Cooling systems: CRAC, CRAH, chilled water and economizers
Follow the heat from the server to the outdoors through DX and chilled-water systems, read cooling-unit data, apply the ASHRAE recommended and allowable ranges at the level the guidelines state them, understand economizers, and know your part in a loss-of-cooling plan.
- Level
- Intermediate
- Length
- About 55 minutes
- Contents
- 3 lessons · 1 video · final exam
- Status
- Published · updated 3 Oct 2026
Skills you'll practise
- Trace the heat path from IT equipment to outdoors for DX (CRAC) and chilled-water (CRAH) systems, and name each component's job
- Apply the ASHRAE recommended and allowable inlet ranges to readings and explain what each range is for
- Explain how air-side and water-side economizers save energy and what stops them running
- Read cooling-unit and BMS data to tell a unit, plant or control problem apart, and escalate instead of changing setpoints
- Describe what a loss-of-cooling contingency plan contains and who may decide to shut down IT equipment
Course outline
- 1.Data center cooling: from the server to the outdoorsVideo · 2 min
- 2.Where the heat goes: DX and chilled-water systemsLesson · 18 min
- 3.ASHRAE ranges: recommended and allowableLesson · 17 min
- 4.Economizers, controls and losing coolingLesson · 18 min
- 5.Cooling systems: CRAC, CRAH, chilled water and economizers: knowledge checkKnowledge check · 18 questions
- 6.Cooling systems: CRAC, CRAH, chilled water and economizers: practical exerciseKnowledge check · 1 question
- 7.Chiller plant trip on a hot afternoonScenario
- 8.Final exam9 questions · passing it completes the course, so people who already know the material can test out
Sources it draws on
The lessons and questions are written from these references, so learners can go back to the original.
- U.S. DOE Federal Energy Management Program: Best Practices Guide for Energy-Efficient Data Center Design (2024), incl. ASHRAE 2021 thermal guideline table, cooling, electrical and metrics sections
- ASHRAE TC 9.9: Data Center Power Equipment Thermal Guidelines and Best Practices (2016), incl. the 2015 thermal guideline table and notes, power distribution chain, RPPs and busways
- ASHRAE TC 9.9: Data Center Cooling Resiliency brief (2021), quoting FM Global Data Sheet 5-32 on loss-of-cooling contingency plans and HVAC alarms
- ASHRAE TC 9.9: Thermal Guidelines for Data Processing Environments, 5th edition (2021) (check the current edition and your equipment's class)
See it with your own jobs and topics
Tell us about your team and we'll walk you through setup, from choosing jobs to your first skills check.