I don't believe the 60% fill limit applies to sleeves, only short
sections of a complete conduit system. The way I think of sleeves,
they are not part of the electrical system. If the installation is
NEC-compliant without the sleeve, then the presence of the sleeve
doesn't change anything, it was just an aid in installing the cables.
On Mon, 1 Mar 2010 21:12:26 +0000 (UTC), Wayne Whitney
The real question is what your AHJ thinks. It says "nipples less than
24 inches", not conduit systems. In this jurisdiction that is what you
call a sleeve.
If this is a conduit system you can't exceed the fill in any of it.
Also there are plenty of AHJs who say if you pull wire in it, you need
to use a listed raceway. I have seen 4" white PVC pipes under
driveways failed because they pulled a 14/2 UF in it. Personally I
don't agree with that one.
It doesn't matter. If that was my AHJ I would be using RNC.
The attitude is that they make the appropriate raceway and that is
what you should be using.
Be careful to call these things ducts when you are talking to an
inspector since that is acknowledged in the code but not defined or
regulated. It might give you a better case.
As for sealing, find out if they want "draft stopping", "fire
blocking" or"Fire stopping" (3 different things). They would require
different materials for each.
Draft stopping could just be spray foam, Fire blocking might be as
simple as fiberglass insulation packed in the cavity or closely
fitting wood members but that is up to the opinion of your AHJ. Fire
stopping is a listed assembly of components with a fire resistance
rating based on time.
In the NEC 2008, Chapter 9 Table 1 gives the conduit fill allowances.
Note 2 says "Table 1 applies only to complete conduit or tubing
systems and is not intended to apply to sections of conduit or tubing
used to protect exposed wiring from physical damage." So it doesn't
apply to sleeves.
Note 4 says "(4) Where conduit or tubing nipples having a maximum
length not to exceed 600 mm (24 in.) are installed between boxes,
cabinets, and similar enclosures, the nipples shall be permitted to be
filled to 60 percent of their total cross-sectional area, . . ." So
this is relaxing the Table 1 requirements for certain parts of a
conduit system, it does not apply to sleeves.
Yes, it is completely illogical to say "this installation would be
compliant if that piece of PVC pipe weren't there, but now that it is,
it is in violation".
Well ain't that interesting.
IMHO it conflicts with 322.22 for PVC conduit (and xxx.22 for most other
"Cables shall be permitted to be installed where such use is not
prohibited by the respective cable articles. The number of cables shall
not exceed the allowable percentage fill specified in Table 1, Chapter 9"
============The 2002 NEC change proposal (for xxx.22) came from the code writing
panel and says very little about why the change was made. The
explanation is the change "clarifies that cables, where permitted
elsewhere in the code, are allowed to be used in a raceway." The
language was later changed to "where such use is not prohibited".
============ From the NFPA/IAEI code changes book:
Using raceways as isolated protective sleeves for cables was accepted in
It appears that the proposal may be for raceways that are connected to
the electrical system on one end. There are 2 examples shown.
One example is a box with a receptacle that has a conduit out the top
and has a Romex run through the conduit into the box. The top of the
conduit has a conversion fitting with a Romex connector.
[It is common practice to use essentially the same arrangement, without
the Romex connector, to protect exposed Romex.]
The other example is for one or more Romex runs into a panel through a
conduit as allowed in 312.5-C.
Seems like the application, as written, would be Table 1, Note 2 applies
in general but 322.22 applies specifically to all uses of PVC conduit.
But most raceways have an xxx.22 section, so I don't know what Note 2
applies to. Not likely that is what was intended.
If Table 1, Note 2 applies to all raceways that protect from physical
damage that leaves isolated raceways, as used in this thread, covered by
xxx.22 (which may or may not have been the intent).
This is unreasonable ambiguity. I guess the answer is ask the inspector.
For the "sleeve", it is not intended to protect from physical damage, so
fill restrictions apply via 322.22 to Chapter 9, Table 1. Heat is as
much a problem as full wiring systems.
Also wire ampacity derating applies, as you wrote long ago.
Well we are still reading "Note 2" differently. The first half of the
sentence already exempts all sleeves. The second half of the sentence
elaborates and gives a specific example but doesn't in any way limit
the first half. The upshot is that all sleeves are exempt.
Right, and that is handled by the derating requirements when bundling,
not by conduit fill. Conduit fill is for protection of conductors
from damage during installation.
I do read it different. IMHO Note 2 is taken as a whole and not split
into 2 sections. If the first half is independently applied, the second
half is not necessary.
Some of the other notes (5 and 9) are specifically for cable, which
would not likely be used in "complete conduit ... systems".
I figured out temperature was the wrong limitation right after I hit Send.
As you said, the point of Table 1 is to prevent damage to wiring at
installation. By your reading of Note 2, there is no limitation on the
number of cables that can be fished into a sleeve, and no protection
from installing too many cables. The limit that would protect a
"complete system" would not apply to a sleeve.
I see the second half of the sentence as only an elaboration and
explicit identification of the most common case of the first half. It
is like saying "Crash test regulations apply only to vehicles with 4
or more wheels and are not intended to apply to motorcycles." That
sentence means to me that crash test regulations do not apply to
vehicles with 3 wheels.
