2. Determine the Locations of Low-Voltage Risers and Distribution Rooms
In most cases, the design institute, consulting firm, or client will have already specified the physical locations of the low-voltage risers and distribution rooms. In this case, check whether each distribution room meets the requirements of applicable cabling design standards, such as GB50311, Code for Engineering Design of Generic Cabling Systems. If the client has not yet specified the distribution room locations, determine suitable locations based on actual site conditions and basic equipment room requirements, then coordinate with the client to obtain approval. The locations and number of risers and distribution rooms directly affect project costs. If the original design is unsuitable, which is not uncommon, discuss it directly with the client, consulting firm, or design institute and request a design change. Document all design changes for inclusion in the final project handover documentation.
3. Outlet Schedule
The outlet schedule must be finalized before the bill of materials can be prepared. For most structured cabling projects, the design institute or consulting firm will have provided floor plans with relatively detailed outlet layouts by the time the bill of materials is prepared. Record the quantities and locations of data outlets, voice outlets, and fiber-to-the-desk outlets, then compile a detailed outlet schedule. Some structured cabling projects may have no drawings at all, including outlet layouts. In such cases, prepare the outlet schedule using the outlet quantities specified in GB50312, Code for Engineering Design of Generic Cabling Systems. This schedule is generally prepared in Excel. The figure below shows a typical cabling outlet schedule. The actual schedule may vary by project and may include additional wireless AP connections, outlets for classified networks, and IP voice outlets, which are technically data outlets.
4. Detailed Construction Drawings
Detailed construction drawings are a prerequisite for cabling installation. These drawings must be completed before the cabling project can proceed. Cable routing is a critical part of project implementation, forming the backbone of the entire cabling system. It primarily covers horizontal cable routes, vertical backbone cable routes, main distribution room locations, distribution locations, equipment room locations, cabinet locations, and building service entrance locations.
To prepare physical routing drawings, also known as conduit and cable routing drawings, determine the types of containment required, such as galvanized trunking and galvanized conduit. Identify potential obstructions, including brick walls, concrete walls, floor slabs, and partitions. Distinguish between load-bearing and non-load-bearing walls, as each requires a different approach.
Installation methods include concealed or surface-mounted runs along walls, runs above suspended ceilings, and floor-level runs. The design must specify cable routes, material types and quantities, installation methods, and required labor hours. Routing design must also account for other building systems, such as building automation, security, and fire protection.
Next, prepare an equipment room floor plan showing the locations of cabling cabinets, other network equipment cabinets, and structured cabling trunking.
Floor distribution room plans show the locations of cabling cabinets and backbone and horizontal trunking. Cabinet equipment layouts show the positions of cabling components within each cabinet. These drawings may change during construction. The final as-built drawings must incorporate all changes into the original drawings.
II. Logical Link Design for the Cabling System
1. Copper Cable Category Selection
Selection considerations include shielded or unshielded cable, Category 5e, Category 6, or Category 6A, and the required flame-retardant ratings. The final selection must be based on the authoritative documentation, including tender documents and records from technical discussions and clarification meetings.
2. Backbone Cable Type Selection
Backbone options include fiber-optic and copper cables. In practice, voice backbones generally use Category 3 multipair cables, such as 25-pair, 50-pair, or 100-pair cables. Data backbones can use four-pair twisted-pair cables or Category 5 25-pair cables, although fiber-optic cables are used in the vast majority of projects. Fiber options include single-mode and multimode cables. Determine the fiber count based on the number of users and bandwidth requirements. The final cable type must be selected based on the authoritative documentation, including tender documents and records from technical discussions and clarification meetings.
3. Material Selection for Each Cabling Subsystem
A cabling system generally includes work area, horizontal cabling, administration, vertical backbone, equipment room, and campus backbone subsystems. Materials for each subsystem must also be selected based on the authoritative documentation, including tender documents and records from technical discussions and clarification meetings.
