Design rules for HVAC & Ventilation

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HVAC & Ventilation

Cooling load: TR = BTU/h / 12,000 = kW / 3.517
Thumb rule (comfort): 1 TR per 100–120 ft² (9–11 m²)
Air flow from air changes: CFM = room volume (ft³) x ACH / 60; m³/h = volume (m³) x ACH
Duct area: A = Q / v (v = 6–8 m/s mains, 3–5 m/s branches)
Condenser water: ≈ 3 USGPM per TR; chilled water ≈ 2.4 USGPM per TR (10°F ΔT)
Pressurisation leakage: Q = Cd·A·√(2ΔP/ρ), typically 50 Pa across stair doors

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Standards cited by number for reference; verify designs with a qualified engineer.