Any installation error or taking the so-called "shortcut" in Category 6 wiring may lead to barely qualified or unqualified tests. Therefore, when selling products, most manufacturers advise installers to strictly abide by the installation methods specified in the wiring standard documents and the suggested methods attached to the products, which may be one of the effective methods to ensure the wiring quality before the introduction of the six types of wiring installation standards.
Wiring quality Since there are no new installation methods listed in the six specifications of AN/NZS 3080, TIA or ISO, the installation methods specified for five kinds of wiring several years ago are also applicable to six kinds of wiring. However, due to strict performance standards, Class VI wiring requires higher installation quality. Any installation error or taking the so-called "shortcut" in Category 6 wiring may lead to barely qualified or unqualified tests. Therefore, when selling products, most manufacturers advise installers to strictly abide by the installation methods specified in the wiring standard documents and the suggested methods attached to the products, which may be one of the effective methods to ensure the wiring quality before the introduction of the six types of wiring installation standards. For example, the wiring network department of the famous Molex enterprise in the United States has been emphasizing for many years that its products need to be installed by certified high-quality installers with high-quality methods. It believes that the product and its installation will have the same impact on the overall quality of the wiring system. So, what are the important problems that need to be paid attention to during the installation of six types of wiring?
1. Cable tension
Do not exceed the cable tension specified by the cable manufacturer. Excessive tension will deform the twisted pair pitch in the cable, seriously affecting the cable's ability to suppress noise (including near-end crosstalk, far-end crosstalk and its derivatives) and the structural return loss of the cable, thus changing the cable's impedance, damaging the overall return loss performance and affecting the transmission performance of high-speed local area networks (such as Gigabit Ethernet). In addition, excessive tension may also cause the pairs to spread out and damage the wires.
2. Bending radius of cable
Avoid excessive bending of cables. Because this may lead to line pairs spreading, resulting in impedance mismatch and unacceptable return loss performance. In addition, excessive bending will also affect the lay distance between cable pairs, and the change of lay distance between four pairs in cable will lead to noise suppression. Generally speaking, cable manufacturers recommend that the bending radius of installed cables should not be less than 8 times the cable diameter. For a typical Category 6 cable, the bending radius should be greater than 50 mm..
In the installation process, the most easily bent part of the cable is the junction box. A large number of cables are introduced into the distribution frame. In order to keep the wiring tidy, some cables may be pressed too tightly and bent too much, which is usually invisible and often ignored, thus reducing the performance of the wiring system. If the manufacturer provides back cable management equipment, please use these equipment according to the manufacturer's recommendation.
The bending radius of cables inside the equipment is more strictly limited. Generally speaking, the bending radius of cable during installation is 8 times the diameter of cable. In practice, the bending radius in the back box is 50mm, and the minimum bending radius of the incoming cable pipe is100 mm. 。
3. Cable compression
Avoid making the cable tie too tight and squeezing the cable. This problem is most likely to occur in large bundled cables or cable facilities, and the cables outside the bundled cables will bear greater pressure than the cables inside. Excessive pressure will deform the stranded wire inside the cable and affect its performance, which will generally make the return loss in an unqualified state. The influence of return loss will accumulate. For example, for a long cable hanging on a suspension line, a cable tie should be used every 300 mm If the cable hanging on the suspension line is 40m long, the number of times of tying is 134, and the return loss caused by each cable tying will be accumulated, thus improving the total loss. Therefore, when using cable ties, special attention should be paid to the pressure used by cable ties. As long as the strength of the binding tape can support the bundled cables.
A better method is to use cable binding pairs to bind cables together without deforming the cable sheath. This is also very important in the wiring closet, because users usually tighten the cable ties to keep the cables clean. In addition, in the wiring cabinet, the terminal wiring on the back of the distribution frame is very difficult, which is particularly easy to cause cable deformation. Therefore, some cable manufacturers, such as Molex, will encourage installers to use hooks and loop cable ties, such as Velcro brand cable ties, in their product use suggestions. These devices can avoid damaging cables due to compression, and at the same time, it is convenient to add more cables to the bundled cables, and it is easier to remove them. However, this connection mode can be easily changed by other unauthorized personnel.
4. Cable weight
When using suspension wires to support cables, the cable weight must be considered. The weight of cables varies from manufacturer to manufacturer. For example, the weight of Class VI cable No.23 (diameter 0.6mm) of Molex Enterprise Wiring Network Department is about twice that of Class V cable. If 24 Category 6 cables with the length of 1m are used, their weight is close to 1kg, while the weight of the same number of Category 5 or Super Category 5 cables is only 0.6kg. Therefore, each suspension line support point can support up to 24 cables per bundle.
