How the cooling load is calculated
In a server room nearly all electrical energy drawn by equipment turns into heat, so IT power is the starting point; heat from other sources is added on top. The method follows the simplified approach common in datacenter design guides (including Schneider/APC white papers).
Q_IT = P_IT (≈100% of electrical power)
Q_UPS = P_IT × (1/η_UPS − 1) (only if UPS is in the room)
Q_light = area × W/m²
Q_people = people × 100 W
Q_windows = window_m² × solar gain (0 / 100 / 250 / 450 W/m²)
Q_envelope = area × 20 W/m² (exterior wall/roof)
Q_total = Σ Q Q_design = Q_total × (1 + margin)
BTU/h = W × 3.412 tons = BTU/h ÷ 12,000
N+1 layout
The tool finds the smallest standard unit size (3.5–100 kW) for which at most three units carry the design load, then adds one standby unit. If any unit fails or is serviced, the rest still carry the full load.
Airflow
Airflow [m³/h] = Q [W] × 3.6 ÷ (ρ 1.2 kg/m³ × cp 1.005 kJ/kg·K × ΔT)
A smaller supply/return ΔT means more air is needed — which is why hot/cold aisle containment improves cooling efficiency.
Assumptions & limits
- People: 100 W each (light activity).
- Window solar gain varies hugely with orientation and season; values are conservative summer peaks for a Tehran-like climate.
- Fresh air, infiltration and dehumidification are not included; a final design needs an HVAC engineer.
- Rated AC capacity drops at high outdoor temperatures; check the manufacturer’s capacity tables at real conditions.