Cable Laying: Everyting You Must Know
Apr 27, 2024
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After determining the routing of the cabling, a network cabling project initially needs to consider the laying of cable trays, which can be made of metal, conduit, or plastic (PVC) tubes based on the material used.
From the scope of tray-laying, it can be divided into work area trays, distribution (horizontal mainline) trays, and backbone (vertical mainline) trays. The type of material used is determined by the user's needs and budget.
1. Installation of Metal Conduit
1.1 Requirements for Metal Conduit Processing
The metal conduit used in structured cabling projects must comply with the specifications in the design documents. The surface should not have any perforations, cracks, or noticeable unevenness, and the interior wall should be smooth without any rust. Conduit with sufficient strength must be used where there is a high risk of mechanical damage or high stress when buried directly.
The processing of metal conduit should meet the following requirements:
1.) To prevent damage to the ethernet cables during threading, the ends of the conduit must be free of burrs and sharp edges.
2.) To minimize the shearing force on cables at the pipe ends during settling in direct burial applications, the ends should be flared.
3.)There should be no cracks or noticeable warping after bending the metal conduit. Excessive bending can reduce the effective diameter of the conduit, causing difficulties when threading cables.
4.)The bending radius of the metal conduit should not be less than the minimum allowable bending radius of the cables being threaded through it.
5.)Areas of galvanized conduit where the zinc coating has flaked off should be painted with anti-corrosive paint to extend its lifespan.
1.2 Cutting and Threading of Metal Conduit
During installation, the conduit should be cut to length as needed. Cutting can be done with a steel saw, pipe cutter, or electric pipe cutting machine, with flame cutting strictly prohibited.
For connections between pipes, and between pipes and junction or distribution boxes, threading is necessary at the pipe ends. For welding steel pipes, threading can be done with a manual die or an electric threading machine. Hard plastic pipes can be threaded with a round die.
When threading, first clamp the pipe firmly in place, then proceed with threading. If an electric threading machine is used, it can improve efficiency. After threading, clean the end of the pipe, removing any burrs from the end face and interior wall with a deburring tool, keeping the end smooth to prevent damage to the protective insulation of the cables.
1.3 Bending of Metal Conduit
The number of bends in metal conduit should be minimized during installation. Each conduit should not have more than three bends, not more than two right-angle bends, and should not have "S" or "Z" shaped bends. Too many bends can cause difficulty when threading cables. For larger cables, bends are not permitted. When construction realities do not meet these requirements, larger diameter pipes can be used or junction boxes installed at strategic points to facilitate cable threading.
Metal conduit bending is generally done with a tube bender. Place the segment to be bent inside the tube bender, with the weld seam facing the back or side to prevent flattening when bending. Step on the pipe with your foot and bend it using the bender, moving the bender gradually to achieve the desired angle. The bending radius should meet the following requirements:
1.) For exposed installations, the bending radius should generally be no less than 6 times the outer diameter of the pipe; for a single bend, no less than 4 times the outer diameter; for a row of steel pipes at corners, they should form concentric circles.
2.) For concealed installations, the bending radius should not be less than 6 times the outer diameter of the pipe; when installed underground or in concrete floor slabs, no less than 10 times the outer diameter of the pipe.
To facilitate cable threading, horizontal runs of metal conduit exceeding certain lengths and with numerous bends should include pull boxes or junction boxes; if not, a larger conduit diameter should be chosen.
1.4 Requirements for Metal Conduit Connections
The connection of metal conduit must be sturdy and well-sealed, with both pipe ends accurately aligned. The length of a coupling or threaded connector should be at least 2.2 times the outer diameter of the metal conduit. When using a short coupling for connections, construction is relatively straightforward; threaded connections offer an aesthetically pleasing solution and ensure the strength of the conduit after connection. Either method should ensure a firm and sealed junction.
When the metal conduit enters an information socket's junction box, concealed pipes can be welded into place, with the exposed length entering the box being less than 5mm. Exposed pipes should be secured with a locking nut or cap, with 2-4 threads visible beyond the locking nut.
The end of the metal conduit leading to the distribution room should facilitate connection to the cables. Conduits laid side by side should be orderly to ease identification.