5. Cable knotting
When pulling the cable from the reel, be careful that the cable may be knotted. If the cable is knotted, it should be considered as damaged and the cable should be replaced. Because even if the cable knot is straightened, the damage has already occurred, which can be verified by testing the cable. Although it is impossible for the cable knot to fail the test, all these effects will accumulate together, and when they are combined with other factors such as performance degradation caused by cable ties, the system test will fail.
6. Number of cables in a bundle of cables
When any number of cables are tied together in a long parallel length, the crosstalk will increase significantly due to the capacitive coupling between different cables with the same lay length (for example, blue wire pair to blue wire pair). This is the so-called "alien crosstalk", which has yet to be standardized or accurately defined by wiring standards. The best way to eliminate the adverse effects of foreign crosstalk is to minimize the length of parallel cables and install them into bundles in a pseudo-random way. For a long time, the method that has been adopted is to adopt "comb" wiring mode (keep it clean). Bundling cables together is the best way to avoid any two pairs of different cables being laid in parallel within the effective length. There is no shortcut or other effective method for this.
7. Peel off the cable sheath
After the cable termination point is terminated, the bare wire pair from the sheath to IDC (insulation displacement connector) must be kept to a minimum length. The shorter the length of the stripping sheath is, the more favorable it is for the pair inside the cable to keep the lay distance and realize the most effective transmission path. Excessive sheath stripping on IDC will damage the near-end crosstalk and far-end crosstalk performance of Class VI wiring system. Therefore, both TIA and ISO wiring standards stipulate the length of stripping sheath.
8. Line pair expansion
At the cable termination point, the laying distance of each pair of wires in the cable should be as close as possible to IDC. The lay lengths of each pair of wires are determined by the cable manufacturer after calculation, and changing them will adversely affect the cable performance. Although ISO and TIA super-Category 5 wiring standards stipulate the length of line-to-line dispersion (13mm), there is no similar stipulation for Category 6 wiring. The current practice is to follow the recommendations provided by the manufacturer. It is better to add a pair of stranded wires than to remove a pair of stranded wires at the end point where the contact and loop are out of order. Because this can ensure the alignment with the relevant IDC, keep the twisted distance inside the cable unchanged, and realize the best possible transmission path. Excessive dispersion of wire pairs in IDC will damage the near-end crosstalk, far-end crosstalk and return loss performance of six types of wiring systems.
9. Ambient temperature
Ambient temperature has always been a problem of Category 5 and Super Category 5 wiring, and Category 6 wiring is more serious. Environmental temperature will affect the transmission characteristics of cables, so try to avoid possible high temperature environment, such as > 60℃, which is easy to happen if the roof on the ceiling is in direct sunlight. Generally speaking, when the temperature rises, the attenuation of the cable will increase, and its influence on the long link may cause the parameters to be barely qualified or unqualified.
10.VI wiring installation points
In the six specifications of TIA and ISO, there are no new installation technical operating procedures listed. The difference is that, due to the very high performance requirements of the six types of wiring, the requirements for installation quality are also higher. The responsible manufacturer strongly recommends that the installation operation be carried out in strict accordance with the installation procedures specified in the wiring standards or provided by the manufacturer.
The most common problem in wiring is the tension of the cable when wiring. When wiring, the tension on the cable shall not exceed the maximum allowable tension specified by the cable manufacturer. Excessive tension will change the number of twisted pairs in the cable and seriously affect the anti-noise ability of the cable (NEXT, FEXT, etc. ), which leads to the loosening of twisted pair and even damage to wires.
Then, when pulling the cable from the winding wheel, pay attention to prevent the cable from kinking. If the cable is kinked, it is damaged and should be replaced. Otherwise, even if the installation engineer straightens the stranded wire, the cable will be detected during the test. Even if it passes, there will be hidden dangers, and with the increase of the number of these hidden dangers, the six types of performance margins will be minimized and failures will occur.
Another noteworthy thing is the radius of cable bending. Avoid excessive bending of the cable when routing, because this will change the layer spacing of the conductor pairs in the cable. If the tension is too large, the twisted pair will be loose, resulting in impedance mismatch and the return loss performance is not up to standard. In addition, the interlayer relationship of the four pairs in the cable may also change, resulting in a decline in anti-noise ability. Therefore, all manufacturers suggest that the bending radius of the cable should not be less than 4 times the diameter of the installed cable. This means that for a typical Category 6 cable, the bending radius needs to be greater than 25mm. Most of these problems occur in the wiring closet, and most of them will not be found, even the most careful installers may have such problems. Therefore, the manufacturer suggests to use a suitable and reasonable wire rack.
