CRAC Units (Computer Room Air Conditioning)

IT equipment runs around the clock. Data center precision cooling must operate continuously, 365 days a year, without interruption.

Servers need stable inlet temperatures. Too much humidity risks condensation, while too little increases static electricity. CRAC temperature control and CRAC humidity control keep both within safe limits.

IT equipment produces almost entirely sensible heat. Precision units are designed with a high sensible heat ratio to remove this heat efficiently.

Cooling failures can cause overheating and outages within minutes. Precision cooling systems include redundancy, standby changeover, and alarms to protect critical operations.

Scroll compressors provide reliable cooling. A CRAC inverter compressor varies capacity to match load for better efficiency.

A high-efficiency coil designed for high sensible cooling removes heat from the room air.

EC fans offer high airflow, low energy use, and variable speed control.

Filters keep dust away from IT equipment and the evaporator coil.

An electrode or infrared humidifier maintains the required humidity level.

Reheat elements maintain temperature during dehumidification.

The EEV precisely controls refrigerant flow for stable, efficient operation.

Temperature and humidity sensors feed the controller, which manages operation, alarms, and communication.

The CRAC unit condenser, or a dry cooler, rejects heat to the outdoor air.

A downflow CRAC unit draws warm air from the top and discharges cool air downward into a raised floor. It is the most common arrangement for raised floor CRAC units and underfloor data center cooling.

An upflow CRAC unit draws air from the bottom or front and discharges it upward into ducts or a ceiling plenum. It suits rooms without a raised floor.

These units discharge air horizontally at low velocity into the room. They suit small server rooms and telecom rooms.

In-row units sit between server racks and cool air right at the source. They are ideal for high density data center cooling.

Compact ceiling-mounted precision units save floor space in small server and network rooms.

An air cooled CRAC unit, or air cooled DX CRAC, connects to an outdoor condenser through refrigerant piping. This split CRAC system with an outdoor condenser is the most common type.

A water cooled CRAC unit, or water cooled DX CRAC, rejects heat to condenser water from a cooling tower or building water loop.

A glycol cooled CRAC unit uses a glycol loop and outdoor dry cooler, allowing longer distances between indoor and outdoor units.

Dual cooling units combine DX and chilled water coils, with either one acting as the main cooling source and the other as backup.

CRAC free cooling uses cool outdoor air or glycol to reduce compressor operation when outdoor conditions allow.

ASHRAE TC 9.9 publishes widely followed thermal guidelines for data processing environments, defining recommended and allowable ranges for IT equipment.

For most IT equipment, the recommended server inlet temperature range is 18°C to 27°C. Humidity is managed within a recommended dew point range and a maximum relative humidity of about 60%. Always check the latest guidelines and equipment manufacturer requirements.

The CRAC sensible heat ratio shows how much of the unit's capacity goes into sensible cooling. For data centers, a high CRAC sensible cooling capacity is essential.

CRAC unit sizing starts with the total IT load in kW, plus lighting, UPS losses, people, and building heat gains.

Airflow is selected based on the temperature rise across the IT equipment, typically around 120–160 CFM per kW depending on design delta-T.

Room dimensions, rack count, and kW per rack decide the number, type, and placement of units.

N+1 CRAC redundancy adds one standby unit beyond what is required. 2N provides a fully duplicated system for maximum reliability.

Racks are arranged so cold air enters from the front and hot air exits from the back into separate aisles, which is the foundation of hot aisle cold aisle cooling.

Floor height, tile placement, and open area are planned for even airflow to every rack.

A clear return air path, often through a ceiling plenum, brings hot air back to the units without mixing with cold air.

Enclosing the cold aisle keeps cool air in front of the racks and prevents mixing with hot air.

Enclosing the hot aisle captures exhaust air and returns it directly to the cooling units.

Blanking panels in empty rack spaces and sealed floor cut-outs prevent air bypass and recirculation.

Good airflow management, correct tile placement, and containment eliminate hot spots in server racks.

Variable speed CRAC units, with EC fans and inverter compressors, match cooling output to IT load and reduce energy use significantly.

Free cooling reduces compressor hours when outdoor conditions allow.

Operating at higher CRAC supply air temperatures within recommended limits improves efficiency.

Efficient CRAC units, containment, and smart controls lower cooling energy and improve Power Usage Effectiveness (PUE). An energy efficient CRAC unit for a data center pays back through lower operating costs.

