Mechanical engineers need the PDF to design cooling systems. Because 90.4 allows "performance-based" compliance, engineers use the tables in the PDF to simulate trade-offs (e.g., using a less efficient UPS if you install a highly efficient economizer-cooled CRAH).
The 2022 edition introduced several significant updates that reflect the latest technologies and industry best practices:
If one component misses the target, apply the standard's trade-off methodology to see if the other component compensates for the deficit.
+---------------------------------------+ | ASHRAE Standard 90.4 | +---------------------------------------+ | +------------------------+------------------------+ | | v v +---------------------------+ +---------------------------+ | Mechanical Systems (MLC) | | Electrical Systems (ELC) | +---------------------------+ +---------------------------+ * HVAC & Chillers | * UPS Energy Losses | * Fans & Pumps | * Distribution Systems | * Heat Rejection Equipment | * Backup Generators | +---------------------------+ +---------------------------+ The Evolution: Why Data Centers Needed 90.4 Over 90.1 ASHRAE Releases Revised Version of Data Center Standard
ASHRAE 90.4 uses a performance-based approach, focusing on two primary components rather than just the traditional Power Usage Effectiveness (PUE) metric: ashrae 90.4 pdf
This public link is valid for 7 days and shares a thread, including any personal information you added. This link or copies made by others cannot be deleted. If you share with third parties, their policies apply. Can’t copy the link right now. Try again later.
The screen flickered. The results window popped up.
[1]. Unlike standard commercial buildings, data centers have unique high-density cooling requirements and electrical loads that necessitate a specialized set of rules [2]. The Core Purpose of 90.4
ASHRAE provides read-only digital access to their standards for public reference. This is an excellent, free way to review the code. Mechanical engineers need the PDF to design cooling systems
By following the guidelines and requirements set out in ASHRAE 90.4, data center owners and operators can improve energy efficiency, reduce waste, and increase reliability.
The standard provides different ELC limits based on the facility's level of redundancy (e.g., whether it uses a single-feed system or a fully redundant, dual-path architecture). Compliance Paths: How to Achieve Certification
For a pure data center, 90.4 alone suffices. However, if your building contains office space, the office must comply with 90.1, while the data center complies with 90.4.
This path allows for engineering flexibility. If your cooling system (MLC) is exceptionally efficient, you are allowed a slightly less efficient electrical system (ELC), or vice versa. As long as the combined energy performance does not exceed the total allowed budget, the facility complies. The Performance Path Can’t copy the link right now
If you open the PDF, you will notice that 90.4 doesn't just give you a simple number. It forces you to use to calculate your IT load diversity.
While ASHRAE 90.4 uses calculations that look very similar to PUE, it .
If your calculated MLC ≤ the table allowance → You comply. If it exceeds → You must redesign (add economizers, higher efficiency fans, or liquid cooling).