CRAH Units (Computer Room Air Handlers)

Large data halls with megawatts of IT load need cooling that scales easily. High capacity CRAH units deliver more cooling per unit than typical DX systems.

Central chiller plants with efficient chillers, variable flow, and free cooling generally deliver lower energy use per kW of cooling than many distributed DX units.

With compressors located in the central plant, CRAH units reduce noise, maintenance, and refrigerant inside the white space.

Chilled water systems integrate easily with free cooling chillers and economizers, reducing mechanical cooling hours.

The CRAH cooling coil is designed for high sensible cooling at the data center's chilled water temperatures.

An EC plug fan CRAH design, often configured as a CRAH fan array, delivers efficient, redundant airflow.

The CRAH air filter protects the coil and IT equipment from dust.

Two-way valves and PICVs support variable flow systems, while three-way valves maintain constant flow. A PICV for CRAH delivers stable control and simpler balancing.

These components maintain humidity within recommended limits.

A drain pan and condensate line remove any moisture from the coil.

Temperature, humidity, pressure, and flow sensors feed the controller for precise operation.

Leak detection cables under and around the unit alert operators to any water leakage.

A downflow CRAH unit supplies cool air into a raised floor, delivered through perforated tiles to the cold aisle. It is the most common raised floor CRAH unit and the standard for underfloor data center cooling.

An upflow CRAH unit discharges air upward into ducts or a ceiling plenum, which suits rooms without a raised floor.

These units supply air horizontally at low velocity, which suits non raised floor CRAH layouts.

In-row units sit between racks and cool air at the source, making them ideal for high density data center cooling.

Fan walls are large banks of fans and coils in a separate corridor, supplying very high airflow to large data halls, which is common in hyperscale designs.

Chilled water coils mounted on rack rear doors remove heat directly from the rack exhaust.

Standard units with one chilled water coil served by one circuit.

Two coils fed from separate chilled water circuits provide redundancy if one circuit fails.

These units combine a chilled water coil with a DX circuit, so the DX system can take over if chilled water is lost.

High temperature chilled water CRAH units are designed with larger coils to deliver full capacity at elevated water temperatures, improving chiller efficiency.

Modern data centers often use higher chilled water temperatures than comfort cooling systems, improving chiller efficiency and free cooling hours.

Free cooling chillers and water-side economizers use cool outdoor conditions to reduce compressor operation.

Redundant chillers and CRAH chilled water pumps keep cooling running during failures or maintenance.

Chilled water storage tanks keep cooling running for a short period during power interruptions, until chillers restart.

Dual-path or ring main piping allows maintenance or repair without interrupting cooling to the data hall.

ASHRAE TC 9.9 publishes widely followed thermal guidelines for data processing environments.

For most IT equipment, the recommended server inlet temperature range is 18°C to 27°C, with humidity controlled within recommended dew point limits and relative humidity of up to about 60%. Always check the latest guidelines and equipment requirements.

Data center loads are almost entirely sensible, so a high CRAH sensible cooling capacity is essential.

CRAH unit sizing starts with total IT load in kW, plus other heat gains in the room.

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

Supply and return temperatures are selected to balance coil size, chiller efficiency, and free cooling potential. Many modern designs use supply temperatures in the mid-teens °C or higher.

Coils are selected to deliver full capacity at the design water temperatures, since capacity falls as water temperature rises.

N+1 CRAH redundancy adds one extra unit beyond what is required, while 2N provides a fully duplicated system.

Racks are arranged in alternating hot and cold aisles for efficient hot aisle cold aisle cooling.

Floor height and tile layout are planned for even airflow to every rack.

Enclosing the cold aisle keeps cool air in front of the racks.

Enclosing the hot aisle captures exhaust air and returns it directly to the CRAH units, increasing CRAH return air temperature and coil efficiency.

Blanking panels and sealed floor openings prevent air bypass and recirculation.

Containment, correct tile placement, and rack inlet monitoring eliminate hot spots.