Controllers manage temperature, humidity, fan speed, compressor staging, alarms, and event logs.

Units rotate duty to equalise run hours, and standby units start automatically if a running unit fails.

CRAC BMS integration and CRAC DCIM integration through SNMP, CRAC Modbus, or CRAC BACnet connect units to building and data center management systems.

CRAC remote monitoring sends alerts by email, SMS, or dashboards so issues are addressed immediately.

Leak detection cables under raised floors alert operators to water from drains, humidifiers, or pipes.

Stable conditions protect IT equipment and extend its life.

Designed specifically for the sensible heat produced by IT equipment.

Industrial-grade components are built for continuous operation.

Lead-lag and standby features prevent cooling interruptions.

Precision cooling reduces the risk of hardware failure and downtime.

DX CRAC units work without a central chiller, which is ideal for standalone server rooms.

Precision units cost more upfront, but they deliver far greater reliability and control.

In large facilities, chilled water CRAH units may be more efficient.

The distance and height between indoor units and outdoor condensers are limited.

Perimeter units occupy space inside the data hall.

High airflow units create noise inside the room, which is normal for data centers.

Compress India designs each installation to balance reliability, efficiency, and space.

A CRAC unit for data centers provides reliable perimeter or in-row cooling for enterprise and colocation facilities.

A CRAC unit for server rooms delivers precise, 24/7 cooling for company IT infrastructure.

A CRAC unit for telecom rooms protects network and switching equipment.

Precision cooling protects UPS systems and extends battery life.

Control rooms in plants, utilities, and transport hubs need stable conditions for equipment and operators.

Labs and test rooms need tight temperature and humidity control.

Medical imaging equipment rooms require precise, reliable cooling.

Banks rely on precision cooling to protect critical financial systems.

Vertiv CRAC units, formerly known as Liebert CRAC units, are widely used in data centers and server rooms across India.

Schneider Electric's Uniflair range offers perimeter and in-row precision cooling solutions.

STULZ CRAC units are known for precision air conditioning and close control solutions for data centers.

Rittal offers rack-based and room-level cooling solutions for IT environments.

Blue Star offers precision air conditioners for data centers and server rooms in India.

Mitsubishi Electric, through its Climaveneta range, offers precision cooling units for mission-critical applications.

Other options include Airedale and Daikin precision cooling units. Compress India recommends the best-fit brand based on your requirements.

Scheduled quarterly visits cover inspections, cleaning, testing, and performance checks.

Filters are replaced regularly to maintain airflow and protect equipment.

Humidifier cylinders are inspected and replaced as they wear out.

Compressor current, pressures, and refrigerant charge are checked to prevent failures.

Outdoor condenser coils are cleaned to maintain heat rejection and prevent high-pressure trips.

Sensors are calibrated and controller settings verified for accurate control.

Our team provides round-the-clock support for critical cooling failures.

Causes: unit failure, blocked airflow, dirty filters, or increased IT load.

Solution: Check unit operation, clean filters, improve airflow, and review capacity.

Causes: dirty condenser, refrigerant leak, or fan failure.

Solution: Clean condensers, repair leaks, and check fans.

Causes: worn cylinders, poor water supply, or scaling.

Solution: Replace cylinders and check the water supply and drain.

Causes: blocked drains, humidifier overflow, or pipe leaks.

Solution: Clean drains, repair leaks, and test leak detection.

Causes: poor airflow management, missing blanking panels, or wrong tile placement.

Solution: Add containment and blanking panels, and rebalance tiles.

Causes: oversized units, control issues, or low load.

Solution: Adjust control settings, use inverter compressors, or rebalance units.

Causes: failed sensors or controller errors.

Solution: Recalibrate or replace sensors and update controllers.

Replacing old fans with EC fans cuts energy use and improves airflow control.

Ageing units can be replaced with modern, efficient precision units with better controls.

Hot or cold aisle containment improves cooling efficiency and removes hot spots.

Inverter CRAC units and free cooling options reduce energy consumption.

High-density areas can be upgraded with in-row cooling units.

Higher capacity units cost more. Inverter compressors, EC fans, free cooling, and dual cooling features add to the price but reduce operating costs.

Refrigerant piping, outdoor condensers, floor stands, drains, electrical work, and leak detection form part of the installed cost.

Brand, capacity, number of units, redundancy level, containment, controls, and site conditions all affect the final price.

Share your IT load and room layout with Compress India to receive an accurate CRAC unit quotation.