Standards for wiring telecommunications networks in Cornwall Council buildings
Introduction 3
Horizontal distribution cabling 4
Telephone distribution cabling 6
Network wiring centres 7
Backbone cabling 9
Telephone backbone 11
Implementation 13
Warranty 13
Documentation and labelling 13
Acceptance 14
Introduction
1. This document outlines the standards to which telecommunications cabling must conform for any new works, additions to existing installations and repairs. Standards for electrical installation are documented elsewhere. Where a supplier wishes to respond to both the telecommunications and electrical elements of a given tender both standards will apply.
2. New cabling installations will be expected to support the following applications:
• Ethernet local area networks at 10Mbps, 100Mbps and 1000Mbps
• Power over Ethernet
• PABX analogue extensions
• PABX digital extensions
• ISDN2 circuits
• PTO analogue circuits
• Video – baseband and RGB
• RS232 at up to 19.2Kbps
3. For each installation a schedule will be supplied which will document the detail of the requirement together with any variations to this specification. As well as complete installations suppliers may be invited to provide a “terminate and test” service in relation to cables run in by others.
4. The following conditions will apply in all cases:
• A documented network design including outlet quantity and layout must be agreed with Cornwall Council’s project manager before work commences
• Acceptance testing will be required to confirm that the installed system meets the defined specifications and standards
• All cabling work will be fully documented
5. In addition, unless otherwise agreed or specified in the schedule:
• Wiring to final outlet destination points will be via 4 pair category 5 (enhanced) or category 6 UTP cables
• Links between wiring closets and campus buildings will be via fibre optic cables
• Voice connections between wiring closets and exchanges will be via copper pair cables
• Additions to existing installations will use components from the same manufacturer
Horizontal distribution cabling
Specification and standards
6. The cable and component quality and the installation and termination techniques must, as a minimum, comply with all relevant parts of EN50173 and EN50174, category 5 enhanced standards to support application class D.
7. The cable is to be unshielded four twisted pair, with nominal impedance 100W. Outlets will conform to EN 28877 (eight position modular connector) and be capable of receiving 24 AWG solid and stranded wires terminated by insulation displacement methods. Termination is to be to the T568B standard.
8. The following installation standards will apply:
• The length of each horizontal cable from patch panel to telecommunications outlet is not to exceed 90 metres
• Maximum bending radius during installation of 75mm
• Maximum final bending radius of 25mm
• Maximum pulling load of 25 lb/ft
• Cables to be secured at both ends using the fixings provided
• Cable ties are not to be over tightened to a point where they cause strain on the cable sheathing
• Segregation from power of 150mm unless contained in purpose designed multi compartment trunking, in which case the length of the parallel run should be kept to a minimum
Density of outlet distribution
9. Unless otherwise specified in the schedule, the density of outlets will be based on floor area and will be as follows, where the term “outlet” should be taken to mean a single RJ45 point. The outlets will be evenly distributed around the area.
• For a data only installation in a normal work area the minimum density is to be 2 outlets (1 double outlet) for every 9 sq m
• For a voice and data installation in a normal work area the minimum density is to be 4 outlets (2 double outlets) for every 9 sq m
• For installations in classrooms the minimum density is to be 4 outlets (2 double outlets) for every 9 sq m
• For other locations such as computer rooms and meeting rooms the density may be higher or lower than normal and will be specified in the schedule
Outlet location and cable containment
10. In all cases, double outlets will be mounted on single gang faceplates and quad outlets will be mounted on double faceplates.
11. All containment will be surface mounted unless otherwise stated. Perimeter trunking at dado rail height is the preferred method of containment in areas of normal outlet density. Where possible, the bottom of the trunking should be at least 25 mm above normal desk height. Trunking at skirting level should be used only where dado trunking is impracticable. Existing trunking should be used where feasible in which case the supplier will be responsible for fitting suitable back boxes. Individual wall mounted back boxes should be used in areas of low outlet density.