1.5 Laying of Metal Conduit
1.5.1 Requirements for Concealed Metal Conduit:
Conduits embedded within walls should not exceed 50mm in diameter, while those in floor slabs should be 15-25mm; a junction box should be installed every 30m for concealed runs.
When embedded in concrete or cement, the foundation should be robust and level to prevent subsidence and ensure safe cable operation.
During connection, pipe ends must be precisely aligned, the joints should be tight to prevent water and mud infiltration.
Metal conduits must have a minimum drainage slope of 0.1%.
The burial depth for metal conduits between buildings should be no less than 0.8m; when running under footpaths, no less than 0.5m.
Pull strings or draw wires must be placed within the conduits.
The ends of metal conduits should be labeled to indicate the building, floor, room, and length.
1.5.2 Requirements When Laying Metal Conduit Exposed:
Metal conduits should be fixed with clamps, a method that is aesthetically pleasing and allows easy dismantling when needed. Where spacing of supports is specified, it should be designed accordingly. Where no design requirement exists, spacing should not exceed 3m. Support clamps should be used within 0.3m of junction boxes and at both sides of elbows.
1.5.3 Conduit and Cable Laying Within the Same Conduit:
When laying fiber optic and electrical cables within the same conduit, plastic sub-ducts should be pre-installed in concealed conduits. Fiber optics should be laid within these sub-ducts to separate them from electrical cables. The sub-duct diameter should be 2.5 times the outer diameter of the fiber optic cable.
2. Laying of Metal Cable Trays
Metal bridge trays are usually made of steel plates ranging from 0.4mm to 1.5mm thick. Compared to traditional cable trays, they have a lightweight structure, high strength, attractive appearance, require no welding, are not easily deformed, have novel connection styles, and are convenient for installation, making them ideal for laying cables.
Metal bridge trays come in two types: trough and ladder. Trough-type bridge trays refer to trough-shaped components made from bent steel plates; ladder-type bridge trays consist of side pieces and several cross members forming a ladder shape. Accessories include those necessary for connecting straight segments to each other, or to elbows, and other components for supporting and fixing. Supports and hangers include the parts that directly support the trays, such as arms, posts, post bases, hangers, and other brackets.
To prevent corrosion of metal bridge trays, several surface treatments can be used, such as electro-galvanized, painted, powder-coated, hot-dip galvanized, or made from stainless steel plates. The choice of surface treatment should be based on the project environment, importance, and durability needed. In less corrosive environments, galvanized cold-rolled steel plate trays may be used; in more corrosive environments, trays with hot-dip galvanizing or stainless steel trays may be appropriate. Given the environmental requirements of cables used in structured cabling, covered non-perforated trough-type bridge trays (referred to as metal cable trays) are often chosen.
2.1 Installation Requirements for Metal Cable Trays
The installation of metal cable trays should commence after the main civil engineering work is completed, synchronously with other ductwork (such as ventilation, water supply, and drainage pipes), or slightly afterward to avoid difficulties in cable laying after the completion of the decorative works. Installation should comply with the following requirements:
The positioning of metal cable trays should comply with construction drawing specifications, with allowable deviation dependent on the surrounding environment and not to exceed 50mm.
The level difference per meter of horizontal metal cable trays should not exceed 2mm.
Vertical metal cable trays should be perpendicular to the ground without tilting, and the deviation should not exceed 3mm.
Adjacent sections of metal cable trays should be connected using joint fitting plates, with screws fastened tightly. The horizontal alignment between two joined sections must not exceed a 2mm deviation.
For straight segments exceeding 30m or crossing a building, expansion joints should be included using expansion connection plates.
The bending radius of turns should not be less than the maximum permissible bending radius of the contained cables.
Covers should be secured with a staggered arrangement of cover plates.
Supports and hangers should be vertical, neat, firm, and free from skewing.
To avoid electromagnetic interference, bridge trays should be connected to grounding facilities in the rooms they pass through or in the floor distribution rooms using braided copper strips, maintaining an excellent electrical connection.
2.2 Support and Protection Requirements for Horizontal Subsystem Cable Laying
Support and protection requirements for pre-installed metal cable trays (metal pipes).
Trays (metal pipes) may have varying sizes depending on a one or two-floor set-up and at least two should be pre-installed, with a cross-sectional height not exceeding 25mm.
