# Cooling method picker by rack kW

Select a cooling approach by your target rack density (kW per rack). Thresholds based on published vendor data, ASHRAE classes, and industry deployments.

Use the tool on the [web page](https://liquidcooling.fyi/tools/cooling-method-picker). It works without JavaScript.

## How to use it

1. Enter target rack density.
2. Enter is this a brownfield retrofit?.
3. Choose pue target.
4. Read the result.

## How it works

Density thresholds based on published vendor specifications and deployments: NVIDIA GB200 NVL72 at ~140 kW/rack (TrendForce, 2024; NVIDIA, 2026); Schneider Electric and NVIDIA Vera Rubin NVL72 reference designs up to 227 kW/rack (Schneider Electric AI Factory Reference Designs 112/113, https://www.se.com/ww/en/work/solutions/ai-factory/reference-designs/); AMD Helios rack-scale reference (Mordor Intelligence, 2026); RDHx deployments up to 75 kW (Mordor Intelligence, 2026).

Air cooling limit of ~30 kW/rack reflects practical containment and fan power limits. Uptime Institute 2026 survey notes more operators reporting peak densities ≥30 kW for AI workloads (Mordor Intelligence, 2026).

W-class recommendations follow ASHRAE TC 9.9 Thermal Guidelines, 5th Edition (2021): W27-W32 enables dry cooler free cooling in most climates; W32-W45 for hot climates or maximum density.

PUE targets drive the rules: air cooling typically 1.3-1.6; RDHx 1.15-1.30; direct-to-chip 1.05-1.15; immersion 1.01-1.08 (Wikipedia PUE, 2026; industry reported values). A ≤1.05 target routes to two-phase immersion or the best end of direct-to-chip, ≤1.10 to direct-to-chip or two-phase, and any stated target rules out air.

> Guidance only. Final cooling selection requires vendor consultation, OEM warranty confirmation, facility constraints analysis, and fluid qualification. This tool does not replace engineering design.

## Questions

### Can I use air cooling at 50 kW/rack?

Air cooling with advanced containment can reach 40-50 kW/rack, but liquid cooling is more reliable and efficient above 30 kW. Uptime Institute's 2026 survey links rising peak densities to AI workloads (Mordor Intelligence, 2026).

### What is the density limit for rear-door heat exchangers?

RDHx typically handles 30-75 kW/rack, limited by air-side heat transfer. They are best for retrofit where server modification is not feasible. NorthC deployed RDHx at Münchenstein without downtime (Mordor Intelligence, 2026).

### When should I choose immersion over direct-to-chip?

Choose two-phase immersion for maximum density (>100 kW/rack) and best PUE (1.01-1.05). Choose single-phase immersion if you prefer hydrocarbon fluids (Shell S3 X, Intel certified). Direct-to-chip has broader OEM warranty support and is the NVIDIA/AMD reference design choice.