12. Outlets will not be mounted on moveable partition walls unless an adequate distribution cannot otherwise be achieved; in such circumstances the preferred solution is to install the horizontal termination in the ceiling space above. Where the smaller dimension of a room exceeds 8m, provision will be made for locating outlets remotely from the walls using purpose-made poles or floor boxes.
13. Installation practice is to ensure that the cable is not subjected to excessive lateral or longitudinal strain in installation and that support by tie wrap of cable bundles is provided at 0.5m intervals on vertical runs and 1.5m intervals on horizontal runs. Minimum bending radii of 20 times cable diameter during installation and 10 times diameter after installation will be maintained at all times. Cable pair twist must be maintained during stripping and termination.
14. Where main cable runs are located above suspended ceilings or below floors, basket or tray fixed to the building structure will be used. This will also apply to cable run between building floor levels. Under floor installations in particular must be adequately protected from attack by vermin. Baskets/trays should not be more than 60% full in a new installation. Under no circumstances will cables be loose laid.
Service to desks
15. The supplier may be required to provide the service to the desks in which case the following will apply:
• Extension from horizontal outlet to user workplace will normally be by drop leads direct to the desk, terminated at each end in RJ45 plugs. These cables will be factory made and conform to the cable and connector specifications required to meet EN50173 enhanced application class D standards.
• The cable feed into the desk should be installed through appropriate desk cable management. Where cable management does not exist, cable ties, trunking etc must be used to secure cables appropriately. Approximately one metre free tail should be left for equipment connection and the remainder neatly contained within the desk.
Testing of UTP cabling
16. Unless otherwise specified in the schedule, 100% of the installed UTP cables will be tested in accordance with the latest draft of EIA/TIA TSB67. The tests are to include:
• Length
• Wire map
• Attenuation
• NEXT
• ELFEXT
• ACR
• Return loss
• Propagation delay
• Delay skew
17. NEXT, ELFEXT and ACR should ideally be tested under power sum conditions.
18. Details of the test equipment to be used and documentary evidence of regular calibration will be required.
Telephone distribution cabling
General principles
19. Three types of telephony service may be encountered:
• IP Telephony as part of a structured cabling system
• PBX-based with separate distribution using voice grade cable
• PBX-based as part of a structured cabling system
20. IP telephony requires only compatibility with power over ethernet. Separate distribution using voice grade cable will follow the standards set out in paragraphs 52 and 53. The remainder of this section applies where PBX-based telephony is used as part of a structured cabling system. The precise wiring configuration will be specified in the schedule.
21. The telephone system supplier will terminate the extension wiring on a test jack frame (TJF). The wiring contractor will terminate the distribution wiring on an adjacent main distribution frame (MDF) which will, in turn, be connected by multi pair voice grade cable to voice patch panels in the main (or only) wiring centre. Where there is more than one wiring centre the distribution will be in accordance with paragraphs 49-51.
22. An additional provision of 20% beyond that which is currently required should be made to allow future phone provision to be satisfied through patching rather than physical rewiring. Distribution frames and boxes should not be mounted at floor or ceiling level or behind furniture or cabinets.
Specification and standards
23. Unless otherwise specified, two pairs will be connected to each voice patch panel outlet; pair 1 will be connected to RJ45 pins 4&5 and pair 2 will be connected to pins 3 and 6. The MDF must be connected by a dedicated 6mm2 cable to a clean earth point in accordance with BS7671.
24. All voice cabling is to comply with BS6701. Multi-pair copper cable within buildings is to conform to the BT CW1308 specification and will be terminated on punch-down strips type 237A.
25. The frames onto which the wires are connected will be clearly labelled in ascending numerical order, allowing for each connected circuit to be documented with a frame, row, and location detail, e.g. 1A-39-6 will relate to a circuit connected to frame 1A, row 39, location 6.
