Estimate cooling capacity requirements for data centres and critical facilities.
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Cooling load is the amount of heat a data centre's cooling system must remove to keep IT equipment within safe operating temperatures. In a data hall almost all electrical power drawn by servers, storage and networking is converted to heat, so the cooling load closely tracks the IT load. This estimator sizes peak cooling capacity from rack count, rack power density, containment and redundancy, following the principles in CIBSE Guide B2, the ASHRAE TC 9.9 thermal guidelines for data processing environments, and ASHRAE 90.1 for system efficiency.
Take 20 racks at an average 8 kW per rack. The IT load is 20 x 8 = 160 kW, and because nearly all of that becomes heat the base cooling duty is about 160 kW. Add N+1 redundancy on a system built from four units and you install roughly five units of capacity (about 200 kW) so one can fail or be serviced without loss of cooling. Add cold-aisle containment and the same duty is met with less fan and chiller energy, lowering the facility PUE.
| Approach | Typical rack density | Where it fits |
|---|---|---|
| CRAC / CRAH (perimeter air) | up to about 8 kW | Legacy and lower-density halls |
| In-row cooling | about 8 to 20 kW | Modern enterprise and colocation |
| Rear-door heat exchanger | about 15 to 40 kW | High-density retrofit, low disruption |
| Direct liquid cooling | about 40 to 100 kW plus | AI and HPC racks |
| Immersion cooling | very high | Dense AI clusters, harsh ambient edge |
Higher-density racks driven by AI and HPC workloads are pushing sites beyond the limits of perimeter air, which is why liquid approaches are now mainstream in new design.
Early sizing for a new data hall or a densification of an existing one, before a full CIBSE load study.
Check cooling capacity when moving to higher rack densities or introducing AI and HPC racks.
Test a vendor's proposed cooling capacity and redundancy against your actual IT load.
For a data hall the cooling load is taken as approximately equal to the IT electrical load, since nearly all power drawn by IT equipment is dissipated as heat. The IT load is the number of racks multiplied by the average rack power density. Installed cooling capacity is then set above this peak duty to allow for redundancy, following CIBSE Guide B2 and ASHRAE TC 9.9 practice.
Perimeter air (CRAC or CRAH) is generally practical up to about 8 kW per rack. Between roughly 8 and 20 kW, in-row cooling or rear-door heat exchangers are used. Above about 40 kW per rack, typical of AI and HPC deployments, direct liquid or immersion cooling is required.
Redundancy sets how much spare cooling plant is installed so the design duty is still met during a failure or maintenance. N+1 adds one extra unit beyond the number needed, N+2 adds two, and 2N provides a fully duplicated system. More redundancy raises the installed capacity above the raw peak load.
Yes. The cooling load itself is fixed by the IT heat, but how efficiently it is removed drives energy use. Containment, higher supply air temperatures toward the ASHRAE A2 range, free-cooling economisers and liquid cooling all reduce the energy the cooling system consumes, which lowers PUE.
Yes. NOVTRIQ thermal engineers deliver validated cooling load assessments, containment and airflow design, liquid-cooling feasibility and full CIBSE-based studies for procurement and design. This estimator is an indicative first cut; a certified study accounts for the specific climate, layout and equipment.