2023 ASHRAE Handbook: HVAC Applications, Chapter 20, Data Centers and Telecommunication Facilities

Overview

Chapter 20, in its SI edition, discusses data-center cooling approaches and includes the classes of ASHRAE Thermal Guidelines for Data Processing Environments (fifth edition, 2021). The environmental table combines dry-bulb temperature, moisture and altitude conditions, so looking at temperature alone does not tell you whether a server inlet is inside the envelope. A one-line requirement such as a maximum inlet temperature is therefore not enough; moisture and dew point are assessed in the same table.

Table 1 defines each air-cooled equipment class using temperature, noncondensing humidity, dew point and elevation limits. Its footnotes require an altitude adjustment to the maximum dry-bulb temperature: at a high site the permitted upper temperature is lower than at sea level. All conditions must be satisfied together. The same equipment class can therefore have two different maximum temperatures depending on the site; the class name alone is not enough information.

The copyrighted handbook is linked, not redistributed. The document defines the allowable envelope; it does not recommend operating continuously at the boundary of that envelope. A designer should retain the class and altitude assumptions on record and not reduce the environment to a single temperature threshold. Because the chapter reproduces the 2021 classes, it should be read together with the fifth-edition Thermal Guidelines, where the detailed class tables sit.

Key points

1. The chapter reproduces the 2021 thermal equipment classes.
2. Table 1 defines each air-cooled class by temperature, noncondensing humidity, dew point and elevation limits.
3. Footnotes require an altitude adjustment to maximum dry-bulb temperature.
4. Temperature alone is insufficient to evaluate the inlet envelope.
5. Related document: ASHRAE Thermal Guidelines for Data Processing Environments, fifth edition (2021).

Using it in design

• Evaluate all applicable inlet conditions (temperature, moisture, dew point, altitude) together.
• Retain class and altitude assumptions in the design record.
• Do not present passing an allowable-envelope check as a recommendation to run continuously at its boundary.

Who should read it

Mechanical designers setting server inlet conditions and the cooling design envelope.

Related standards

• ASHRAE Thermal Guidelines for Data Processing Environments, fifth edition (2021)

Publication details

Authors

ASHRAE

Publisher

ASHRAE

Year

2023

Document number

2023 HVAC Applications, Chapter 20 (SI)

Document language

English

Source type

Standard

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation