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| Division 16 Electrical |
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| 16-7 | Intrabuilding Communications Infrastructure Requirements |
| 1. | Introduction |
| A broad variety of communications systems are expected to be important over the life of campus buildings. In order for new communications technologies to be installed and maintained cost effectively, adequate physical infrastructure must be provided within campus buildings. This infrastructure will include riser systems, conduit, cable trays, and utility closets. It must be retrofitted into existing buildings, and must be designed into all new and renovated structures. This section of the planning guide describes the general and specific requirements of that intrabuilding infrastructure. |
| Communications systems are a general utility in much the same way as water or electric power systems. Unlike traditional utilities, communications systems are constantly evolving. The recommended distribution infrastructure is designed to be general purpose and flexible enough to accommodate a variety of technologies. Space is needed for cable installation and interconnection and for electronic equipment in support of the various communication technologies. Most communications utilities can share the same spaces since the physical topology and wiring requirements are similar, and no significant power is present in the cables. However, in some cases state-of-the-art communication cabling or equipment will involve new or more restrictive requirements for utility spaces, for example: |
| This section of the planning guide deals only with the physical infrastructure for cabling and electronics within a building. In general, these requirements follow the recommendations in EIA/TIA-569 "Commercial Building Standard for Telecommunications Pathways and Spaces." Subsequent sections of the planning guide define the campus' particular requirements pertaining to voice telecommunications, data communications, video distribution systems, and alarm and monitoring systems. |
| 2. | Definition of Terms |
| Some terms used in this document are defined here to avoid ambiguity. |
| 2.1 | Workstation |
| A "workstation" is an electronic device that performs some information processing or display function and connects to the communications network. Typically this will be a desktop computer with keyboard and display but might also be a telephone, a printer, an access control terminal, or some data gathering device. |
| 2.2 | Station Cable |
| A "work space" is defined as any location where a workstation might be located. Typically there will be several work spaces in a room. |
| 2.3 | Work Space |
| The premise wiring installed between each work space outlet location and the service point utility closet is referred to as a "station cable." Specific requirements for station cabling will change over time and are not included in this planning guide. Requirements will be provided for each project at the appropriate point in the design phase. |
| 2.4 | Utility Closet |
| A "utility closet" is defined as a secure, enclosed space where cable interconnections can be made and communication equipment located permanently. Utility closets will be located throughout a building with at least one on each floor. All communications utilities can share the same closet spaces but electrical power distribution panels and all other utilities must be located in other spaces. |
| 3. | General Requirements |
| Communication technologies are constantly evolving. This implies that whatever physical infrastructure is constructed must be flexible and general enough to adapt readily to new technologies as they become important to the campus. For that reason, some of the design criteria for the physical infrastructure provide capacity beyond what is needed today. However, we believe that these are reasonable criteria and that some reserve capacity and generality does not increase the cost significantly. We believe adherence to these requirements will prove economical to the campus in the long run since the resulting infrastructure will be viable for many years to come. |
| 3.1 | Topology |
| The physical topology of the campus communications network can be thought of as "hierarchical star wiring." One or more communications outlets at each work space are wired back to a utility closet where the first level of interconnection takes place. Some number of utility closets, typically encompassing one or two floors, are linked together with trunk cables. From one of those utility closets, a connection to each trunk cable is run to the main building communication utilities room, and from there to a campus regional interconnect center, which may be in another building. This hierarchical wiring plan facilitates the best management and maintenance of the communication systems. |
| Within a building, the greatest amount of wiring will be between the work spaces and the utility closets. The corresponding raceway or cable tray systems will be sized primarily by this requirement. The wiring between utility closets typically will be a few multi-pair or fiber optic trunk cables and usually can make use of the same horizontal (floor level) raceways as the work space wiring. Wiring between floors also will be primarily trunk cables leading to the main building utility space. However, provision should be made for running station cables at least one floor up or down in the riser system so that economies of scale can be realized in the provision of interconnect electronics. |
| 3.2 | Communications Equipment Locations |
