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Server room and rack

Paste the list of servers, switches and patch panels to see how many racks to use, how much heat the room produces, how many cooling units to install and how many kVA the UPS needs.

Pre-sizing and estimating tool: results do not replace design, calculations or reports signed by a licensed professional, nor verification against the applicable codes and standards.

Pre-sizing
Equipment
See what was read

Use typical measured or vendor-stated draw, not power supply nameplate rating, which is often 1.5 to 2 times higher. Patch panels and cable managers go in at 0 W.

Racks
Heat load and cooling
Power supply
—Racks needed
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Space and power per rack

Bars: used and free U in each rack, with the suggested layout. Points: rack power.

Tap the chart to see the values.

Heat load breakdown

Heat the cooling must remove from the room, by source.

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Suggested rack layout

Equipment split to balance power across racks while respecting free U.

Next step

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Size the UPS feeder cable →Work out the UPS battery run time →

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Method, assumptions and references

Equations used

Space: U = Σ height × quantity; racks ≥ max[U × (1 + allowance) ÷ U_rack ; P ÷ P_max per rack], with a layout that balances power
Heat: Q = [P_IT + P_IT (1/η − 1) + area × lighting + 120 W × people + U × A × ΔT] × (1 + safety)
Conversions: 1 W = 3.412 Btu/h; 1 ton = 12,000 Btu/h = 3.517 kW; units = ⌈Q ÷ capacity⌉ + 1 (N+1)
Airflow: V = P_IT ÷ (ρ · cp · ΔT), ρ = 1.2 kg/m³, cp = 1,006 J/(kg·K)
Electrical: I = P ÷ (√3 · V · PF) three-phase or P ÷ (V · PF) single-phase; UPS = P ÷ PF × (1 + headroom), rounded up to a standard size

Assumptions and limits

  • All IT electrical power becomes sensible heat in the room; the UPS sits inside the room. People: 120 W each (sensible + latent, light work).
  • Envelope load is a steady-state estimate without solar gain; rooms with windows or exposed roofs need a full ASHRAE load calculation.
  • ASHRAE ranges from the Thermal Guidelines 4th edition (class A1); the 5th edition (2021) allows up to 70% RH in low-pollutant rooms.

Standards and technical documents

  • ANSI/TIA-942-B:2017: Telecommunications Infrastructure Standard for Data Centers
  • ASHRAE TC 9.9: Thermal Guidelines for Data Processing Environments, 4th ed. (2015) and 5th ed. (2021)
  • ABNT NBR 14565:2019: Cabeamento estruturado para edifícios comerciais
  • EN 50600-2-3: Data centre facilities and infrastructures — Environmental control
  • EIA-310-E / IEC 60297-3-100: 19-inch rack dimensions

U.S. regulations

  • NFPA 75: Standard for the Fire Protection of Information Technology Equipment
  • NFPA 70 (NEC) Article 645: Information Technology Equipment
  • OSHA 29 CFR 1910 Subpart S: electrical safety
  • ASHRAE 90.4: Energy Standard for Data Centers

Frequently asked questions

How many Btu of cooling does a server room need?

Add up equipment power in watts and multiply by 3.412: 10 kW of IT gives about 34,100 Btu/h, or 2.8 tons. Add UPS losses, lighting, people and walls, plus a 10% margin. With N+1 redundancy, install one extra unit.

How much equipment fits in a 42U rack?

Up to 42 one-U devices, but common practice leaves 20% to 30% free for growth and cable managers. With 30% allowance about 32 usable U remain.

What temperature should a server room run at?

ASHRAE recommends 64.4 to 80.6 °F (18 to 27 °C) at the equipment inlet, measured at the rack front, not at the cooling unit return. Running near 75 to 80 °F saves energy while staying in the recommended range.

How do I size the room UPS?

Divide equipment power by the power factor and add 25% headroom. For 9.85 kW at PF 0.9 that is 13.7 kVA, or a 15 kVA UPS.