Mention firestopping and datacom
cabling in the same
paragraph to any cabling
professional and you will
typically see a smile disintegrate into a
grimace. Plugging the openings that will
frequently require cable changes just
seems to be counter-productive. While
deep down inside, everyone understands
the danger that fire presents, like any other
peril that can befall us, we tend to figure
that it’s something that happens to others
and will never happen to us. Actually the
odds are with you on that. The problem is
that like any other potentially dangerous
occurrence... it only takes one time.
Firestopping is indeed a frustrating experience
for most cable installation designers
and contractors alike. The code
requirements can be confusing and there
is a lot of misinformation that has been
passed down through the ages that only
serves to muddle the picture even more.
Let’s take a shot at examining what the
codes actually do say and see if we can
make this process a little easier to understand.
Along the way, we’ll try to provide
a few pointers that will help you design
and install cable through-penetrations that
are both functional and safe.
Raceway Systems
First, let’s discuss the method being
used to convey cables through the facility.
There are a lot of choices of course.
But for our purposes, we are going to simplify
things and focus on whether the cable
support method is continuous through
the fire barriers or whether it stops short of
them and only the cables themselves penetrate
the barrier.
Conduits: If cables are run inside continuous
conduits, the area around the conduit
must be firestopped where it
penetrates fire-rated barriers. Non-metallic
conduits will burn away during a fire and
may require more specialized firestopping
products.
Cable Trays: When it comes to cable
trays, there is a fair bit of misinformation
that has been perpetuated over time. You
may have heard that cable trays can’t penetrate
fire walls! This is patently false.
NEC 392.6 (G) states that Cable Trays are
permitted to extend through partitions and
walls or vertically through platforms and
floors in wet or dry locations where the
installations, complete with installed cables,
are made in accordance with the requirements
of 300.21 (which requires
these openings to be firestopped using approved
methods).
Cable trays can indeed make firestopping
more complicated and there are distinct
advantages to stopping the trays at
the barriers and using sleeves. Cable trays carry and consolidate
a high volume of cables. Effective
firestopping requires that you have enough
room for both the cables and the firestopping
where the cables penetrate fire barriers.
This means that cables will have to
be spread out more. Sleeves allow the cables
to be spread out into smaller bundles
that can be more easily and more effectively
firestopped.
Using Sleeves
Are sleeves required? I can’t find anything
in the codes that specifically requires
data and communication cable penetrations
to be sleeved. This is a good practice
for a variety of reasons and the codes
recognize that it is a common method.
Let’s discuss the use of sleeves more thoroughly.
How do the codes define sleeves? This
is very important. Understanding what the
codes consider to be the function of
sleeves will help us to better understand
just what is required and what isn’t. The
codes do not consider sleeves to be part
of the raceway system. Sleeves are best
defined in an exception to NEC 250.86
which refers to them as ...short sections
of metal enclosures or raceways used to
provide support or protection of cable assemblies
from physical damage shall not
be required to be electrically continuous.
Are sleeves required to be grounded?
We get into heated discussions on this
topic. But as you can see, NEC 250.86
referenced above also addresses this issue
and clearly indicates that while grounding
or bonding of the raceway system that
feeds the sleeve may be required, it is not
required for the sleeve itself.
Do the codes limit the amount of cable
that can be installed in sleeves? While
there are limits imposed upon raceway
systems, the codes do not place a limit on
the cable loading of sleeves. NEC Chapter
9, Table 1, Note 2 states that Table 1 applies
only to conduit or tubing systems
and is not intended to apply to sections of
conduit or tubing used to protect exposed
wiring from physical damage.
What about the need to install firestopping
within the sleeve? The use of
firestopping will generally require you to
limit the amount of cable installed in
sleeves. UL Classified firestop systems
published in the UL Fire Resistance directory
provide details on tested cable
types and fill ratios.
How about firestopping around the
sleeve? And do sleeves need to be attached
to the wall? I have bundled these two
questions because NEC 711.2 Installation
Details addresses both as follows... Where
sleeves are used, they shall be securely that cable penetrations require room for the existing cable
bundle, room for the anticipated growth of the cable bundle,
and room for the firestopping as well.
When our building was new, all of our cable penetrations
were compliant. Now 
many of them are completely
unsealed. What are we doing wrong? The problem we
see most often is the need to add cables is seldom anticipated.
Cables are added and in order to make room for
them, firestopping is removed. Over time all of the
firestopping will be removed. Unfortunately, cables will
be added wherever it is
easiest to add them. This
means that rather than install
a new sleeve, cables
will typically be added to
existing sleeves until no
more will fit.
The answer is to use
penetration designs that
make the best solution
the most attractive one
for the cable installer.
How do we do that? The
first step is to anticipate
additional cables and
provide plenty of spare
capacity. I always tell
people to think about
what they need right now
and triple it. My rationale
is that we always
underestimate the existing
requirement and we
are underestimating our
future needs as well. The
answer for providing
spare capacity is larger
sleeves as well as installing
spares. Making it
easy to add cables encourages
the installer to
do it right.
Another answer for the problem is to the use of newer
pathway products with built-in firestopping that can’t be
removed. These sleeves are always firestopped. Some
of these products permit 100 percent visual fill. So there
is no need for complicated NEC fill calculations. With
no firestopping to be removed, adjusted, or replaced...
these products allow cable installers to focus on what
they do best.
I hope that these suggestions and the code information
provided will make your cable firestopping experience a
little less painful going forward.
About the Author:
Jim Stahl is executive vice president,
Specified Technologies Inc.,
Somerville, NJ