When the direct buried length exceeds 15m or when crossing or turning points of the tray routes, drawboxes should be set up for easier cable laying and maintenance.
Box covers should be accessible and flush with the floor, with waterproof measures implemented around cover areas.
Metal conduits are recommended for leading into distribution boxes.
Requirements for supporting and protecting set-up cable trays.
For horizontal runs, supporting intervals are generally 1.5-2m, and for vertical installations, supports fixed on the building structure should be less than 2m apart.
When installing metal cable trays, brackets or hangers must be set at: joint locations; intervals of 1.5-2m; 0.5m away from both ends of the tray; and turning points.
The fixed-point interval for plastic trays is generally 1m.
When laying cables beneath raised floors, the clear height within should not be less than 150mm. If the raised floor is used as an air duct for the ventilation system, the clear height should be no less than 300mm.
When using a common column as an overhead support, cables can be routed within this column. The supports should avoid grooves and cable trays, ensuring firm support.
If the exact locations of information points in the workspace and the cable laying methods are undefined, or if cables are laid under carpeted areas in workspaces, crossover boxes should be used, each serving an area of about 80cm².
Different types of cables laid in the same metal tray should be separated (using metal dividers).
When using a grid form floor combined with a groove, the following are required for laying cables and protecting supporting troughs:
Grooves and grid-shaped cable trays must be interconnected.
Groove covers should be accessible and flush with the floor, with waterproof measures taken at covers and information socket outlets.
Groove width should be less than 600mm.
2.3 Support and Protection Requirements for Backbone Subsystem Cable Laying
Cables should not be laid within elevator or pipeline shafts.
Inter-floor backbone channels should be interconnected.
Cable passage through floor holes per level in telecommunication rooms should be square or circular. Rectangular holes should not be smaller than 300mm*100mm, with at least three round steel pipes installed at circular holes, the diameter of which should be no less than 100mm.
Cable support and protection when laying backbone subsystems for building groups should comply with design requirements.
2.4 Cable Laying in Ducts
2.4.1 When laying cables in ducts, the following three scenarios exist:
1.)From a small hole to another small hole.
2.)Laying in a straight line between small holes.
3.)Laying along corners.
2.4.2 Both manual and machine methods can be used for cable laying, depending on the following:
1.)Whether other cables are present in the duct.
2.)The number of bends within the duct.
3.)The thickness and weight of the cable.
Due to these factors, it's hard to specifically recommend manual or machine traction for cable pulling; solutions must be based on the particular situation.
3. Installation of Plastic Trays
3.1 While the installation of plastic trays is theoretically similar to metal trays, there are operational differences, manifested in the following four methods:
1.)Installing suspension rods or tray-type bridges for ceiling suspensions.
2.)Employing bracket bridges for installations outside of suspended ceilings.
3.)Using brackets with dedicated trays for installations outside of suspended ceilings.
4.)Using "J" hooks installation within the suspended ceiling.
3.2 The "J" hook is the most common horizontal cabling method used within suspended ceilings. The specific construction steps are as follows:
1.)Determine the cabling route.
2.)Along the planned route, open the ceiling and push each panel aside. Numerous cables can be heavy, so to reduce the load on the ceiling, "J" hooks, hanging ropes, and other supports can be utilized to hold the cables.
3.)Start from the end farthest from the management area and pull towards it.
3.3 General methods when using brackets:
1.) Install a bracket at about every 1m on a gypsum board (hollow brick) walls.
2.) Install a bracket at about every 1.5m on concrete-structure walls.
3.4 When not using brackets, adopt the fixed Trunking method to secure the Trunking, with the following suggestions based on the size of the Trunking:
1.)For cable trunkings measuring 25mm x 20mm ~ 25mm x 30mm, each fixed point should have 2-3 fixed screws arranged in a stair pattern.
On gypsum board (hollow brick) walls, fix points at intervals of about 0.5m (the bottom of the trunking should be brush-painted with latex).
On structured wall surfaces, fix points at intervals of about 1m.
2.)For cable trunkings larger than 25mm x 30mm,each fixed point should have 3-4 fixed screws in a stair pattern, distributing the force points evenly.
On gypsum board (hollow brick) walls, fix points at intervals of about 0.3m (the bottom of the trunking should be brush-painted with latex).
