I would not suggest running romex in conduit. You can buy reels of THHN
seperatley, ie black, white, green on seperate reels. This is the way
commercial jobs are wired. 2 inch EMT will fit 15 circuits easily.
The Old Bear wrote:
We're working on a kitchen renovation in a house built about
1900. The kitchen space has been gutted down to the studs
and overhead joists and is nice and easy to wire with romex.
There are sufficient kitchen circuits to warrant a new
sub-panel which will be located in the basement just
below the kitchen. The basement has a plaster ceiling.
The question is how to handle the penetrations through the
plaster ceiling and into the wall cavity above while
maintaining a proper fire-stop.
At the main panel on the opposite side of the basement,
the existing branch circuits run in romex going right into
the ceiling and plastered right up to the romex. There
is also older BX armored cable. I am comfortable with
plastering around BX, but romex seems to be a different
animal.
One way I can handle the penetration(s) up from the new
sub-panel is with a short length of 2-inch conduit passing
from the sub-panel through the ceiling and into the wall
cavity above. A bushing would be used on the end of the
conduit and the romex would be run in the conduit from
the sub-panel and then fan out to the various outlets,
switches and fixtures.
There are about 15 branch circuits for the kitchen and
the question is how many 12/2 and 14/2 romex will fit into
a 2-inch conduit and still comply with the NEC conduit
fill limitations and not be so tightly packed as to require
de-rating. I can do the calculation for individual #12
and #14 conductors but I don't know how to figure in the
romex's outer jacket. And I seem to recall that the jacket
on NM-B romex is rated at 60-degrees C even though the
indivual conductors are rated at 90-degress C.
(Could the romex jacket be removed where it enters the
conduit and just the inner conductors and ground run through
the conduit and into the sub-panel if necessary?)
Suggestions on how to handle the floor penetration(s) for
so many circuits while maintaining a proper fire-stop would
be appreciated. Thanks.
Bear
See NEC Chapt 9 Tables:
Here are some notes:
"(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, and 310.15(B)(2)(a) adjustment
factors need not apply to this condition.
(5) For conductors not included in Chapter 9, such as multiconductor
cables, the actual dimensions shall be used.
(6) For combinations of conductors of different sizes, use
Table 5 and Table 5A for dimensions of conductors and
Table 4 for the applicable conduit or tubing dimensions.
(7) When calculating the maximum number of conductors
permitted in a conduit or tubing, all of the same size
(total cross-sectional area including insulation), the
next higher whole number shall be used to determine
the maximum number of conductors permitted when
the calculation results in a decimal of 0.8 or larger.
(8) Where bare conductors are permitted by other sections
of this Code, the dimensions for bare conductors in
Table 8 shall be permitted.
(9) A multiconductor cable of two or more conductors
shall be treated as a single conductor for calculating
percentage conduit fill area. For cables that have elliptical
cross sections, the cross-sectional area calculation
shall be based on using the major diameter of the ellipse
as a circle diameter."
And don't forget the derating.
Do not use romex in conduit! Use single conductor stranded wire. The
only way I would even use solid wire in a conduit is if it came with
the conduit like armored cable (but even them sometimes I buy the plain
armor and run stranded wire through it.
That is exactly correct. The conduit is just to handle
the distance from the top of the sub-panel to the bottom of
the partition above.
The objective is to manage the floor penetration with
easier fire-stopping than drilling a dozen 5/8" holes in
close proximity to one another and filling around the romex
with caulk or rock wool.
The reason that I cannot use single conductor wire is that
I would need to splice it to the romex running around the
kitchen -- which would require a box and there is no way to
make such a box accessible because it would be behind the
base cabinets.
[Thanks to all who responded. The code citation for using the
actual dimension of the romex was very helpful.]
Yes, that's what I thought....
I've seen a website somewhere that gives the cross sectional area of Romex, but
it should
be close enough to use width X thickness if you're concerned about the fill
percentage...
OH FUCK! Use fire caulk and forget the nipple. You are trying to engineer
a disaster. If nothing else ask your local AHJ about what is acceptable.
We're working on a kitchen renovation in a house built about
1900. The kitchen space has been gutted down to the studs
and overhead joists and is nice and easy to wire with romex.
There are sufficient kitchen circuits to warrant a new
sub-panel which will be located in the basement just
below the kitchen. The basement has a plaster ceiling.
The question is how to handle the penetrations through the
plaster ceiling and into the wall cavity above while
maintaining a proper fire-stop.
At the main panel on the opposite side of the basement,
the existing branch circuits run in romex going right into
the ceiling and plastered right up to the romex. There
is also older BX armored cable. I am comfortable with
plastering around BX, but romex seems to be a different
animal.
One way I can handle the penetration(s) up from the new
sub-panel is with a short length of 2-inch conduit passing
from the sub-panel through the ceiling and into the wall
cavity above. A bushing would be used on the end of the
conduit and the romex would be run in the conduit from
the sub-panel and then fan out to the various outlets,
switches and fixtures.
There are about 15 branch circuits for the kitchen and
the question is how many 12/2 and 14/2 romex will fit into
a 2-inch conduit and still comply with the NEC conduit
fill limitations and not be so tightly packed as to require
de-rating. I can do the calculation for individual #12
and #14 conductors but I don't know how to figure in the
romex's outer jacket. And I seem to recall that the jacket
on NM-B romex is rated at 60-degrees C even though the
indivual conductors are rated at 90-degress C.
(Could the romex jacket be removed where it enters the
conduit and just the inner conductors and ground run through
the conduit and into the sub-panel if necessary?)
Suggestions on how to handle the floor penetration(s) for
so many circuits while maintaining a proper fire-stop would
be appreciated. Thanks.
Bear
Some Jurisdictions don't allow "stacks" coming out of panels as you
describe.
In that case you may want to consider running 4 - 3/4" conduits from
the panel to 4 boxes where outlet or devices will be. That will handle
16 circuits easily while drilling only 4 - 1 1/8" holes. Use 4 11/16"
x 2 1/8" deep boxes with P rings and run 4 circuits in each conduit,
then take 4 circuits out of each box with Romex. Box fill will be
within allowed limits and conductor derating will not be a problem.
This is the rule 312.5(C)Exception: Cables with entirely nonmetallic
sheaths shall be permitted to enter the top of a surface-mounted
enclosure through one or more nonflexible raceways not less than 450
mm (18 in.) or more than 3.0 m (10 ft) in length, provided all the
following conditions are met:
(a) Each cable is fastened within 300 mm (12 in.), measured along
the sheath, of the outer end of the raceway.
(b) The raceway extends directly above the enclosure and does not
penetrate a structural ceiling.
(c) A fitting is provided on each end of the raceway to protect
the cable(s) from abrasion and the fittings remain accessible after
installation.
(d) The raceway is sealed or plugged at the outer end using
approved means so as to prevent access to the enclosure through the
raceway.
(e) The cable sheath is continuous through the raceway and extends
into the enclosure beyond the fitting not less than 6 mm (1/4 in.).
(f) The raceway is fastened at its outer end and at other points
in accordance with the applicable article.
(g) Where installed as conduit or tubing, the allowable cable fill
does not exceed that permitted for complete conduit or tubing systems
by Table 1 of Chapter 9 of this Code and all applicable notes thereto.
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