The importance of ASHRAE TC 9.9

🔹 1. What ASHRAE TC 9.9 Is?

ASHRAE TC 9.9: Mission Critical Facilities, Data Centers, Technology Spaces and Electronic Equipmentis a technical committee within ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers).

It brings together experts from:

• IT hardware manufacturers (Dell, HP, IBM, Cisco)

• Facility and mechanical engineers

• Operators of hyperscale and colocation data centers

• Researchers and energy-efficiency organizations

Goal: Develop thermal guidelines and best practices to balance equipment reliability, energy efficiency, and sustainability in mission-critical environments.

🧠 2. Key Publications (by ASHRAE TC 9.9)

Title	Focus
Thermal Guidelines for Data Processing Environments	Defines allowable & recommended temperature/humidity ranges for IT equipment (foundation document).
Liquid Cooling Guidelines for Datacom Equipment Centers	Covers direct-to-chip, immersion, and hybrid liquid cooling systems.
Best Practices for Datacom Facility Energy Efficiency	Guides on optimizing power and cooling efficiency (including PUE and WUE).
High Density Data Center Design	Addresses air and liquid cooling for >20 kW/rack environments.
IT Equipment Power Trends and Cooling Applications	Predicts thermal and power evolution for next-gen servers (useful for AI and HPC).
Datacom Equipment Power Trends and Cooling Applications (6th Edition)	Latest version reflecting GPU and AI-era thermal requirements (2022–2023).

🌡️ 3. Environmental Classes (Thermal & Humidity)

The “Thermal Guidelines for Data Processing Environments” (currently 5th Edition) defines four key Environmental Classes (A1–A4) for air-cooled equipment and H1–H3 for liquid-cooled systems.

Air-Cooled Classes (Typical Ranges)

Class	Recommended Temp (°C)	Recommended RH (%)	Allowable Temp (°C)	Typical Use
A1	18–27	40–60	15–32	Enterprise / legacy data centers
A2	18–27	40–60	10–35	General IT environments
A3	18–27	40–60	5–40	Energy-efficient modern IT
A4	18–27	40–60	5–45	High-tolerance equipment

Liquid-Cooled Classes

Class	Coolant Inlet Temp (°C)	Typical Use
H1	17–45	Standard data centers
H2	2–60	HPC and AI workloads
H3	2–65	Extreme-density / immersion systems

Note: Modern HPC and AI racks (e.g., NVIDIA H100) often operate under H2/H3 conditions with liquid inlet temps around 30–40 °C to enable free cooling (chillerless operation).

⚙️ 4. Importance for Data Center Design

ASHRAE TC 9.9 provides industry-accepted design envelopes for:

• Temperature and humidity control

• Airflow and containment design

• Liquid loop management

• Instrumentation and monitoring

• Reliability vs energy trade-offs

It helps define:

• Setpoints for CRAH/CRAC or CDU systems.

• Free cooling strategies based on local climate.

• Equipment selection (servers, chillers, heat exchangers).

• Service Level Agreements (SLA) for uptime and hardware reliability.

🔄 5. Integration with Liquid Cooling

In recent years, TC 9.9 has added extensive sections on:

• Direct-to-chip cold plate design (ΔT limits, leak containment, dielectric fluids)

• Coolant quality standards (conductivity, corrosion inhibitors)

• Facility and IT loop isolation

• ASHRAE H1–H3 classification (as above)

• Energy recovery and water-side economization

It recognizes that air cooling alone is no longer viable beyond ~20–25 kW/rack in modern compute environments.

📊 6. Relationship to Other Standards

Standard	Connection
ISO/IEC 30134	Energy metrics (PUE, WUE, REF).
ANSI/TIA 942	Data center topology and Tier classification — ASHRAE TC 9.9 defines environmental parameters used within it.
IEC 62368 / UL	Safety and material compatibility for cooling fluids.
ASHRAE 90.4	Data center energy efficiency code; TC 9.9 data underpins compliance.