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Trunk Cable Planning & Installation Guide

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Structured Cabling Specialist Lyle Menard, RCDD/NTS, shows the features and benefits of pre-terminated copper and fiber trunking cable assemblies.

In this guide:

The purpose of this guide is to provide both designers and installers with the necessary information to properly plan and install Siemon copper and fiber trunk cabling systems. End users will also benefit from understanding trunking cable considerations.

It is strongly recommended to review all information contained in this document prior to design or installation of a trunk cable system to ensure all requirements and design considerations are met.

Trunk cables are pre-terminated copper or fiber assemblies ordered to specific lengths, ideal for data center infrastructures and backbone applications where cable distances are reasonably predictable and can be easily determined. Siemon trunk cables can be ordered with a variety of termination and performance configurations.

Calculating Trunk Cable Length

Figure 1 illustrates how to calculate a trunk cable length in a Data Center environment, but similar dimensions would be considered when using a copper or fiber trunk in a backbone/riser application.

Figure 1: Calculating Trunk Cable Length

Trunk Cable Length = (A1+A2+A3) + X + (B1+B2+B3) where:

X —Horizontal Distance
A1 —Vertical Distance (side A)
A2 —Cable Slack within the cabinet (side A)
A3 —Cable Radius transitioning out of the floor (side A)
B1 —Vertical Distance (side B)
B2 —Cable Slack within the cabinet (side B)
B3 —Cable Radius transitioning out of the floor (side B)

Shorter length copper trunk cables, i.e. - less than 25m (100 ft.), are shipped coiled flat within a box as shown below in Figure 2. Fiber trunk cables and longer length copper trunk cables are shipped on wooden reels as shown in Figure 3. For trunks shipped in boxes, it's best to remove the cable completely from the box before installing. This will eliminate any potential kinking of the outer jacket and allow the assembly to transition more easily into the pathway space.

Figure 2: Boxed Packaging (Used for short length copper trunks)

Figure 3: Reeled Trunk Packing (Used for fiber and longer length copper trunks)

In many ways, the process of installing trunking cables is similar to typical cabling installations. However, special care has to be taken to avoid damage to the connectors on the ends of the assemblies. Siemon trunking assemblies are shipped with an integrated special head end assembly (pulling grip).This is a product specifically designed to distribute the pulling tension to a portion of the cable beyond the terminated ends. It also offers a level of protection to the pre-terminated ends.

Be careful when removing this pulling grip so as not to damage the cables and connectors contained within it.

When these pulling grips are installed, the head end of the cable can get quite large in diameter. Take this into account when planning your cable pathway to insure there is sufficient space for the end to pass without damaging the cable or any other preexisting building infrastructure.

Planning for Installation

Prior to installation of a trunking system, proper consideration of the products to be installed and associated installation practices must be incorporated. Planning must then be performed based upon this information.

One of the key characteristics with any trunking product is the overall diameter of the assembly. Table 1 and Table 2 provide the O.D. of the more common varieties of the copper and fiber trunk assemblies respectively.

This information contained in Table 1 and Table 2 helps to illustrate the special attention that must be given to pathway spaces including: cable trays, conduit systems, cable managers, etc due to the size of these assemblies.

Trunk Cable Type Assembly Sleeve O.D. mm (in.) Req. Duct Diam. mm (in.)
System 6 22.86 (0.90) 63.5 (2.5)
10G 6A UTP 27.43 (1.08) 76.2 (3.0)
10G 6A F/UTP 22.86 (0.90) 63.5 (2.5)
TERA 27.43 (1.08) 76.2 (3.0)

Table 1: Copper Trunk Cable Assembly Physical Properties

Cable Type Strand Count Sleeve Diam. mm (in.) Cable Diam. mm (in.) Req. Duct Diam. mm (in.)
Non-Armored 6 44.5 (1.75) 5.8 (0.23) 69.9 (2.75)
12 44.5 (1.75) 5.8 (0.23) 69.9 (2.75)
24 44.5 (1.75) 13.7 (0.54) 69.9 (2.75)
36 63.5 (2.5) 16.5 (0.65) 88.9 (3.50)
48 63.5 (2.5) 16.0 (0.63) 88.9 (3.50)
72 63.5 (2.5) 19.5 (0.77) 88.9 (3.50)
96 88.9 (3.25) 23.9 (0.94) 108.0 (4.25)
144 88.9 (3.25) 27.9 (1.10) 108.0 (4.25)
Armored 12 44.5 (1.75) 13.0 (0.51) 69.9 (2.75)
24 44.5 (1.75) 16.0 (0.63) 88.9 (3.50)
36 63.5 (2.5) 22.4 (0.88) 88.9 (3.50)

