Specifications

Tension.
Too much tension will give you a headache.
UTP. To avoid stretching, pulling tension should
not exceed 110 N (25 lb/ft.). Pulling too hard untwists
the pairs, and you know what that does. Use supports
and trays in cable runs to minimize sagging, which
pulls on the pairs and degrades performance.
2- and 4-fiber horizontal: The maximum tensile
load is 222 N (50 lb/ft.).
Cinching.
Take care not to cinch cable bundles tightly, which
causes stress and degrades performance. Tie cable
bundles loosely. And never ever staple cables.
Connecting hardware.
Twisted pair. It may seem obvious, but use
connecting hardware of the same category or higher.
The transmission of your components will always be
the lowest category in the link. So, if you’re using
CAT6 cable, use CAT6 connectors.
Fiber. Fiber is much more difficult to terminate
in the field than copper cable. If you have a poor
fiber polish and alignment, you’ll lose a great deal
of performance. Rather than field polishing the
termination, use pre-polished connectors.
Miscellaneous considerations.
• Visually inspect the cable installation for proper
terminations, bend radius, tension, etc.
• Don’t uncoil UTP on a spool. It can cause kinks
and NEXT failures. Rotate the spool instead.
• Plan for 12 inches of slack cable behind wall outlets
for possible future reterminations.
• As always, avoid EMI. And don’t run UTP cable over
fluorescent lights, etc.
You can invest in the best cable and hardware, but
if they’re not installed properly, they won’t work, or
at least they won’t work well. Protect your investment
and follow the guidelines as outlined in TIA/EIA-568-B.1.
The most important practices involve:
1. Cable pair twists.
2. Bend radius.
3. Tension.
4. Cinching.
5. Connecting hardware.
There are others, but if you do nothing else,
mind these.
Cable pair twists.
This is the most important guideline you can
follow for twisted-pair cable. The
pair twists are responsible for much
of cable’s performance. If you lose
the twists, you lose performance.
Remember this.
When terminating CAT5e or
higher, maintain pair twists to
within 13 mm (0.5 in.) from the
point of termination. And remove
as little of the sheath as possible.
Bend radius.
Next on your installation ”to-do” list is bend
radius. If you bend twisted-pair cable too much, you
loosen the twists, and yes, lose performance. The
following bend radii are under no-load conditions:
UTP horizontal. 4 times the cable diameter.
ScTP horizontal. 8 times the
cable diameter.
Multipair backbone. 10 times
the cable diameter.
2- and 4-fiber horizontal.
Not less than 25 mm (0.98 in.).
Fiber backbone: Not less than
10 times the cable diameter, or as
recommended by the manufacturer.
Even though there is no standard
at this time for patch cable bend
radius, be aware of that, too.
26
Black Box Guide to Structured Cabling
Section NameSection Name
Installation & Testing
Cable installation practices
UTP bend radius = 4X cable diameter
Observe proper bend radius.
0.5"
(13 mm)
Keep jacket removal
and untwists to a minimum.
Keep cable wraps snug
but do not pull or crush cables.