Horizontal Cabling Distance Overrun in a Renovated Wing
A hospital is renovating a 1960s wing into outpatient clinics. The design calls for a 90 m permanent link from a new telecommunications room (TR) on the second floor to exam rooms along a 78 m corridor. The building has a 3.6 m ceiling plenum with existing ductwork and a fire-rated corridor wall 40 m from the TR. The contractor proposes routing cable in the corridor plenum above the fire wall with no firestop, arguing the plenum is continuous and the cable is plenum-rated. Field measurements show the longest proposed path is 96 m including slack and vertical drops. The owner wants Category 6A for 10GBASE-T to future-proof imaging workstations.
1. Evaluate the proposed 96 m permanent link against the standard channel/ link limits and recommend a design change.
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Category 6A permanent link limit is 90 m (with 100 m channel including patch cords). A 96 m permanent link exceeds the limit even before patch cords, so 10GBASE-T performance cannot be assured. The correct move is to add an intermediate TR or consolidation point so no permanent link exceeds 90 m, and to recalculate the channel with actual patch-cord lengths. Simply accepting the 96 m run and hoping for the best is not defensible; the design must be re-routed or re-architected. Note that adding a TR introduces backbone and power/cooling requirements that must be coordinated with the architecture team.
2. Assess the firestopping proposal and state what the design must require.
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A fire-rated corridor wall must be penetrated only with an approved firestop system rated to the wall's fire-resistance rating. Plenum-rated cable addresses smoke and flame spread of the cable itself, not the integrity of the rated assembly. The design must require firestop assemblies listed for the cable type and bundle configuration, installed by qualified personnel, with documentation. The contractor's argument that the plenum is continuous is incorrect; the wall is a rated barrier. This must be captured in the specifications and inspected.
3. The owner asks whether Category 6 would save money while still supporting the imaging workstations. How do you respond?
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Category 6 supports 10GBASE-T only to limited distances (commonly cited around 55 m for 10GBASE-T depending on alien crosstalk conditions), which is shorter than many of these runs. Given the 90 m design and the stated 10GBASE-T requirement, Category 6A is the defensible choice. If the owner insists on Category 6, the design would need shorter links (more TRs) or a documented acceptance that some outlets will not support 10GBASE-T. That trade-off should be recorded as an owner decision, not silently absorbed by the designer.