Table 2: Fiber Trunk Cable Assembly Physical Properties

Note: Required duct diameters shown above are based on the overall size of the factory installed pulling eyes which are larger than the cable sleeves themselves. These sizes are indicated later in this document.

Pathway Sizing Considerations

When determining pathway sizing, it is important to note that there is a difference between calculated fill and actual fill. Calculated fill assumes all space is used (i.e. - no space between adjacent trunks) and trunks are not routed perfectly parallel. In reality, there is always space between trunks (as they are essentially round) and trunk cable lay is typically random along the pathway. For example, a calculated fill ratio of 50% for a cable tray can be expected to physically fill 100% of the entire cable tray due to spaces between trunk assemblies and random placement.

For cable tray systems, Siemon (and TIA) requirements specify that maximum capacity shall not exceed a calculated fill ratio of 50% to a maximum of 150mm (6 in.) inside depth. Maintaining a maximum depth serves to minimize the effects of "cable set" by reducing trunk bundle size and weight to avoid changing the geometric shape of the cables. To allow room for future expansion, and to facilitate additions and removal of cables, a lesser fill is recommended. Cable tray manufacturers should be consulted for design criteria specific to their products.

To calculate the necessary cable tray size for a specific cable type, the following procedures can be followed:

Area of Cable = ðr2 = 3.14 x (cable O.D./2)2

Area of Cable Tray = width x depth

Capacity (Calculated) = (Area of Cable Tray x 50%) / Area of Cable

Using these calculations for common cable tray sizes, Tables 3 & 4 illustrates the cable tray fill requirements for both the 10G 6A UTP and F/UTP copper trunks & the full range of Fiber Trunks:

Cable Tray Size (WxD) mm (in.) Copper Trunk O.D.
22.86mm (0.90 in.) 27.43mm (1.08 in.)
152 x 101 (6 x 4) 19 13
304 x 101 (12 x 4) 38 26
457 x 101 (18 x 4) 56 39
610 x 101 (24 x 4) 75 52
152 x 152 (6 x 6) 28 20
304 x 152 (12 x 6) 56 39
457 x 152 (18 x 6) 85 59
610 x 152 (24 x 6) 113 79

Table 3: Calculated Cable Tray Capacity Copper Trunks

Cable Tray Size (WxD) mm (in.) Fiber Trunk O.D.
  5.8mm (0.23 in.) 13.7mm (0.54 in.) 16.5mm (0.63 in.) 19.5mm (0.77 in.) 23.9mm (0.77 in.) 27.9mm (1.10 in.)
152 x 101 (6 x 4) 285 57 38 26 19 13
304 x 101 (12 x 4) 571 105 77 52 38 26
457 x 101 (18 x 4) 857 157 115 77 56 39
610 x 101 (24 x 4) 1143 210 77 103 75 52
152 x 152 (6 x 6) 428 79 58 39 28 20
304 x 152 (12 x 6) 857 157 115 77 56 39
457 x 152 (18 x 6) 1285 236 173 116 85 59
610 x 152 (24 x 6) 1714 314 231 155 113 79

Table 4: Calculated Cable Tray Capacity Fiber Trunks

Although conduits are a common pathway for a standard telecommunications infrastructure, they are not typically used as a pathway for trunk assemblies, except in areas where they may need to penetrate a wall and short sections of conduit is used as a sleeve to help maintain the overall fire rating of the wall. Tables 5 & 6 offers information to illustrate the limitations of conduits as they relate to copper and fiber trunk assemblies respectively.