4. Cabling System Schematic Design
The cabling system schematic, commonly called the system diagram, provides an overview of the entire cabling system. It shows the quantities, types, routes, and fiber counts of fiber-optic cables; the quantities, types, and routes of multipair cables; the quantities and categories of horizontal twisted-pair cables and the number of information outlets on each floor; and the floor locations of distribution frames and the quantities and types of connecting hardware. For larger projects, the design institute or consulting firm will generally provide a system schematic. However, not all projects include one. Where no schematic is provided, prepare it based on the selected materials, logical link relationships, tender documents, and records from technical discussions and clarification meetings.
It is therefore essential to thoroughly review the tender documents and the documents agreed upon during technical discussions and clarification meetings. These documents reflect the design intent of the client, design institute, or consulting firm. A sound understanding of their contents is essential to producing an accurate, effective design.
III. Quantity Takeoff and Pricing
1. Cabling Material Allocation Schedule
List the material models and quantities for each cabling subsystem in detail. Use your knowledge of cabling design to prepare a material allocation schedule in Excel. A standardized design spreadsheet is easy to adjust and helps prevent errors, making it an essential tool for an experienced designer. The allocation schedule captures the complete design approach and the basis for calculating material quantities. Tools that automatically calculate cabling material allocations are also available in the industry, typically using databases maintained in Excel. These tools are more accurately described as semi-automated, since basic information still needs to be entered manually. Nevertheless, they significantly improve design efficiency and accuracy.
2. Cabling Material Summary
Group the material models and quantities from each subsystem in the material allocation schedule to produce the final cabling material summary. Prepare a standardized summary in Excel showing the total quantities of all materials.
3. Project Quotation
All of the preceding work supports the preparation of the project quotation. Develop the quotation based on the material summary and ensure that it aligns with the client’s budget. The cabling industry primarily uses the following three pricing methods:
a. Estimates and Budgets Based on National Industry Authority Standards
These include standards issued by the Ministry of Industry and Information Technology and the Ministry of Construction. Costs generally fall into two main categories: direct costs and indirect costs. Refer to the cost quota standards published by the relevant industry authorities. This approach generally produces a quotation that most closely reflects the full range of cabling installation conditions, but calculating and pricing every installation activity is also the most complex method.
b. Percentage-Based Pricing for Materials, Labor, and Other Costs
For example, material prices may be calculated by adding a markup to procurement costs, with labor charged as a percentage of material costs. When domestic cabling brands are selected, this method may result in labor charges that are too low, potentially causing a project loss. The applicable percentage should therefore be increased as appropriate. This method is relatively common in the cabling industry because costs are easier to calculate than under the quota-based method. The rates in the table below should be adjusted to reflect the requirements and conditions of each project.
Labor can also be priced by outlet count, multiplying the unit installation cost by the number of outlets. This method is most commonly used by cabling installation subcontractors when quoting to system integrators.
IV. Compilation of Design Documentation
1. Cabling Drawings
These include outlet layouts, system diagrams, and conduit and cable routing drawings. Drawing production can represent a significant cost on larger projects. Construction drawings must be issued first, often in as many as five sets: one each for the client, design institute or consulting firm, main contractor, supervising consultant, and your own team. The final as-built drawings will generally require the same number of sets. Drawing production costs can therefore be substantial and should be included in the project quotation.
2. Design Proposal
Prepare the written design proposal using the design approach outlined above. Write the proposal only after the material allocation schedule and material summary have been completed. Otherwise, repeated revisions will waste time.
3. Binding the Documentation
Bind the design proposal, cabling drawings, and itemized quotation into a complete package, then hand it over to the sales team for project follow-up. At this stage, only the technical bid documentation is complete. The commercial bid documentation is generally prepared by the sales team.
A thorough understanding of the tender documents and the documents agreed upon during technical discussions and clarification meetings is essential to effective structured cabling design. We hope this guidance on structured cabling system design will be useful to cabling designers.
