Cooling
Water classes and NVIDIA's 45 deg C
ASHRAE classes facility water by maximum supply temperature: W17, W27, W32, W40, W45 and W+ above 45. NVIDIA's MGX specification for GB200, GB300 and Vera Rubin states 45 deg C inlet, a W45 design, with water returning near 55 deg C. One third-party analysis suggests some Vera Rubin configurations may return nearer 65 deg C.
Source: https://www.supercomputing.news/emerging/nvidia-45c-warm-water-cooling-mgx-data-center Checked 2026-09-18
| Figure | Value | Source |
|---|---|---|
| NVIDIA inlet | 45 deg C (113 deg F) | https://blogs.nvidia.com/blog/liquid-cooling-ai-factories/ Upgraded from a press write-up to NVIDIA's own blog post ('Hotter Than a Hot Tub: The 45C Breakthrough to Cool AI's Biggest Machines'), which directly states MGX racks run 'up to 45 degrees Celsius, or 113 degrees Fahrenheit' inlet. |
| Return | about 55 deg C per NVIDIA | https://blogs.nvidia.com/blog/liquid-cooling-ai-factories/ NVIDIA's own blog states the coolant entering a fully liquid-cooled chip at 45 deg C exits at roughly 55 deg C (facility-water framing: 41 deg C in, ~55 deg C coolant out). |
| Third-party return estimate | up to about 65 deg C | https://www.supercomputing.news/emerging/nvidia-45c-warm-water-cooling-mgx-data-center unverified Confirmed by direct fetch: the supercomputing.news article states SemiAnalysis has modeled return temperatures approaching 65C in some Vera Rubin configurations; NVIDIA's published figure is the lower one. Article accurately reports the estimate, but it is still a press relay of SemiAnalysis, not SemiAnalysis's own page — stays unverified pending a direct SemiAnalysis source. |