26. The following jumper wire colours will be used with punch-down strips:
• Green/yellow ISDN connections
• Blue/yellow wire Analogue connections
27. At no point should jumper wires be pulled tight or bend more than 90o.
Testing of telephone cabling
28. Unless otherwise specified in the schedule, 100% of the installed cabling will be tested for:
• Continuity
• Attenuation
• Insulation
• Wire map
Network wiring centres
Location
29. Suitable locations for wiring centres must be agreed in advance and will be specified in the schedule. Office areas, kitchens and any areas subject to excessive dust, damp or temperature extremes are not to be used.
Patch frames
30. The schedule will specify whether patch panels are to be installed in an open frame or an enclosed cabinet. Enclosed cabinets should have a toughened glass or perspex lockable front door and removable steel sides. Floor standing cabinets should have a lockable steel back door.
31. The cabinet or frame must be equipped with effective vertical and horizontal cable management. The frame is to be a minimum of 700mm wide to permit tidy vertical routing of patch cords. The density of patch sockets is to be no more than 24 per row. Horizontal cable management must be included every two rows. To facilitate cable tracing vertical cable management must take the form of bars or loops rather than plates with holes.
32. Unless otherwise specified, the standard configuration for wiring frames should be as shown in the diagram below. Where IP telephony is in use the space designated voice patch may be occupied by PoE switches instead.
33. Horizontal cable management to be fitted every 2u.
34. The total space occupied by the outlet patch and voice patch must not exceed 75% of the frame capacity. To meet this condition in large installations multiple identical frames should be combined with clear access between. The outlet and voice patch panels should then be evenly distributed across the frames.
35. Cabinets and frames up to 22u in height are to be equipped with a power strip with a minimum of six 13A sockets. Larger cabinets and frames are to be equipped with a minimum of 12 sockets. Sockets should be off set from the centre line and/or spaced so as to permit the use of typical low voltage power supply units. If specified in the schedule a rack mounted UPS is to be supplied and installed as shown in the diagram and the power strip connected to its output.
36. The mains supply to the cabinet or frame is to be taken from a switched/fused spur fed from a clean radial circuit and labelled with the distribution board reference. In addition the frame must be connected to a clean earth source in accordance with current IEE wiring regulations BS7671.
Patch cables
37. Patch cables will be factory made and conform to the cable and connector specifications required to meet EN50173 enhanced application class D standards. The following coloured cables will be used to signify the type of connection:
• GREY Non critical data
• RED Critical voice or data
• BLUE Non critical voice
• GREEN Cross over between active devices
• BLACK DMZ/restricted access
• MAROON ISDN or BT direct dial (ISDN lines have yellow tag on end)
• YELLOW Test environments
• ORANGE Public/shared networks
• BROWN Uncontrolled/untrusted networks
• PINK Server management (including ILO)
38. Patch cables must be of appropriate length and routed tidily using horizontal and vertical cable management.
Backbone cabling
Fibre optic backbone
39. Unless otherwise specified in the schedule, new optical fibre cable shall consist of multimode graded-index 50/125 mm fibres meeting the following specifications:
Mechanical performance
• Cable minimum bend radius: 20 times cable diameter during installation and 10 times cable diameter after installation
• Buffered fibre minimum bend radius:19 mm
• Operating temperature range: -10 to +50 degrees C
• Storage temperature range: - 40 to +70 degrees C
Optical specifications
40. Maximum fibre loss shall meet or exceed the following specifications:
• 3.0 dB/km at 850 nm
• 1.0 dB/km at 1300 nm
41. Minimum bandwidth shall meet or exceed the following specifications:
• 400 MHz-km at 850 nm
• 600 MHz-km at 1300 nm
• Numerical aperture: 0.2
Fibre optic connectors
42. SC style connectors shall be used which meet or exceed the following specifications:
• Operating temperature: -10 to +75 degrees C
• Average loss: 0.3 dB