TR Sizing and Cooling in a Dense Wireless Deployment
A university is building a new 12,000 m² library. The design includes a main cross-connect (MC) in the basement and one TR per floor serving approximately 240 outlets each. The owner wants Wi-Fi 6E coverage everywhere and has asked that each TR also house the floor's wireless LAN controllers, PoE switches, and a small UPS. The architect has allocated a 2.4 m × 3.0 m closet per floor with a single 0.9 m door, no dedicated HVAC, and shared access with housekeeping storage. Electrical is a single 20 A circuit. The project manager wants to value-engineer by removing the UPS and using the housekeeping space for cleaning supplies.
1. Identify the deficiencies in the allocated TR and what the design must require.
Read the worked answer
Deficiencies include: size likely inadequate once racks, clearance, and growth are considered; a single 0.9 m door limits equipment movement and may not meet egress/clearance needs; no dedicated HVAC means heat rejection is unmanaged; shared use with housekeeping introduces dust, moisture, and security risk; a single 20 A circuit is insufficient for switches, PoE load, and UPS. The design must require dedicated environmental control (temperature and humidity within equipment ratings), adequate power (multiple circuits, dedicated panels where possible), proper door sizing and swing, and exclusive use of the space. These are design requirements, not options to be traded away.
2. Estimate the heat load concern and explain why removing the UPS is a poor value-engineering choice.
Read the worked answer
PoE switches delivering power to access points and devices dissipate heat in the TR, and the UPS adds both heat and the function of ride-through during outages. Without dedicated cooling, temperatures will rise above equipment ratings, causing thermal shutdowns and reduced equipment life. The UPS is not decorative: it protects the network and wireless coverage during short outages and supports orderly shutdown. Removing it shifts risk to the owner. A better value-engineering approach is to right-size the UPS and cooling rather than eliminate them, and to document the lifecycle cost of failures.
3. The PM asks you to sign off on the reduced scope. What is your professional response?
Read the worked answer
Decline to sign off on a design that omits required environmental and power provisions. Provide a written technical basis: equipment operating envelopes, calculated heat load, and the operational impact of shared storage and no UPS. Offer alternatives that meet budget (e.g., right-sized split system, smaller UPS, consolidated TR if distance permits) and escalate the decision to the owner with the risks documented. Signing off would transfer unbudgeted risk to the owner and compromise the design.