| Electronic equipment and interconnect hardware for communication systems will be located in the various utility closets throughout the building. These closets are assumed to be physically secure, and environmentally provisioned for electronic equipment. |
| Typically the equipment required for communications service on any floor is to be located in closets on that floor. General equipment serving the entire building is to be located in the main utility room, usually in the basement of the building. However, certain systems such as video distribution may require the main service equipment to be located in secondary utility closets. |
| Equipment and interconnection hardware will not be located within false ceilings or other concealed or difficult to reach locations. |
| 3.3 | Flexibility |
| Different communication technologies will be used over the useful life of this infrastructure. For this reason, the design must be as general and accommodating as possible. Old technologies required little in the way of permanently installed equipment in the utility closets; current technologies require modest equipment installation throughout a building. It is not possible to predict what future technologies will require but at the very least we must provide for equipment space and power in each utility closet and a larger installation space in the main communication utilities room. |
| The distribution infrastructure also must be as flexible as possible. Small conduits will quickly fill up and may not accommodate some technologies well, for example low loss broadband or high capacity fiber optics. The most flexible distribution design involves cable trays for horizontal (floor level) distribution with large conduit sleeves for wall penetrations where necessary. Vertical trunk distribution should also be achieved with conduit sleeves. Longer conduit runs are only reasonable where horizontal offsets or long runs through physically inaccessible areas are necessary. The conduit must be as large as practical and any bend must have as large a radius as possible. |
| 3.4 | Resuability |
| Another aspect of changing technologies is the need to remove or replace cabling over time. This is another reason why cable trays are desirable and why the radius of conduit bends must be as large as possible. Past experience has shown that it is virtually impossible to remove just a few cables from a crowded or convoluted conduit system. It is often impossible to remove even the entire bundle, thus rendering the conduit unusable for any new cabling. We must avoid such problems in any new infrastructure. |
| 3.5 | Capacity |
| A modest amount of excess capacity is required in the physical distribution infrastructure both to accommodate additional technologies and to ease the transition to new technologies which replace the old. Without that capacity, it will be necessary to disrupt service to users in order to remove old cabling before installing and terminating new cabling. |
| 4. | Specific Requirements |
| The following sections define requirements for the communications infrastructure design in new or remodeled buildings. |
| 4.1 | Utility Entrance |
| The duct bank from the nearest communications vault (CV) will consist of four to twelve 4" conduits encased in reinforced concrete. The exact number will depend upon the size and usage of the building. (See "Design Parameters for the Interbuilding Communications Conduit System" (ICCS) for complete specifications.) These conduits may be used for all communication systems serving the building. |
| It is highly undesirable to feed service to any building via another building. Service always should come from the nearest CV. Any situation that appears to require otherwise must be discussed with the campus communications service units. (See paragraph 5 below.) |
| For buildings not capable of being served by the ICCS, for example above Gayley Road or off of the main campus, the service conduits shall terminate in a pull box at the perimeter of the project in a location designated by the campus engineer. Typically this will be in a location with reasonable proximity to telecommunications service. (See "Design Parameters for the Interbuilding Communications Conduit System" (ICCS) for the design of a typical communications pull box.) |
| Service conduits will penetrate the foundation wall of the building as close as possible to the main utility room. The penetration shall be sealed against water seepage. Inside the foundation wall, if the conduits do not enter the main communications service entrance room directly then a heavy gauge metal box must enclose the conduit penetration and allow access to the ends of the conduits for the purpose of pulling cables through them. The metal box must have a hinged and lockable cover plate. |
| Within the building, either conduit or enclosed metal cable tray may be used to reach the main building communications utility room. The conduit or cable tray run must be as short as possible an have as few bends as possible. In the communications utility room the conduit or cable tray may stub out no more than 6" beyond the surface it penetrates. There shall be no sharp edges on any metal fixture: conduit must be finished with a smooth bushing, cable tray must have a rolled edge or a plastic protective edge glued firmly in place. |
| 4.1.1 | Conduit Requirements |
| If conduit is used, it must be 4" diameter metal or PVC electrical conduit. At any point where a change in direction is required that is tighter than a 40" radius conduit bend, a 20" x 20" metal junction box must be provided. |
| 4.1.2 | Cable Tray Requirements |
| If cable tray is used, the cross section area must be at least 60% of the total cross section of the conduit entering the building. Metal covers on the cable tray must be removable to allow free access to the interior. If ladder-type tray is used, it must not be run through areas that are not accessible. |
