- Installing UTP Cabling
UTP
Cabling can be installed in many ways, under floors or above ceilings
in cable trays, inside conduit, in J-hooks attached to walls or roof
supports, inside walls, even inside special cable trays in modular
furniture. Installations need to be tailored to the property being
cabled, the equipment being connected and local building codes, making
generalizations about installations difficult. For all installations,
however, certain cautions apply.
 
 
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- Mistakes
in installation of UTP cable can be detrimental to cabling performance
and very difficult to detect. A mistake that could keep the entire
system from working might not show up at all until the system is
completely installed and turned on.
- Proper
installation depends on
proper design. The facility in which cabling is being installed should
be designed according to industry standards which include all the
pathways and spaces in which cabing and equipment will be installed.
Even where the cables are routed in the building is important. Cables
should be kept dry and in moderate temperatures. Above the ceiling in
some buildings in hot climates can get very hot, causing UTP cable to
have higher attenuation so it will not support full standard link
distances.
- Supports
for the cables should be wide enough to support the cables without
distortion, spaced closs enough so the weight of cable supported
(copper cable bundles are heavy!) and have no sharp edges to cut or
kink the cables.
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- The performance of the cabling
network is also heavily dependent on the installation. The components
used in structured cabling installation have been carefully designed
and exhaustively tested to meet or exceed the requirements of
EIA/TIA 568 for performance at 100-250 MHz. If the cable is not
properly installed, performance will be degraded.
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- Just
like we keep reminding about maintaining the pair twists right down to
the terminations, there are other things you must realize to maintain
the performance of Cat 5e/6/6a UTP cable! First of all, pulling tension
must be less than 25 pounds. That's not very much tension! Pulling at higher
tension can stretch the cable and affect the twists in the pairs, and
it's those twists that make the cable perform well at high frequencies.
- Puling
cable in conduit is especially critical as you must deal with friction
in the conduit and pulling around bends. Installing breakout boxes for
intermediate pulls is often necessary and one may need to use pulling
lubricants in the conduit. (Just be sure to use an appropriate
lubricant to prevent long term degradation of the cable.)
Likewise, kinking the cable by letting it get twisted or pulled around
sharp corners can cause permanent damage. Damaged cable will probably
not pass crosstalk tests.
Patch
panels can have massive number of cables, so managing these cables can
be quite a task in itself. It is important to keep all cables neatly
bundled and labeled so they can be moved when necessary. However, it is
also important to maintain the integrity of the cables, preventing
kinking or bending in too small a radius which may adversely affect
frequency performance.
One
should also avoid bundling the cables too tightly. Crushing the cables
can affect the performance, since it can affect the twist and pair
alignment in the cable which affects high frequency performance. If one
uses regular plastic cable ties, they should be tightened only finger
tight and cut off - do not use cable tie guns which may tighten tight
enough to damage the cables. Preferably use "hook and loop" cable ties
(shown above) which have an added advantage that they can easily be
opened to add or remove cables. 
- Most cable boxes are designed
to allow easy pulling directly from the box. Gather up several
boxes and pull a bunch of cables at once. Tape them together
and attach a pullstring or just feed them along by hand.
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- You
can pull from the telecom closet or to the closet, whichever is more
convenient in the install you are doing. You can also pull to
consolidation points then out to individual outlets or vice versa,
instead of pulling the bundle of cables all the way. Riser
installations are more easily done by dropping cables down rather than
pulling up. Riser installations need to be secured at regular intervals
to prevent the weight of the cables suspended from causing long term
problems.
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- One item to remember is there
is usually 1,000 feet (about 300 meters) of cable in each box.
Each cable is also marked with a distance every few feet so you
can keep track of length by reading the distance off the cable.
Before you pull any cable from the box, find the distance
marked on the cable and write it down on top of the box!
That way, you can calculate the length of each cable you pull
and more importantly, the amount remaining in the box! It's not
good to start pulling a cable and find out it's not long enough!
-
- Likewise, mark every cable with
a location it's going to. Mark it on both ends! You will save
lots of time making the correct connections, recording test data
and keeping records for moves and changes. A fine tip permanent
marker will mark the cable neatly.
- UTP cable should be installed
on special hooks, bridle rings or cable trays that limit its
bend radius and stress to preserve the performance. You cannot
lay the cable on top of ceilings or hang from the drop ceiling
hangers - in most places it's against code! Penetrations of firewalls
always require firestopping to restore fire retardancy. You also have
to keep the wire away from sources of electrical interference, like fluorescent
lights and power cables.
And,
of course, we'll remind you again that twists on the pairs must be kept
within 1/2 inch (13mm) to maintain the crosstalk performance of the
cable through the terminations.-
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- Safety
-
- Power cables are also a safety
hazard. Although this cable is called "low voltage,"
it runs in areas full of power cables that can be a shock hazard.
If you are not familiar with electrical safety, fire safety and
inspections, I strongly suggest taking a course on the NEC (National
Electric Code in the US, CEC in Canada and similar codes in other countries) to learn about these important topics. It could
save your life!
- And
when premises cabling systems are installed, they may be inspected by
local building or electrical inspectors for proper installation
according to the NEC.
-
Here is a summary of NEC references
to VDV Cabling:
| Chapter | Article | Topic | | 6 | 640 | Sound Systems | | 7 | 725 | Remote-Control,
Signaling and Power-Limited Circuits | | 7 | 760 | Fire Alarm
Signaling Systems | | 7 | 770 | Optical Fiber
Cables and Raceways | | 7 | 780 | "Smart
House" Wiring | | 8 | 800 | Telecommunications
Circuits (Telephone and LAN) | | 8 | 810 | Radio and
TV Equipment | | 8 | 820 | CATV Systems | | 8 | 830 | Network-Powered
Broadband Systems |
- Other safety considerations:
- -Hard hat, safety glasses, appropriate
gloves and steel toe shoes are recommended.
- -Observe ladder safety rules
- many installations require work above ceilings.
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- Inspection
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- Electrical inspectors do not
always inspect communications wiring. Nonetheless, take a moment
to check with local electrical inspectors before you do any work
in their jurisdictions. In most cases, the inspector of your
installation will be the same person who signs you contract,
although in some cases, the inspector will be a third party.
Make sure you know who will inspect your work before you give
your customer a final price. You must know what the inspector
will expect of you and what he or she will be looking for.
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- Installation Tips:
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- All components must be equally rated at the highest level expected from the installation, e.g. all Cat5e
rated for Cat 5e performance
- Cable must be pulled from the
reel or box without kinking
- Cable must be pulled with less
than 25 pounds of tension
- Use cable lubricant in conduit
if necessary
- Cable must not be pulled around
sharp corners or kinked
- Inspect the cable routes for
surfaces that may abrade the cable
- On riser installations (overhead
installation), try to lower the cable down, not pull up and secure carefully at recommended intervals.
- Cables must be supported to
prevent stress. Cable supports should not have sharp edges that
may distort the cable
- Cable ties must not be so tight
as to distort the jacket of the cable. They are only used to
prevent unnecessary movement of the cable, so snug is tight enough.
- Carefully follow all codes and firestop all penetrations.
Test your comprehension with the section quiz.
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