That's correct, but I don't see any problem with that. Cables have an
overall jacket that will help protect the conductor insulation from
damage. And a sleeve is likely to be a shorter run which would
require less pulling force than many "complete system" installations.
352 Rigid PVC conduit
"352.22 Number of conductors
Cables shall be permitted to be installed where such use is not
prohibited by the respective cable articles. The number of cables shall
not exceed the allowable percentage fill specified in Table 1, Chapter 9."
Identical language was added to most raceway articles (xxx.22) in the
2002NEC, probably to make existing practice clear. I would expect
inspectors would apply the same fill restrictions to PVC water pipe (if
they allowed water pipe). I haven't tried, but it would probably be
difficult to pull in Romex that did not comply with the fill restrictions.
The NEC doesn't specify a length or reason for using PVC conduit.
Fire stopping might actually be enforced by the building inspector (not
Well now I'm confused... :) At what point does does conduit become a full
"conduit system" that restricts NM cables in the conduit?
When I tried to decipher the code a couple years ago, I understood it to
mean "short" sections of conduit (i.e. 4 feet or less) where at least one
end was open for air flow was OK. Wouldn't a long "sleeve" of conduit (say
20 feet long from basement to attic) encounter the heat buildup the
restriction is trying to prevent?
I'm not trying to be sarcastic, I just don't understand what the deciding
factor is for NM cables in conduit. It would be good to know for future
When you want to use that conduit system for its normal purpose, to be
able to run individual electrical conductors like THHN, XHW, etc. In
that case, you have to count any NM cables also in the conduit towards
the conduit fill.
If you just have a sleeve or guideway for cables, like a piece of pipe
with open ends, then conduit fill does not apply, in my opinion. But
see my other post for the restrictions about supporting the NM cable.
BTW, there is obviously some variation in understanding about this
issue. So if you are planning to do this, you might want to check
with your inspector first. [If they say it is not allowed, you could
ask them what NEC article it violates.] You might find yourself in a
situation where your inspector disagrees and you decide it isn't worth
Conduit fill and derating are two different things. Conduit fill is
about avoiding damage to the conductors while installing them (cables
already have an outer sheath to help with that), while derating is
about keep the conductors from overheating when multiple conductors
are in close proximity.
BTW, you could have a derating issue due to bundling of cables without
any sleeve. E.g. if you drill a series of holes in a stud wall and
pack a bunch of cables tightly together through the holes (such as
more than 4 12/2 or 14/2 NM cables), that could be derating problem.
Certainly it would be if you also cable tied the cables together
in between the studs.
In fact, in the 2008 NEC, you have to derate any time you have more
than one cable going through a hole in framing that will be sealed
with thermal insulation, foam, or caulk. NEC 334.80 says, in part:
Where more than two NM cables containing two or more
current-carrying conductors are installed, without maintaining
spacing between the cables, through the same opening in wood framing
that is to be fire- or draft-stopped using thermal insulation,
caulk, or sealing foam, the allowable ampacity of each conductor
shall be adjusted in accordance with Table 310.15(B)(2)(a) and the
provisions of 310.15(A)(2), Exception, shall not apply.
So far, the only conduit related issue my inspectors have been concerned
with is bushings on the open ends of the conduit to prevent the conduit
from chafing the cables.
On a related note, I wonder how an open two story vertical run of conduit
would be viewed from a fire spread point of view? Our building inspectors
were strict about sealing all openings at floors and ceilings to prevent
fire spread. It seems like an uninterupted vertical run of conduit would
act a lot like a chimney, allowing a fire on the lower level a straight
path to the top floor (or attic).
I was surprised to learn on my last inspection that it was actually OK to
run two cables through the same clamp on the breaker panel. It may pass
inspection, but it didn't seem right to me. I prefer one cable per clamp.
Yes, that is a good idea, and in certain code sections is called out
I would expect it would be required to be fire caulked. My building
inspector required every penetration of top and bottom plates to be
fire caulked. Where I used EMT to sleeve NM cable for protection from
physical damage in a thin (2" framing) wall, I used bushings and
caulked the openings.
Are you talking about clamps that you installed in a KO on the panel?
The manufacturer's packaging or instructions should specify what
combinations of cables it is to be used with.
That seems like it would make future additions more difficult, having to
dig out the caulk before a new cable could be run. I wonder if a junction
box at the top and bottom would serve a similar function, but still allow
easy access in the future. Just thinking out loud...
Yeah, sorry for the vague description. I always use one clamp per cable in
the knock-outs, so it didn't even occur to me you could run more than one.
I was really surprised when the inspector said I could if I needed to.
Thanks for your response. I am not familiar with the term "Romex"
cables. The electric wire I run labeled as 12-2 NM-B With Ground. I do
not know if it is romex cable or not but it does not mention romex
anywhere on the packaging as far as I can see. But I will google romex
and see what I can find.
I have already purchased electrical conduit to run a 1 1/2 diameter
line from the basement for electrical and another 1 inch conduit for
I am going to have speakers at the other end of the room from the
computer and mixer so I think I will run conduit up the wall and over
the ceiling for those wires in case I want to change those someday.
And I will install two Cat5 data outlets. One on each end of the room.
I think I will run conduit for those lines too because data wire
requirements change so much.
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