ASHRAE
The engineering society whose thermal guidelines define the temperature and humidity envelopes for IT equipment.
Current numbers
Addendum b approved 27 February 2026ASHRAE CDU test and rating boundary: external head and electrical inputs
G0-2019 / G1.1-2025 / Std 202-2024; G1.6P proposedASHRAE register: published process/HVAC&R references and proposed data-center guideline; freeze the project's adopted editions
W17–W45+ASHRAE liquid classes by max supply water temp (17/27/32/40/45 °C, plus W+); all share a 2 °C lower limit