On structured wall surfaces, fix points at intervals of about 1m.
3.)In addition to fixed points, drill two holes every about 1m, thread twine through, and, after cabling is completed, tie the laid twines.
4.)The methods for horizontal and vertical mainline trunking layout are the same, with the difference being one runs horizontally, and the other runs vertically.
5.)For areas where it is challenging to install horizontal mainline trunkings at the junctions with work areas, flexible metal (corrugated) tubes or plastic hoses may be used to connect.
6.)At the intersection of horizontal mainline trunkings and vertical shaft channels, a plastic protective sleeve should be installed to prevent the rough edges from damaging the cable's sheath.
7.)In workspace trunkings and horizontal mainline trunking turns, PVC trunking fittings such as outer and inner angles, straight corners, flat T-junctions, left T-junctions, right T-junctions, connectors, and end pieces should not be used to maintain aesthetic appearance.
3.5 The general process for wiring trunkings on walls is as follows:
1.)Determine the cabling route.
2.)Along the routing direction, run the cables (observe neat, visually pleasing straight lines).
3.)Secure the wiring trunking with fixing screws.
4.)Cable (fill the trunking to 70% capacity).
3.6 Matters to note upon completion of workspace trunkings and horizontal mainline trunking installations:
1.)Clean up the site to maintain cleanliness and aesthetics.
2.)Cover the plastic trunking covers with staggered placement.
3.)Patch up holes, shafts, and other junction areas.
4.)If there are gaps between the workspace trunkings, horizontal mainline trunkings, and the wall, use putty to smooth out the surfaces.
4. Concealed Conduit Wiring
Concealed conduit wiring is a method where conduits are pre-embedded in the concrete during casting, equipped with steel wires or iron wires for pulling through cables. Installation personnel can simply obtain the conduit blueprint to understand the building's floor wiring conduit system and determine "where the path lies," thereby formulating a construction plan.
For older buildings or new structures without pre-embedded conduits, it is necessary to request the building's blueprints from the property owner and inspect the site to identify the layout and direction of electrical, water, and gas pipelines. Subsequently, detailed wiring blueprints are drawn up to establish a wiring construction scheme.
For new buildings lacking pre-embedded conduits, construction can proceed in tandem with the building's decoration, which not only facilitates wiring but also maintains the building's aesthetics.
Conduits usually run from the distribution room to the information socket installation holes. Installers need to secure the '4 pair' cables at the information socket's pulling end, and then pull from the other end of the conduit to route the cables to the distribution room.
5. Cable Pulling Technique
Cable pulling involves using a pull string (typically a rope) or a soft steel wire rope to guide cables through wall conduits, ceilings, and floor conduits. The chosen method depends on the type of work to be done, the quality of the cables, and the difficulty of the wiring route (e.g., routing through hard-angled pipes is more challenging than straight pipes) and also relates to the number of cables that need to be threaded through a congested conduit as opposed to an empty one.
Regardless of the scenario, one rule applies: the connection point between the pull string and the cable should be as smooth as possible. Therefore, it's necessary to wrap electrical tape tightly around the connection point to ensure smoothness and stability.
5.1 Pulling "4 Pair" Cables
Standard "4 pair" cables are lightweight and usually do not require much preparation; simply bundling them with electrical tape to the pull string suffices.
5.1.1 If pulling multiple "4 pair" cables through a route, the following method may be used:
1.)Gather the cables into a bundle, aligning their ends.
2.)Tightly wrap electrical tape or duct tape around the outside of the cable bundle, extending 50-100mm beyond the ends, as shown in
Figure 1 Pulling line-Wrapping the ends of multiple "4 pair" cables with electrical tape
3.)Thread the pull string through the tape-wrapped bundle and tie a knot, as shown in Figure 2.
Figure 2 Pulling cable-Securing the pull string
5.1.2 If the connection point loosens during the cable pulling process, the cable and pull string must be reeled back in to create a more secure connection. To achieve this, one may take the following measures:
1.)Remove some insulation to expose 50-100mm of bare wire, as shown in Figure 3.
Figure 3 Pulling cable-Exposing bare wire
2.)Split the bare wire into two separate wires.
3.)Twist the two wires together to form a loop, as shown in Figure 4.