Besides, the bending radius of cables is very limited, and there are different (stricter) restrictions. Generally, the minimum bending radius of the cable during installation is 8 times of the cable diameter. In practice, this means that a bending radius of 25mm is allowed in the back box and the minimum bending radius of the guide cable is 50 mm..
It is also worth noting that the cable should not be tied too tightly to avoid crushing the cable. This problem mainly occurs when there are many cables tied and tied, and the cables at the periphery bear more pressure than the cables in the harness. Excessive pressure will deform the twisted pair in the cable, which will affect some properties of the cable, mainly because the return loss becomes the main fault. If there are many constraints and bundles, the influence of return loss will accumulate, and finally it will be manifested in the total loss. Pay special attention to this point in the wiring room, because there are many cables in the wiring room. In order to keep the cable clean and tidy, the cable may be tied too tightly, and there is one behind the connector, which is also prone to such problems. The best way to solve this problem is to use mooring hooks or rings. This device will not crush the cable, and it is easy to remove. But this method is also easy to damage the cable.
The number of cables per cable bundle is also important in wiring. When cables are laid in parallel for a certain distance, if different cable pairs in the cable bundle have the same twist ratio, there will be greater capacitive coupling, which will greatly increase the cross wiring. This phenomenon is called external cross string, although it has not been listed or accurately defined in any wiring standard so far. The best way to reduce the adverse effects of external cross-connection is to reduce the length of parallel wiring and install cable bundles randomly.
The removal of cable sheath is also very special. At the cable termination, the length of the sheath to be removed is not specified in TIA or ISO wiring standards. Removing the sheath as little as possible can ensure the twist rate and the number of twist layers of the cable. If it grows outside the skin removed by IDC. It will affect the NEXT and FEXT performance of six kinds of wiring systems.
At the cable terminal, the twist of each pair of wires in the cable is as close as possible to IDC. The cable manufacturer calculates the twist ratio, and if it is modified at will, the cable performance will be reduced. Although ISO and TIA's Class 5E wiring standards stipulate the length range (13MM) in which the pair is not twisted, it is not applicable to Class 6. Now we suggest that it is best to do it according to the manufacturer's suggestion. At the termination point, if the sequence of wire pairs and contact conductors is wrong, it is best to twist them to ensure correct alignment with IDC. This ensures the twist ratio and the number of layers in the cable, thus ensuring the best transmission performance. If the twisted pair in IDC is too loose, the NEXT and FEXT performance of the six types of wiring systems will be weakened.
1 1. Matters needing attention in six kinds of wiring construction.
Six kinds of wiring construction should pay attention to the following six matters needing attention.
1. Since the outer diameter of Category 6 cable is thicker than that of Category 5 cable, attention must be paid to the filling degree of pipe diameter in order to avoid cable entanglement (especially at elbows). Generally, it is recommended to place two Category 6 cables for conduits with an internal diameter of 20 mm ..
2. The design of the bridge is reasonable, which ensures the proper bending radius of the cable. When bypassing other trunking up, down, left and right, the turning slope should be gentle. Pay attention to whether the cables at both ends can be covered with cover plates without damaging the cables.
Three. Pay attention to the control of tension when paying off. For cables packed with spools, it is recommended to arrange at least one worker at both ends to put the spools on the self-made pull rods. The worker at the pay-off end first pre-pulls a part of the cable from the spool box for the partner at the other end of the pipeline to pull out. There should not be too many pre-tensioned cables to avoid multiple wires winding around the site.
4. After the cable traction process, the redundant cables set aside at both ends shall be sorted out and protected. When winding, it should follow the original rotation direction, and the coil diameter should not be too small. If possible, fix them on the bridge, ceiling or carton with waste thread heads, and mark them to remind other people not to move or step on them.
5. When arranging, binding and placing cables, the redundant cables should not be too long, and the cables should not be stressed by superposition. The coils should be easy to merge, and the rope should not be tied too tightly.
6. During the whole construction period, inform the technological process in time, communicate with the project leaders in the building in time, and notify Party A immediately when problems are found, so as to finish the tasks of this type of work in time before other follow-up types of work start.
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