Note: The primary limitation of both copper and fiber trunk assemblies as they relate to installation through sleeves is the factory installed pulling eye. For fiber trunks, these range from 44.5mm (1.75 in.) to 88.9mm (3.25 in.) and for copper trunks the pulling eye is 50.8mm (2 in.). However, the pulling eye for a copper trunk can be removed if needed to pass through the sleeve since the terminations are more robust than fiber versions.

Conduit Trade Size mm (in.) Max No. of Cables Based Upon Allowable Fill
Copper Trunk O.D.
22.86mm (0.90 in.) 27.43mm (1.08 in.)
16 (0.63) 0 0
21 (0.83) 0 0
27 (1.06) 0 0
35 (1.38) 0 0
41 (1.61) 1 0
53 (2.09) 1 1
63 (2.48) 2 2
78 (3.07) 3 3
91 (3.58) 3 3
103 (4.06) 4 4

Table 5: EMT Conduit Sizing for Copper Trunk Cables

Note: The information contained in Table 5 are based on straight runs of conduits/sleeves without bends in the pathway, which is typical for most installations where a trunk cable would be used.

Conduit Trade Size mm (in.) Fiber Trunk O.D.
  5.8mm (0.23 in.) 13.7mm (0.54 in.) 16.5mm (0.63 in.) 19.5mm (0.77 in.) 23.9mm (0.77 in.) 27.9mm (1.10 in.)
16 (0.63) 0 0 0 0 0 0
21 (0.83) 0 0 0 0 0 0
27 (1.06) 0 0 0 0 0 0
35 (1.38) 0 0 0 0 0 0
41 (1.61) 0 0 0 0 0 0
53 (2.09) 1 1 0 0 0 0
63 (2.48) 1 1 1 1 0 0
78 (3.07) 1 1 1 1 0 0
91 (3.58) 1 1 1 1 1 1
103 (4.06) 2 2 1 1 1 1

Table 6: EMT Conduit Sizing for Fiber Trunk Cables

Note: Most fiber trunks are listed in this table as "0" due to the size of the factory installed pulling eye. The O.D. of these range from 44.5mm (1.75 in.) to 88.9mm (3.25 in.). The information contained in Table 6 are based on straight runs of conduits/sleeves without bends in the pathway, which is typical for most installations where a trunk cable would be used.

Note: The information contained in Tables 5 and 6 are based on straight runs of conduits/sleeves without bends in the pathway, which is typical for most installations where a trunk cable would be used.

Tables 7 & 8 illustrate the capacity for copper and fiber trunk assemblies respectively within Siemon cable management offerings.

Note: The following capacity table is provided for planning purposes. The values shown reflect a combination of actual and calculated capacity and represent a 100% fill. These values were derived using properly dressed cables and can be adversely affected by poor cable routing practices.

Racks & Cable Managers Copper Trunk Cable O.D.
22.86mm (0.90 in.) 27.43mm (1.08 in.)
RS (Channel) 13 9
RS (Front) 7 5
RS3 (Channel) 23 16
RS3 (Front) 14 10
RS-CH 7 5
RS-CNL 35 24
RS-CNL3 23 16
RS-E (Channel) 41 28
RS-E (Front) 7 5
VPC-6 (Front) 27 18
VPC-6 (Rear) 35 24
VPC-12 (Front) 54 36
VPC-12 (Rear) 70 48

Table 7: Copper Trunk Cable Management Capacity

Note: The following capacity table is provided for planning purposes. The values shown reflect a combination of actual and calculated capacity and represent a 100% fill. These values were derived using properly dressed cables and can be adversely affected by poor cable routing practices.

Racks & Cable Managers Fiber Trunk O.D.
5.8mm (0.23 in.) 13.7mm (0.54 in.) 16.5mm (0.63 in.) 19.5mm (0.77 in.) 23.9mm (0.77 in.) 27.9mm (1.10 in.)
RS (Channel) 210 88 70 63 50 44
RS (Front) 120 50 40 36 29 25
RS3 (Channel) 354 149 117 106 85 74
RS3 (Front) 224 94 75 67 54 47
RS-CH 120 50 40 36 29 25
RS-CNL 549 230 183 165 132 115
RS-CNL3 353 148 121 106 85 74
RS-E (Channel) 633 266 211 190 152 133
RS-E (Front) 120 50 40 36 29 25
VPC-6 (Front) 414 174 138 124 99 87
VPC-6 (Rear) 549 230 183 165 132 115
VPC-12 (Front) 820 340 270 240 195 170
VPC-12 (Rear) 1100 460 360 330 260 230

Table 8: Fiber Trunk Cable Management Capacity

Impact of Cable Slack

Due to the overall size of these trunk assemblies, any slack planned into the design should be maintained well outside the cabinet/rack.

