PVC Sweep Conductor Derate

[hill900505]

Hey everyone,
If I use a PVC sweep to bring direct burial underground conductors to an enclosure mounted on a post outdoor. Is this right code section I should refer to
" NEC 310.15.(B).(3).(a).(3) Adjustment factors shall not apply to underground conductors entering or leaving an outdoor trench if those conductors have physical protection,say, PVC, and if the number of conductors does not exceed four"
Does the number of conductors include the trench ground I am pulling into the enclosure as well?

Thanks!

 

[infinity]

Do you have more than 3 CCC's? Is the protection more than 10' long?

310.15(B)(3)(a)
(3) Adjustment factors shall not apply to underground
conductors entering or leaving an outdoor trench if those
conductors have physical protection in the form of rigid
metal conduit, intermediate metal conduit, rigid polyvinyl
chloride conduit (PVC), or reinforced thermosetting resin con-
duit (RTRC) having a length not exceeding 3.05 m (10 ft), and
if the number of conductors does not exceed four.

 

[hill900505]

Do you have more than 3 CCC's? Is the protection more than 10' long?

Yes, I have four CCCs and one EGC, the length of the sweep is less than 10 feet (it is a 36" radius sweep, so I guess the total length is probably 5 feet) Should I derate my conductor in this case? Not sure if EGC is counted as one conductor.

 

[infinity]

You need to derate for the 4 CCC's since you have 5 conductors. What are you feeding that gives you 4 CCC's?

 

[Smart $]

You need to derate for the 4 CCC's since you have 5 conductors. What are you feeding that gives you 4 CCC's?

310.15(B)(3)(a)(3) says adjustment does not apply to four or fewer conductors. An EGC does not count as a conductor for adjustment and correction requirements.

(3) Adjustment factors shall not apply to underground
conductors entering or leaving an outdoor trench if those
conductors have physical protection in the form of rigid
metal conduit, intermediate metal conduit, rigid polyvinyl
chloride conduit (PVC), or reinforced thermosetting resin conduit
(RTRC) having a length not exceeding 3.05 m (10 ft), and
if the number of conductors does not exceed four.

 

[infinity]

310.15(B)(3)(a)(3) says adjustment does not apply to four or fewer conductors. An EGC does not count as a conductor for adjustment and correction requirements.

I was thinking that too but I don't see where in that wording it excludes EGC's?

 

[Carultch]

I was thinking that too but I don't see where in that wording it excludes EGC's?

It seems strange to have a special exception to not apply derate factors for specifically 4 conductors, rather than to simply follow the standard ampacity adjustment table and its corresponding strategy of what conductors to count.

If this rule didn't exist, most if not all cases like this where you have 4 conductors (including the EGC) would not be derated anyway, since 4 = up to 3 + EGC. Maybe you could have RMC sleeveing with a direct burial bonding clamp below grade, and a bonding bushing above grade, no EGC inside, in which case 4 conductors does equal 4 CCC's. We know intuitively that the EGC does not carry current under normal operating circumstances, regardless if it is a wire or a raceway, and therefore would know that the EGC is not intended to be counted.

 

[Smart $]

I was thinking that too but I don't see where in that wording it excludes EGC's?

Title to 310.15(B)(3)(a) is "More Than Three Current-Carrying Conductors."

IMO "four conductors" in (3) thereunder implies at the very least circuit conductors, if not current-carrying conductors, but certainly not equipment-grounding conductors.

 

[Carultch]

Title to 310.15(B)(3)(a) is "More Than Three Current-Carrying Conductors." IMO "four conductors" in (3) thereunder implies at the very least circuit conductors, if not current-carrying conductors, but certainly not equipment-grounding conductors.

Well now it is conductors with a footnote, that specifies to count future use (spare) conductors and to only count the maximum conductors that can be simultaneously carrying current, so that switch travelers don't double count. The note needs to be what it says for this purpose, but the concept is still "current-carrying conductors".

 

[infinity]

Title to 310.15(B)(3)(a) is "More Than Three Current-Carrying Conductors."

IMO "four conductors" in (3) thereunder implies at the very least circuit conductors, if not current-carrying conductors, but certainly not equipment-grounding conductors.

I disagree, the exception say no more than 4 conductors and has been in the NEC since 1987. When it first appeared the table for derating was for conductors in a raceway, not CCC's. 4+EGC = 5 conductors so the exception cannot be applied. Don't ask me how they came up with 4 conductors. The original proposal called for 8' of raceway later changed to 10'. You can read the original proposal here:

Log # 1521
6- 113 : (Tables 310-16 through 310-19, Note 8,
Exception No. 5-(New)): Accept
Secretary's Note: The Correlating Committee directs
Panel 6 to correlate the action on this proposal with
the requirements of Section 300-5.
This action will be considered.by-the Panel as a
Public Comment.
SU~ITTER: Daniel W. VonBerg, Illinois Department of
Conservation
RECOMMENDATION: Add the below wording to the existing
Note 8:
"Exception No. 5: Derating Factors do not apply to
underground conductors entering, or leaving an outdoor
trench; if those conductors have mechanical protection
in the form of rigid metal conduit, intermediate metal
conduit or rigid nonmetallic conduit Schedule 80 having
a length not exceeding 8 feet (2.4.4 m) and the number
of conductors in a conduit does not exceed 4."
SUBSTANTIATION: Recreational areas, state parks, and
farm complexes have a large amount of underground
wiring entering and leaving outdoor trenches. Many of
these lines terminate in or loop through outdoor pole
or post mounted equipment and on the sides of out
buildings where cooling air abounds. Some of this
terminating equipment has limited conduit penetration
space making it difficult and/or unsightly to meet Note
8. The 8 foot limit allows for 2 foot in the ground
and 6 foot in the air. We have hundreds of existing
installations which meet this proposed exception and
over the years, have found no adverse affects due to
conduits longer than 24 inches and less than 8 feet in
length.
Although most of our underground lines are in
recreational vehicle parks and farm complexes, many are
not, and therefore a general exception is necessary.
PANEL ACTION: Accept.
VOTE ON PANEL ACTION: Unanimously Affirmative.

 

[Smart $]

I disagree, the exception say no more than 4 conductors and has been in the NEC since 1987. When it first appeared the table for derating was for conductors in a raceway, not CCC's. 4+EGC = 5 conductors so the exception cannot be applied. Don't ask me how they came up with 4 conductors. The original proposal called for 8' of raceway later changed to 10'. You can read the original proposal here:

Note 8 in the 1987 NEC was titled "Ampacity Adjustment Factors". and (a) thereunder was titled "More than Three conductors in a Raceway or Cable." I believe this was later clarified by changing it to current-carrying conductors (1993 NEC). It was not as if this was not intended all along. Additionally, we have never applied ampacity adjustment factors to EGC's and we have never counted them towards the number of conductors referred to in all of Article 310.

And when I say we, I mean all tradespeople that have implemented any section of Article 310. :happyyes:

 

[infinity]

I should have read further, maybe this covers it when we consider this to modify 310.15(B)(3)(a) and since (4) is part of the 310.15(B)(3)(a) provision.

310.15(B)(6) Grounding or Bonding Conductor. A grounding or
bonding conductor shall not be counted when applying the
provisions of 310.15(B)(3)(a).