Figure 4 Pulling cable-Weaving wires to establish a loop for pull string connection
4.)Thread the pull string through this loop and tie a knot, then wrap electrical tape firmly around the connection point, ensuring it's tight and non-slippery.
5.2 Pulling a Single "25 Pair" Cable
For a single "25 pair" cable, the following method can be used:
1.)Bend the cable backward to form a loop approximately 150-300mm in diameter, ensuring the cable end is twisted tightly against the cable itself, as shown in Figure 5.
Figure 5 Pulling a single cable-Forming a 6–12-inch loop
2.)Tightly wrap electrical tape around the twisted cable to reinforce the loop, as shown in Figure 6.
Figure 6 Pulling a single cable-Reinforcing the loop with electrical tape
3.)Attach the pull string to the cable loop, as shown in Figure 7.
Figure 7 Pulling a single cable-Connecting the pull string to the cable loop
4.)Wrap the connection point tightly with electrical tape.
5.3 Pulling Multiple "25 Pair" or "Higher Pair" Cables
A connection type known as the "core" can be used, which is very sturdy and suitable for "hundreds of pairs" of cables, following these steps:
1.)Strip about 30cm of the cable sheath, including the insulation on the wires.
2.)Use diagonal pliers to cut the wires, leaving about twelve (a dozen).
3.)Divide the wires into two twisted wire groups, as shown in Figure 8.
Figure 8 Pulling cable with a core sleeve/hook-Dividing cable wires into two even twisted wire groups
4.)Thread the two twisted wire groups through the loop of the pull string, creating a closed loop on the other side of the cable, as shown in Figure 9.
Figure 9 Pulling cable with a core sleeve/hook-Feeding twisted wire groups through the pull string loop
5.)Twine the free ends of the cables to close the loop, as shown in Figure 10.
Figure 10 Pulling cable with a core sleeve/hook-Twisting the wires around themselves to close the cable loop
6.)Tightly wrap electrical tape around the cable, covering an area about 3-4 times the diameter of the loop, and then continue to wrap some more, as shown in Figure 11.
Figure 11 Pulling cable with a core sleeve/hook-Tightly wrapping the established core sleeve/hook with electrical tape
Some heavy cables come equipped with a pulling eye: create a loop on the cable to fix the pull string onto it. For main cables without a pulling eye, a core/hook or a separate cable grip can be used, as shown in Figure 12. Open the grip and wrap it around the cable, fitting an eye on each half of the separated part. Once the grip is attached to the cable, you can pull both eyes simultaneously, keeping the grip tightly secured on the cable.
Figure 12 Pulling cable-Using separated cable grip for pulling
6. Building's Main Trunk Cable Connection Techniques.
The main trunk cable is the central cable of a building, providing the signal transmission path from the equipment rooms to the management rooms on each floor. In new buildings, there usually exists a vertical shaft.
There are generally two methods for laying the main trunk cable in shafts:
Dropping the cable downward.
Pulling the cable upward.
Compared to upward pulling, dropping the cable downward is easier.
6.1 Dropping the Cable Downward
6.1.1 The general steps for dropping the cable downward are as follows:
1.)First, place the cable reel at the topmost floor.
2.)Install the cable reel about 3-4 meters away from the opening (hole) of the building and feed the cables from the top of the reel.
3.)Position the necessary cabling personnel at the cable reel (the number depends on the reel size and cable quality), with one worker on each floor to guide the descending cable.
4.)Start rotating the reel and pull the cable off the reel.
5.)Guide the pulled-out cable into the holes of the riser. Before doing so, place a plastic protective boot in the hole to prevent the rough edges from damaging the cable's outer sheath, as shown in Figure 13.
Figure 13 Plastic boot for cable protection
6.)Slowly drop the cable from the reel into the hole, descending downward without releasing the cable too quickly.
7.)Continue dropping the cable until the onsite cabling personnel on the next floor can guide the cable to the next hole.
8.)Following the steps above, continue releasing the cable slowly and guide it into the holes on each floor.
6.1.2 When laying vertical trunk cables through a large hole where a plastic protective sleeve cannot be used, a sheave wheel is preferable for dropping the cables. The following operations are required:
1.)Install a sheave wheel at the center of the hole, as shown in Figure 14.