| 4.2 | Communications Service Entrance Room |
| The main communications service entrance room (CSER) in each building must be designed to terminate all service cables to the building as well as building distribution cables and to accommodate permanent electronic communications equipment. This means that appropriate power and environmental controls must be provided. This room may be shared by all non-power utilities, such as telephone, data, video, alarm, monitoring, and access control. The CSER shall be located as close to the center of the building plan as practical. |
| 4.2.1 | Size |
| There must be floor space and wall space dedicated to each of the communications systems serving the building. The minimum required dimensions are specified in the sections of this guide describing the requirements unique to each service. In general, assuming all major services are present, the following CSER sizes shall be used: |
| Building Size | CSER Size |
| (Assignable Square Feet) | (feet x feet) |
| up to 50,0001 | 12 x 6 |
| 50,000 to 100,000 | 12 x 8 |
| 100,000 to 200,000 | 12 x 10 |
| 200,00 to 400,000 | 12 x 13 |
| 400,000 to 700,000 | 12 x 18 |
| above 700,000 | 12 x 24 |
| If the communications service distribution closet (see below) for the ground floor is combined with the CSER, the size of the CSER must be increased accordingly. |
| 4.2.2 | Access |
| The entrance door to the CSER shall be near the center of one of the long walls. The door shall open outward and shall be 3' 6" wide and 7' tall. The door must be lockable and keyed in accordance with the campus utility space master plan. Access to the CSER shall not require passage through any assignable or otherwise occupied space. |
| 4.2.3 | Cable Pathway Penetrations |
| The conduit or cable tray penetrations shall be as near the entrance door as practical. |
| 4.2.4 | Provisioning |
| All walls of the CSER shall be covered with 3/4 inch AC fire retardant plywood attached so that it is capable of supporting 50 pounds per linear foot of wall space. |
| Dedicated 120 VAC, 20 amp, double duplex outlets shall be provided for each communications service (see following sections for details). In addition, a separate 120 VAC, 20 amp circuit shall be provided for temporary equipment (e.g. test equipment) with duplex outlets every 6 feet along the CSER walls. All outlets are to be located approximately 12² above the finished floor and clearly labeled with the breaker and panel number from which it is fed. |
| Lighting shall be provided to ensure a minimum of 50 foot candles, measured 3' above the finished floor. |
| A 3/4" conduit shall be provided between the CSER and the location of the main building grounding electrode. |
| 4.2.5 | Environmental Considerations |
| HVAC shall be included in the design of the CSER to maintain temperature below 85 degrees Fahrenheit. Planning for eventual provisioning, as required, of continuous HVAC (24 hours per day and 365 days per year) shall be included in the initial design. A positive pressure shall be maintained with a minimum of one air change per hour, or as required by applicable code. When installation of active devices (heat producing equipment) is known to be required, a sufficient number of air changes shall be provided to dissipate the heat. |
| 4.2.6 | Finish Details |
| All surfaces shall be light in color and treated to minimize dust creation. The room shall not have a finished ceiling unless required for fire resistance or environmental reasons. |
| 4.3 | Riser Systems |
| From the building communications service entrance room, conduit or raceway must be provided vertically to primary service distribution closets on each floor of the building. Ideally, these closets are stacked so that all that is required is conduit nipples between floors. Vertically mounted ladder rack must be mounted to the wall between incoming and outgoing nipples within the closets. The ladder rack will be used to provide strain-relief for cables transiting closets within the riser system. If the building plan is large enough to require a second communications closet on one or more floors, then the riser pathway must be duplicated from the service entrance room up through this second set of closets. |
| 4.3.1 | Vertical Pathway Size |
| A minimum of three 4" diameter conduits, or equivalent raceway cross section, must be provided between the communications service distribution closets on adjacent floors and between the CSER and the first closet. |
| 4.3.2 | Vertical Pathway Topology |
| If the service distribution communications closets are not aligned vertically above one another, the conduits interconnecting them will have horizontal offsets. There shall be no more than two 90 degree bends in any such conduit run. Any bend must have an inside radius 10 times the diameter of the conduit (typically 40"). If these conditions can not be met, then intermediate pull boxes must be used wherever a non-standard transition is required. This pull box must at least 20" x 20" in the plane of the attached conduits, and 6" deep. All conduit other than simple nipples between floors must be fitted with a continuous 1/4" nylon pull rope. |
| 4.3.3 | Access to the Roof |
| In any building with more than 50,000 ASF a minimum of two 3" and one 3/4" conduits shall extend from the topmost service distribution closet to the roof. Termination shall be in a weatherproof NEMA metal enclosure. |
| 4.3.4 | Cable Pull Anchors |
| In the topmost service distribution closets, pull anchors shall be provided to assist in installation of large trunk cables. A suitable anchor would be a bolt eye attached to the ceiling above the vertical conduit penetrations capable of holding at least 500 pounds. |
