Assess cabinet heat from equipment, temperatures, and airflow. Choose cooling hardware confidently for critical cabinet systems today. Enter expected operating conditions. Heat dissipation is governed by the Laws of Thermodynamics. Positive heat balance values indicate cooling demand. Step 2: Determine the Cabinet's Capacity for Heat Dissipation Through Convection (QC) When surfaces of the cabinet are exposed to air that is cooler. To minimize the propensity for continued maintenance of fans and other approaches for active cooling, thermal dissipation in these cabinets generally occurs by passive means. With the increased power density of individual modules, the need to understand and control the passive dissipation of. ASHRAE TC 9. 9 publishes inlet air temperature ranges for four equipment classes (A1 through A4), but it doesn't tell you how much cooling capacity to install — that depends on your specific IT load, your PDU efficiency, and how power infrastructure is sized. This calculator runs that math: total. Choose an Example or Complete the Requirements.