Figure 14 Using a sheave wheel to drop cables downward through a large hole
2.)Pull the cable out from the sheave wheel.
3.)Following the method mentioned above, pull the cable through the holes on each floor. When the cable reaches its destination, coil each floor's cables onto a rack for future termination.
If cabling needs to pass through an area with a smaller bend radius than allowed (twisted-pair cable bending radius is 8–10 times the cable diameter, and fiber optic cable is 20–30 times the cable diameter), use a sheave wheel to resolve the bending radius issue, as shown in Figure 15.
Figure 15 Using a sheave wheel to address the bending radius of cables
6.2 Pulling the Cable Upward
For pulling the cable upwards, an electrical cable winch can be used, as shown in Figure 16.
Figure 16 A typical electric cable winch
The general procedures for pulling cables upwards are:
1.)Choose the winch model according to the quality of the cable, and operate according to the manufacturer's instructions, threading a rope into the winch first.
2.)Start the winch and drop a pull string (ensuring the pull string is strong enough to protect the cable during pulling), releasing it to the bottom floor where the cable will be placed.
3.)If there's a pull eye on the cable, attach the rope to it.
4.)Start the winch and slowly pull the cable through the holes on each floor upward.
5.)Stop the winch when the cable's end reaches the top floor.
6.)Use clamps to secure the cable at the floor hole's edge.
7.)Once all connections are made, release the cable's end from the winch.
7. Campus Cable Connection Techniques.
For cabling within a campus, there are three typical methods used: direct buried cable routing, underground conduit laying, and overhead cabling.
7.1 Cable Laying Within Conduits
7.1.1 There are four scenarios for cable laying inside conduits:
1.)From one small hole to another.
2.)Laying in a straight line between small holes.
3.)Laying along bends.
4.)Cables with PVC flame-retardant conduit.
7.1.2 Cable laying can be done manually or with machinery, depending on several factors:
1.)Whether there are other cables in the conduit.
2.)How many bends are in the conduit.
3.)The thickness and weight of the cable.
Due to these factors, it is difficult to determine whether to pull cables by hand or by machine-it must be decided based on the specific circumstances.
7.2 Overhead Cable Routing
The general steps for overhead cable routing are:
1.)Utility poles should be placed at intervals of 30-50 meters.
2.)Choose a steel wire rope based on cable quality, typically an 8-core steel wire rope.
3.)Connect the steel wire rope first.
4.)Install a hook every 0.5 meters.
5.)Install fiber optic cable.
6.)Ensure a clearance height of ≥4.5m.
When cabling overhead, the distance from electric power lines (below 1kV) sharing the same pole should not be less than 1.5m, from broadcast lines not less than 1m, and from communication lines not less than 0.6m.
Mark the end of the cable and assign it a number.
7.3 Direct Burial Cable Routing
1.)Open up the pavement.
2.)Set up manholes at bends.
3.)Bury steel pipes.
4.)Thread the cables.
8. Horizontal Cabling Techniques Within Buildings
Horizontal cabling inside buildings can use ceilings, concealed conduits, or wall ducts. Before deciding which method to use, visit the construction site to compare and select the best construction scheme.
8.1 Concealed Conduit Wiring
Concealed conduit wiring refers to the method where conduits with cable pulling wires or steel wires inside have been pre-embedded in the floor during concrete casting. Installers simply need to request the blueprint of the conduit to understand the floor's wiring conduit system and "where the path is," enabling them to create a construction plan.
For old buildings or new ones without pre-embedded conduits, obtain the building's blueprints from the owner and conduct an on-site inspection to ascertain the layout and direction of electrical, water, and gas pipelines. Then, draw detailed wiring diagrams to decide on the wiring construction scheme.
For new buildings without pre-embedded conduits, construction can progress alongside building decoration, which facilitates wiring without compromising the building's aesthetics.
Typically, conduits run from the distribution room to installation holes for information sockets. Workers simply need to secure the '4 pair' cable lines at the pulling end of the information socket, and from the other end of the conduit, pull the cable to reach the distribution room.
8.2 Ceiling Cabling
The most common method of horizontal cabling is through ceiling suspension. The specific construction steps are:
1.)Determine the cabling route.
1.)Determine the cabling route.