| 4.3.5 | Pathway Finish Details |
| Conduit shall be free of burrs or sharp edges. Sheet metal sleeves, if used, shall have rolled edges. Conduits or sleeves shall protrude at least 1² from the surface they penetrate but no more than 3². Conduits shall be fitted with a smooth bushing. All penetrations shall be filled with fire blocking material. |
| 4.4 | Communications Service Distribution Closets |
| Communications service distribution closets (CSDC) are where the interconnection between station cables and the communications distribution systems are made. Electronic equipment may be located in any CSDC. The design and purpose of the building may dictate which communication systems will appear in which CSDC but in general it should be assumed that at least data and voice service will be present in every CSDC. |
| 4.4.1 | Location of the CSDC |
| There must be a CSDC within 295 cable feet of any communications outlet location. Allow for 15 feet of cable within the utility room. If this requirement can not be met, additional CSDC¹s will be required on any such floor. (See above for riser considerations.) |
| 4.4.2 | Size of the CSDC |
| The sizes given below for typical communications service distribution closets are based on the needs of data and voice communications systems. Typically alarm and access control systems can be accommodated in this size as well. Video distribution may require a CSDC to be somewhat larger to accommodate an additional equipment rack and wall space (See the Construction Guide section on Video Distribution Requirements). |
| Area Served from CSDC | CSDC Size |
| (Square Feet) | (Feet x Feet) |
| up to 5,000 | 10 x 7 |
| 5,000 to 8,000 | 10 x 9 |
| 8,000 to 15,000 | 10 x 11 |
| above 15,000 | 10 x 14 |
| 4.4.3 | Access |
| The entrance door to the CSDC shall be near the center of one of the long walls. The door shall open outward and shall be 3¹ wide and 7¹ tall. The door must be lockable and keyed in accordance with the campus utility space master plan. Access to the CSDC shall not require passage through any assignable or otherwise occupied space. |
| 4.4.4 | Cable Pathway Penetrations |
| The conduit or cable tray penetrations shall be as near the entrance door as practical. |
| 4.4.5 | Provisioning of the CSDC |
| All walls of the CSDC shall be covered with 3/4 inch AC fire retardant plywood attached so that it is capable of supporting 50 pounds per linear foot of wall space. |
| Dedicated 120 VAC, 20 amp, double duplex outlets shall be provided for each communications service (see following sections for details). In addition, a separate 120 VAC, 15 amp circuit shall be provided for temporary equipment (e.g. test equipment) with duplex outlets every 6 feet along the CSDC walls. All outlets are to be located approximately 12" above the finished floor and clearly labeled with the panel and breaker number from which it is fed. |
| Lighting shall be provided to ensure a minimum of 50 foot candles, measured 3' above the finished floor. |
| 4.4.6 | Environmental Considerstions |
| HVAC shall be included in the design of the CSDC to maintain temperature below 85 degrees Fahrenheit. Planning for eventual provisioning, as required, of continuous HVAC (24 hours per day and 365 days per year) shall be included in the initial design. A positive pressure shall be maintained with a minimum of one air change per hour, or as required by applicable code. When installation of active devices (heat producing equipment) is known to be required, a sufficient number of air changes shall be provided to dissipate the heat. |
| 4.4.7 | Finish Details |
| All surfaces shall be light in color and treated to minimize dust creation. The room shall not have a finished ceiling unless required for fire resistance or environmental reasons. |
| 4.5 | Floor Level Distribution |
| The floor level distribution infrastructure primarily supports cabling from each service distribution closet to outlet locations within its service area. In addition, trunk cabling may need to be installed between closets if there is more than one on a floor. The main cable pathway system serving a particular floor of a building is referred to as the "horizontal distribution infrastructure." Additional raceway or conduit may be necessary in order to reach individual communications outlet locations at the work spaces. |
| The use of air plenum spaces for horizontal distribution infrastructure should be avoided. The cable necessary to meet fire code requirements is many times more expensive than regular cable. |
| 4.5.1 | Horizontal Disbribution Infrastructures |
| This infrastructure normally will be installed in the ceiling space of corridors, both central and peripheral, on all floors of the building. It is essential that this infrastructure be flexible and accessible. Cable tray is preferred, although metal raceway and "J" hook suspension systems are acceptable. |
| 4.5.1.1 | Cable Tray |
| Cable tray should be "ladder type," suspended above any false ceiling. A typical tray will be 12" wide by 4" (this tray may be shared by all non-power utilities). Alternatively, the tray may be sized to provide 1 square inch of cross section for every 100 square feet of floor area served. |
| 4.5.1.2 | Access to the Cable Tray |
| A minimum of 12" access headroom shall be provided and maintained above the cable tray. Care shall be taken to ensure that other building components (e.g. air conditioning ducts) do not restrict access to trays. |
| If the cable tray traverses an inaccessible area, such as a fire resistant sheet rock ceiling area, the tray shall have solid sides and bottom and no top. Alternatively, an equivalent cross section of conduit may be provided to span the inaccessible area. |
