Thermal Guidelines for Data Processing Environments, 5th ed. (ASHRAE Datacom Series Book 1)
ASHRAE · ASHRAE TC 9.9
ASHRAE TC 9.9's flagship book defining environmental classes for air- and liquid-cooled IT; the 5th edition added pollutant-dependent humidity limits and the high-density class H1.
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Overview
Thermal Guidelines for Data Processing Environments is Book 1 of the ASHRAE TC 9.9 Datacom Series (product code 90579). The committee first published it in 2004, and the fifth edition appeared in 2021. At the time of the 2019 Handbook, Book 1 was still the 4th edition (2015). It is regarded as the industry's core thermal reference, defining environmental classes for air- and liquid-cooled IT equipment.
The 5th edition brought two notable changes. The first is pollutant-dependent humidity limits, allowing relative humidity of up to 70% on condition that corrosive gas levels are low. The second is a new high-density server class, H1. For H1 the recommended temperature range is 18-22 C and the allowable range is 15-25 C, as given in the TC 9.9 Reference Card.
The 2024 catalogue lists it at $83, or $62 for ASHRAE members. This page was prepared without reading the book itself, from catalogue, Handbook and trade-press descriptions. The link points to the official ASHRAE errata for product 90579. Readers should consult the publisher for the current edition and corrections.
Key points
- Datacom Series Book 1, 5th edition, product code 90579.
- First published by TC 9.9 in 2004; fifth edition in 2021.
- At the 2019 Handbook, Book 1 was the 4th edition (2015).
- 5th edition allows RH up to 70% conditional on low corrosive gases.
- New high-density server class H1 added.
- H1: recommended 18-22 C, allowable 15-25 C.
Using it in design
- Primary reference for the thermal-class data used by the rule engine; record the edition (5th) per project.
- For high-density liquid-cooled IT, compare the H1 ranges (recommended 18-22 C, allowable 15-25 C) with the design temperature assumptions.
- Verify corrosive-gas levels on site before raising relative humidity towards 70%.
- Read it together with ANSI/ASHRAE Standard 90.4 for efficiency calculations.
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Who should read it
Cooling and mechanical design engineers and operations teams who set environmental conditions for IT equipment.
Related standards
- ANSI/ASHRAE Standard 90.4
Publication details
- Authors
- ASHRAE TC 9.9
- Publisher
- ASHRAE
- Year
- 2021
- Document number
- Datacom Series Book 1 (product 90579)
- Document language
- English
- Source type
- Standard
- Access
- Citation only
- Licence
- Copyright retained; citation only — the publisher’s terms apply to the original document
Original licence note
Copyrighted ASHRAE book sold via ASHRAE Bookstore (and TC 9.9 Datacom Encyclopedia subscription). Not read; metadata from ASHRAE catalogue / Handbook descriptions only. Citation only.
Citation
ASHRAE TC 9.9 (2021). Thermal Guidelines for Data Processing Environments, 5th ed. (ASHRAE Datacom Series Book 1). ASHRAE. Datacom Series Book 1 (product 90579). https://www.ashrae.org/file%20library/technical%20resources/publication%20errata%20and%20updates/90579_errata.pdf
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