceed 30 CCC's in a trough. Until the wording in 376 says that the exception doesn't apply, it does.
 
SEO said:
Section 376.22 states that the derating factors in 310.15(B)(2)(a) (shall )be applied where the number of current-carrying conductors exceeds 30. Section 310.15(A)(2) Exp. states that where two different ampacities apply to adjacent portions of a circuit, the higher ampacity (shall be permitted) to be used beyond the point of transition, a distance equal to 10' or 10 percent of the circuit length figured at the higher ampacity, whichever is less. Shall is a Mandatory Rule and shall be permitted is a Permissive Rule. A permissive rule does not override a mandatory rule so therfore section 310.15(A)(2) Exp does not apply for section 376.22.
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Apply the 376.22 modification of 310.15(B)(2)(a). You now have compliance. Now apply 310.15(A)(2) Exception. You still have compliance... as 310.15(A)(2) Exception and 310.15(B)(2)(a) are not dependent on each other.

There is nothing in Article 366 or 376 which renders 310.15(A)(2) Exception impermissible.
 
Look at the definition of Mandatory rules and Permissive rules in 90.5. I think that it's clear. However everyone has an opinon. How can a permissive rule override a Mandatory rule? Mandatory are required and permissive may be allowed but not required. How about section 310.15(B)(2)(a)?
 
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