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UPS Runtime for Network Closet / IDF
When a **closet UPS** fails, **Wi-Fi**, **VoIP**, and **security VLANs** drop even if the data center stays up. Size for **switch + router + firewall** watts and **PoE budget**, not switch nameplate alone.
Who this scenario is for
Best for: IT and facilities teams protecting **IDF/MDF closets**, **PoE access switches**, and **uplink routers** in branch buildings.
Not ideal for: Whole-building backup, **large data halls**, or closets where **generator-backed** panel already covers the feed without bridge gaps.
Quick answer
Screen **0.35 kW** (switch + router + partial PoE) on **1.5 kVA** with **48 V / 100 Ah**—often **45–90 minutes** at light load; add watts per powered AP/camera port.
Key variables
- PoE load budget: Sum **802.3af/at** draw for powered devices; budget **20% headroom** for future APs.
- Closet temperature: Small closets **heat-soak** UPS batteries—derate minutes in summer or add ventilation.
- Dual uplink vs. single UPS: Single UPS protects **local closet** only—WAN outage still kills remote access unless **out-of-band** path exists.
Example: 24-port PoE switch + router
**0.35 kW** measured on **1.5 kVA** with **48 V / 100 Ah** often screens **about an hour** of runtime—verify after adding cameras or APs on PoE.
Next steps — tools
- UPS Runtime Calculator — minutes at your kW, V, and Ah.
- UPS Load Calculator — roll up devices before runtime.
- UPS Battery Calculator — Ah for a target minute goal.
- UPS Capacity Calculator — required kVA with PF and margin.
- How long will UPS last? — guided entry across the UPS tool chain.
Assumptions and disclaimer
Figures on this page are planning estimates using typical efficiency (~0.8) and safety factor (~0.7). Battery age, temperature, discharge rate, and UPS topology change real minutes. Confirm procurement with manufacturer runtime charts and your licensed engineer where required.
Frequently asked questions
How long should an IDF UPS run?
Enough for **graceful shutdown** or until **generator/transfer** completes—often 30–60+ minutes at measured closet kW.
Should I include the core switch on branch UPS?
Only if that closet is the **only** feed—core tiers usually have **data-center** UPS or redundant paths.
Is a rack-mount UPS required?
Not always—**tower UPS** works in small closets if **ventilation** and **weight** fit; document **battery replacement** access.
Often planned together
- Server rack — When the closet grows into a rack room
- CCTV — PoE cameras on the same switch
Related UPS scenarios
All scenario guides · How long will UPS last? · UPS Runtime Calculator · Runtime calculation guide