TR Sizing for a Growing Floor
You are designing the telecommunications room for a 2,400 m² (26,000 ft²) floor of a new office building. The architect has given you a 2.4 m × 3.0 m (8 ft × 10 ft) room with a single 900 mm (36 in) door opening inward, one wall shared with an electrical closet, and a dropped ceiling at 2.7 m (9 ft). The owner expects 180 voice/data outlets on this floor initially, with a build-out to 300. The room currently has a single 20 A convenience circuit and no dedicated HVAC. The building has a second floor served by a separate TR on the same riser. The owner asks whether they can 'share' this TR with the floor above to save space.
1. Assess the room against BICSI/TIA telecom room requirements and identify the deficiencies.
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Key deficiencies:
- Size: TIA-569/BICSI guidance ties TR size to served area. For a floor up to ~1,000 m² a small TR may suffice, but 2,400 m² with 300 outlets needs a larger room - BICSI guidance generally calls for roughly 3.3 m² (35 ft²) or more for larger floors, with room for racks, cable management, and future growth. A 7.2 m² room for 300 outlets is tight at best.
- Door: must open outward (into the corridor), be at least 900 mm wide and 2.0 m high, and swing clear of racks. An inward-opening door is a code/life-safety and access problem.
- Power: a single 20 A circuit is grossly inadequate. Provide dedicated circuits - typically at least two 20 A duplex receptacles on separate circuits, plus convenience outlets, and ideally a UPS-backed circuit for the active equipment.
- HVAC: no dedicated cooling. TRs need dedicated environmental control (typically 18–24 °C, ~30–55% RH) with positive pressure; sharing building HVAC is not acceptable for a room with active equipment.
- Ceiling height / cable entry: 2.7 m finished ceiling is workable but confirm ladder rack and overhead cable entry clearances.
- Shared wall with electrical closet: acceptable only with separation; keep power panels out of the TR and maintain EMI separation.
- Fire suppression / firestopping: confirm the room's rated walls and penetrations are firestopped.
- Grounding: a telecom ground bar (TGB) bonded to the building ground is required.
2. The owner wants to share this TR with the floor above. How do you respond?
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Decline the shared-TR concept for these floors. Each floor should be served by its own TR when the floor area and outlet count justify it - a single TR serving two 2,400 m² floors would put the upper floor's horizontal runs well beyond the 90 m permanent-link limit and create a single point of failure for both floors.
Explain the trade-offs concretely: from this TR to the far corner of the floor above, the route would exceed the horizontal cabling distance, forcing a second TR anyway. A shared TR also concentrates all cross-connect and active equipment in one room, so one HVAC or power failure takes down both floors.
Offer alternatives: (a) a properly sized TR on each floor connected by backbone fiber on the riser; (b) if space is truly constrained, a smaller satellite TR/consolidation point on the upper floor, but only within the horizontal distance budget. Put the recommendation in writing with the distance calculations so the owner can see the basis.
3. What design changes do you recommend before construction documents are finalized?
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- Enlarge the room - target a size consistent with 300 outlets and growth, with wall space for at least two racks and cable management.
- Re-hang the door to open outward, 900 mm minimum, with hardware that allows the door to be secured.
- Add power: two dedicated 20 A circuits on separate phases plus a UPS-backed circuit; coordinate with the electrical engineer.
- Add dedicated HVAC with a thermostat and humidity control; specify positive pressure and no return-air sharing with the office.
- Add a TGB bonded to the building ground, and coordinate bonding of racks, ladder rack, and cable shields.
- Confirm fire-rated walls and firestopping at all penetrations, including the shared wall with the electrical closet.
- Document the riser backbone to the upper-floor TR and confirm fiber counts and pathway.
- Issue an RFI to the architect with these items so they are resolved in the CDs, not in the field.