| 4.5.1.3 | Raceway |
| Raceway may be located along the top of corridor walls, just below any false ceiling. It must be at least 4" by 6" and mounted so that the side cover is removable at any point. Raceway may be used above the false ceiling as well, and may be mounted so that the top cover is removable at any point. |
| 4.5.2 | Work Space Distribution |
| Work space distribution infrastructure extends between the horizontal distribution infrastructure and work space communications outlet locations. Typically conduit will be installed from just above the cable trays through the walls and ceiling spaces to a standard electrical fixture box. Within a room, raceway might be used where a large number of communications outlets are anticipated. |
| 4.5.2.1 | Conduit Requirements |
| Ideally there will be a separate conduit for each outlet. In no case may a work space service conduit serve more than 2 outlet locations. If a conduit serves only one location, it shall be 1 1/4" EMT or PVC. If a conduit serves two locations, the run to the first location shall be 1 1/2" EMT or PVC and the intermediate run shall be 1 1/4." See Figure 1 for details. |
| Wherever a change of direction occurs, radius bends must be used: condolet's or other sharp change of direction components are not permitted. The inside radius of bends must be 10 times the diameter of the conduit. There may be no more than two 90 degree bends in any unbroken run. All installed conduit must include a fish tape or pull cord. |
| If a run must be broken with a pull box, it shall be placed in an exposed manner and location, and readily accessible. Pull or splice boxes shall not be placed in a false ceiling space unless immediately above a suitably marked, hinged panel. |
| If cable tray is used for the main horizontal distribution, the work space conduit must extend to a point just above the near side of the tray. If raceway is used, the work space conduit must penetrate the raceway with a standard conduit connector. |
| Variations on the Œseparate conduit per outlet¹ rule may be proposed but must be reviewed and approved by the relevant campus service unit. For example, 1-1/2" by 3" raceway might be used as a local distribution infrastructure within a laboratory or classroom. This might be served by a raceway section leading to the corridor cable tray, or by a (set of) larger conduits between the cable tray and the local raceway. |
| Conduits shall be clearly labeled at both ends designating the outlet location(s) served. The numbering scheme shall be room number plus a suffix to guarantee uniqueness, e.g. 143-1. |
| 4.5.2.2 | Raceway Requirements |
| In some cases, especially in remodeling existing structures, it may be impractical to install conduit between the cable tray and the outlet locations. Surface mounted raceway is an acceptable alternative. |
| If only communications cable is to be installed, a high quality plastic raceway may be used. Cross section may be 1/2² x 1 1/4². The cover shall be either hinged or completely removable. The raceway shall be fastened every 18² with screw anchors. |
| If split raceway is used so that power can be provided as well, the power wiring shall be installed in the lower half of the raceway. This is so that the equipment power cables will not drape on top of the communications cables. Similar considerations apply to raceway built in to moveable partition walls. |
| Raceway shall be colored or painted to match the wall color. |
| 4.5.2.3 | False Ceiling Pathway Requirements |
| In some cases it will be practical to install conduit only through partitio walls and then use false ceiling space to run cables to vertical conduit leading to outlet locations. |
| Inaccessible ceiling areas, such as lock-in type ceiling tiles, drywall or plaster, shall not be used as distribution pathways. Only areas with ceiling tiles of the removable or lay-in type and placed at a maximum height of 11 ft above the floor may be used. |
| The design shall provide a suitable means and method for supporting cables and wires crossing the false ceiling space. The suspended ceiling support wire or rod shall not be used for this purpose. Wire or cable shall not be laid directly on the ceiling tile or rails. |
| A minimum of 6" clear vertical space shall be available above the ceiling tiles for the distribution wiring pathway. |
| 4.6 | Communication Outlet Fixtures |
| Specific requirements for the location and density of outlets is given in the sections of this planning guide devoted to specific communications services. The requirements given here are for the general infrastructure. |
| At each outlet location a 4" x 4" x 2-1/4" deep electrical fixture box is to be provided and firmly attached to wall studs. If the fixture box is to serve only one communications service, a single gang plaster ring shall be fitted on the box. If two services are sharing the same box, a double gang plaster ring shall be fitted. |
| Unless it is known that service will be established at a particular box, each box is to be finished with a plain solid cover plate. |
| 5. | Review Requirements |
| Review of construction plans involving communication infrastructure should be initiated as early as possible with the relevant campus service units. Reviews should occur at the program planning stage, and at each major design review stage. Approval shall be obtained from the above office(s) before construction plans may be considered final. |
| 1 See appendix A2 in the EIA/TIA-569 standard for discussion of buildings under 10,000 ASF. |
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