Typically these trunk cable products are used in Data Center environments where proper air flow is critical. Therefore, any slack should be kept to a minimum and if present, these coils should not interfere with air flow and cooling.

System Design

Several factors are to be considered in determining the type and performance of the trunk cable to be installed, as well as whether or not trunk cables are the best solution for a particular installation. These include, but are not limited by:

  • Long term needs of the client. This will help to dictate the performance requirements of the system, e.g. Cat 6, 10Gig, Fiber, etc.
  • Site requirements. As with any cabling infrastructure, the type and quantity of the cabling system will be limited by pathway spaces, plenum/non-plenum conditions, shielding requirements and local building codes.
  • Once these first 2 conditions are clearly identified, the next step would be to identify all your connectivity pathways to determine the quantity and length of the trunk cables to be installed.

    a. Quantity will be dictated by the number of cabinets/racks to be linked together and the port density of each.

    b. Length will be dictated by the distance between the cabinets to be linked as well as the pathway to be taken, especially when you're dealing with a fixed system such as underfloor/overhead cable tray configuration or when you're trying to maintain proper airflow in a data center environment. When trunk cables are being used as part of a building backbone system, your lengths will be dictated by the pathways provided for the vertical/horizontal links between telecommunication rooms.
  • All these measurements should be determined from the final construction drawings issued from the architect, or from the results of a detailed walk through of the jobsite. The reason for this is due to the fact that these assemblies are a custom ordered assembly, so lengths must be determined prior to the order being placed.
  • The terminology and illustration included in Figures 4 & 5 below is representative of products used in a Data Center or Backbone environment. While the products and terminology may vary from one installation to the next, the same basic concept applies.

Figure 4: 2-Connector Copper Model

Figure 5: 2-Connector Fiber Model

The minimum horizontal copper trunk length is 15m (50 ft.). Shorter lengths are possible, but note that a Channel Test must be performed using 2m (7 ft.) patchcords at both ends of the assembly. There is more detail on Channel testing later in this document.

Installation

Figure 6 below illustrates a typical crew deployment for a trunk installation. As the distance between points A and B of the cable run grows (typically anything over 100 ft.), or if there are direction changes in the cable pathway, it is recommended that an additional technician be used at the middle of the cable path and/or at each point of the direction change.

Figure 6: Installation Technician Deployment for Typical Trunking Installations

Assemblies

1. For boxed assemblies: remove from box, layout straight before installing as shown in Figure 7.

2. For reeled assemblies proper support and management of reels during installation, care of connections at very end as shown in Figure 8. Note: Fiber is different from copper with the dual reel design as seen in Figure 3 on page 3.

Figure 8: Reeled Trunk Installation

Additionally, support of these larger assemblies to the point of termination in the Telecommunications Room requires that the rear cable managers are properly mounted and utilized as shown below in Figure 9:

Figure 9: Trident Cut Ensures Each Cable is Terminated at the Proper Length

Testing

Siemon copper and fiber trunk cables are factory tested and documentation ships with every trunk.

Although all trunks are factory tested prior to shipment for applicable performance, the very nature of trunking installations can occasionally introduce damage to the connections. Discrete outlets or connectors that have been damaged during installation can often be re-terminated in the field. For this reason, it is recommended that an "installed" performance test be made to insure that there was no damage to the assembly during the installation process. Note that Siemon requires 100% transmission testing of installed cabling links/channels for warranted installations.

If you have any questions regarding the content of this document or other related issues, please contact the Siemon Technical Support or Training Department in Watertown CT at 1-800-365-2285 or your regional international Siemon sales office.

Rev. Aw, 8/07


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