Wire installation tips

UTP (Unshielded Twisted Pair) Installation Guide







Transmission performance criteria (Categories), have been established for the various grades of UTP cables.

• Category 5e – Specifies cable and connecting hardware with transmission characteristics up to 100 MHz. It differs from Category 5 by having 3 dB tighter NEXT requirements and additional requirements for PS NEXT, ELFEXT, and PS ELFEXT.
• Category 6 – Specifies cable and connecting hardware with transmission characteristics up to 200 MHz. In addition Category 6 has tighter insertion loss, NEXT, PS NEXT, ELFEXT and PS ELFEXT over Category 5e.

Cable HANDLING

Length

• The maximum horizontal cable length is 90 meters (295 feet). 10 meters is allowed for cords in the work area, and for patch cords or jumpers in the telecommunications closet.
• The maximum backbone cable length of 90 meters (295 feet). This 90 meter length assumes that 5 meters (16 feet) are needed at each end for equipment cables connecting to the backbone.

Pulling Tension

• Maximum pulling tension for a 4 pair horizontal cable is 25 LBF. Excessive pulling tensions may occur during installation. Once the damage is done, reversing the effect may not be sufficient enough to correct the problem and cable replacement is recommended. Intermediate cable pulls within the overall cable run may be necessary to avoid exceeding the maximum pulling force.

Minimum Bend Radius

• 4 pair UTP cables have a 1” Min. Bend Radius

CAUTION: Exceeding the minimum bend radius can distort the cable geometry and result in degrading of transmission performance. Repositioning of the cable to the proper bend radii may not correct the fault. Once the damage is done, the best option is replacement of the damaged cable segment.

There are two common places where exceeding the minimum bend may occur:

• At the work station wall outlet. After the cable is terminated, too often the remaining cable is jammed into the wall outlet, or worse, wrapped around itself and shoved into the outlet. A better practice would be to gently work the excess cable length back through the wall outlet into the wall.
• At the wiring closet. During routing of the cable to the terminal block or patch panel. Prior cable placement practices may have encouraged making the cable appear as formfitting or tight against the routing structure (cable tray or rack) as possible. A better practice would be to incorporate gently sweeping curves along the cable path avoiding sharp bends or changes in direction. Every effort should be made to ensure the path the cable follows has smooth gradual sweeps at any transition point.

Over Stressing

Eliminate cable stress caused by tension in suspended cable runs and tightly cinched cable bundles.

Excessive cable loading or stress can also occur if a cable is incorrectly suspended in a cable run. A recommended cable support spacing is 48" to 60" centers.

Avoid twisting of cable during installation. Excessive twisting may result in distortion of cable geometry, and in severe cases tears in the jacket.

In addition to the above guidelines extracted from TIA/EIA-568, we strongly recommend the following supplementary installation tips:

• Avoid walking or stepping on high performance cable. Avoid running over high performance cable with hand trucks or forklifts. This can exert excessive force on the cable distorting cable geometry, or crushing the pairs resulting in electrical shorts.
• Avoid the use of tightly-fitting staples, either from a staple gun or mounting in a traditional manner with a hammer. These can exert excessive force on the cable and distort the pair geometry.
• D-Rings, nail on clamps or Velcro straps all offer acceptable cable management techniques without compressing the cable.
• Avoid cables run near heat sources, as this may negatively impact cable attenuation.
• Maintain a 6" minimum spacing between cables and sources of EMI such as fluorescent lights or unshielded power lines.

Termination

Most modular jacks have the IDC connectors color coded for pair conductor assignment to either 568A or 568B wiring methods. Pin pair assignments are outlined for 568A and 568B. Maintain the same pin pair combination throughout the installation. Changing pin pair assignment can result in crossed pairs; consistency is the key. The modular jacks and cross-connect blocks employ IDC connectors to complete the circuit between the cable and the hardware. A punch down tool equipped with the appropriate blade (110 or 66) is recommended to complete the termination and properly seat the conductor.

Terminate with connecting hardware of the same category or higher. Any link which has substituted a lower category component is automatically classified to that lower category.

The maximum allowable amount of untwisting during cable termination to connecting hardware is 0.5" for Category 5e and Category 6 cables. Exceeding the recommended length of untwisting may cause performance problems. The same techniques should be employed when terminating cross-connect blocks. Maintaining jacket integrity to the point of termination aids in maintaining cable geometry and NEXT isolation from adjacent cable pairs.

Bridged taps and splices are not permitted as part of copper horizontal cabling requirements.

Adapted from material provided by Mohawk Cable