2.)Along the designed route, open the ceiling and push each tile aside with both hands, as shown in Figure 17.
Figure 17 A suspended ceiling with movable tiles
As multiple '4 pair' lines are heavy, to alleviate the load on the ceiling, use J-hooks, hanging ropes, and other supports to hold the cables up.
3.)For instance, when laying 24 '4 pair' cables, with two cables going to each information socket hole, you can place the cable boxes together and position the cable mouth upwards. Install 24 cable boxes in groups, as shown in Figure 18, with six boxes per group and four groups in total.
Figure 18 Installation layout for 24 '4 pair' cables; one '4 pair' per information point
4.) Add labels, writing markers on the box and numbering the cable ends.
5.) Start from the end farthest from the management area and pull towards it.
8.3 Wall Duct Wiring
General steps for wiring wall ducts include:
1.)Determine the wiring route.
2.)Lay the cables along the routing direction (ensuring a visually appealing straight line).
3.)Install a fixing screw for the duct every 1 meter.
4.)Perform the cabling (filling the duct to 70% capacity).
5.)Cover with a plastic duct cover, with covers staggered for placement
9 Fiber Optic Cabling Techniques in Buildings
In modern buildings, vertical shafts are commonly available for running fiber optic cables across various floors, necessitating fire safety measures. Many older buildings might have larger shafts with cutouts. Such shafts typically contain conduits for installing utilities like gas, water, electricity, and air conditioning lines. When using these shafts for fiber optic cable installation, the cables must be adequately protected. Cables can also be secured along wall corners.
9.1 There are two methods to run fiber optic cabling in shafts:
□ The cable can be dropped downwards.
□ The cable can be pulled upwards.
9.2 Generally, dropping the cable downwards is more straightforward than pulling it upwards. However, if transporting the cable spool machine to a higher floor becomes too difficult, pulling from below upwards is the only option. The following considerations should be taken into account during installation:
1.)Prior to laying the fiber optic cable, inspect the fiber for breaks, indentations, or other types of damage.
2.)Cable lengths should be chosen based on construction plans, ensuring that joints are positioned away from waterways, main thoroughfares, and other obstructions.
3.)The bending radius of fiber optic cables should not be less than 20 times the cable's outer diameter. Cables can be pulled using a pulling device. Technical processing should be applied to the cable ends, with pulling force exerted on the reinforcing core. The pull force must not exceed 150kg, the pulling speed should ideally be 10m/min, and the pulling length per round should not be more than 1km.
4.)A minimum of 8 meters should be allocated for fiber optic cable joints.
5.)After laying a segment of the cable, inspect for damage and conduct loss testing on the installed fiber. Only proceed with splicing once damage is ruled out.
6.)Cable splicing should be performed by specially trained individuals, using a light power meter or similar instrumentation to monitor and minimize splicing loss. After splicing, apply protective measures and install a proper cable joint sleeve.
7.)The cable ends should be wrapped with plastic tape, coiled, and kept in a reserved box, which should be mounted on a pole. If fiber optic cables are pulled up from underground onto a pole, they must be threaded through a metal pipe.
8.)Upon completion of cable installation, measure the total loss of the pathway and observe the fiber pathway's full-length waveguide attenuation characteristics curve with an Optical Time Domain Reflectometer (OTDR).
9.)Permanent markings should be placed at fiber optic splicing points and terminations.
9.3 The steps for dropping fiber optic cables downwards are as follows:
1.)Position the cable drum about 1 to 1.5 meters away from the building's floor cutout (fiber cables are usually wound on the drum, not kept in cardboard boxes) to maintain control while the drum rotates. The drum should be placed on a platform to keep it vertical at all times. The cable end should be located at the top of the drum and then pulled from there.
2.)Begin turning the spool to extract the fiber from the top. While pulling the cable, ensure that it does not exceed the prescribed minimum bending radius and maximum tension.
3.)If the cutout is small, first install a plastic guide to prevent friction between the cable and the concrete edges, which could damage the cable.
For larger openings, install a pulley wheel at the center of the opening and wrap the cable around the wheel.
4.)Slowly pull the cable from the drum until someone on the lower floor can direct the cable into the next cutout.
5.) Secure the cable with cable clips approximately every 2 meters.