EC fans adjust airflow to match IT load, cutting fan energy significantly.

Warmer chilled water improves chiller efficiency and increases free cooling hours.

A higher CRAH chilled water delta T reduces water flow and pumping energy.

A variable flow CRAH system with PICVs delivers stable control and lower pumping energy.

Energy efficient CRAH units for data centers, combined with efficient chillers, free cooling, and containment, help lower PUE.

Controllers modulate the valve and fan speed together to meet cooling and airflow demand, maintaining the desired CRAH supply air temperature.

Fan speed can be controlled by underfloor pressure or rack inlet temperature for precise, efficient CRAH temperature control.

Units rotate duty and start standby units automatically if a unit fails.

CRAH BMS integration and CRAH DCIM integration through SNMP, CRAH Modbus, or CRAH BACnet provide full visibility.

CRAH remote monitoring sends instant alerts for faults, high temperatures, and leaks.

Leak detection under raised floors provides early warning of water leaks.

Chilled water systems offer lower energy per kW of cooling at scale.

Refrigerant stays in the central plant, reducing risk in the white space.

Large coils and fan arrays deliver high cooling per unit.

No compressors in the data hall means fewer components to maintain.

Chilled water systems work seamlessly with free cooling chillers and economizers, enabling CRAH free cooling.

Without compressors, CRAH units run quieter than DX units.

Additional units can be added as IT load grows, which is ideal for colocation and hyperscale growth.

CRAH units need a central chiller plant with pumps and piping.

Chilled water piping in the data hall requires drip trays and leak detection.

For small rooms without a chiller plant, CRAC units are usually more practical.

Cooling depends on plant uptime, so redundancy is essential.

Chilled water pipes under raised floors need space planning to avoid airflow obstruction.

Compress India designs each CRAH installation to manage these limitations effectively.

Large corporate data centers use CRAH units for efficient, scalable cooling.

A CRAH for colocation data centers supports scalable, multi-tenant IT loads.

A CRAH for hyperscale data centers, often with fan walls, handles very high IT loads efficiently.

Data rooms in IT parks connect to existing central chilled water plants.

Large telecom facilities use CRAH units for reliable equipment cooling.

Control rooms in utilities and industries use CRAH units where chilled water is available.

Financial institutions rely on redundant CRAH systems for critical operations.

Hospital and lab server rooms connect to the building's chilled water system, making a server room CRAH unit a practical choice.

Vertiv CRAH units, including the Liebert CRAH range, are widely used in Indian data centers.

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

STULZ CRAH units are known for precision chilled water cooling solutions for data centers.

Rittal offers rack-based and room-level chilled water cooling solutions.

Mitsubishi Electric, through its Climaveneta range, offers chilled water precision cooling units.

Blue Star offers precision cooling solutions for data centers and server rooms in India.

Other manufacturers also offer chilled water precision units. Compress India recommends the best-fit brand for your project.

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

Filters are replaced regularly to maintain airflow.

Chilled water coils are cleaned to maintain heat transfer.

Control valves and actuators are checked for correct response and leaks.

Humidifier components are inspected and replaced as needed.

Sensors are calibrated and leak detection systems tested.

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

Causes: low chilled water flow, high water temperature, fan failure, or airflow issues.

Solution: Check water supply, valves, fans, and airflow management.

Causes: clogged strainers, pump issues, or incorrect balancing.

Solution: Clean strainers, check pumps, and rebalance flow.

Causes: chiller issues or high plant load.

Solution: Check chiller operation and plant capacity.

Causes: actuator motor failure, wiring faults, or valve blockage.

Solution: Repair or replace valves and actuators.

Causes: pipe joint leaks, condensation, or drain blockages.

Solution: Repair joints, improve insulation, and clean drains.

Causes: damaged insulation or humid conditions.

Solution: Repair insulation and vapour barriers.

Causes: poor airflow management or missing blanking panels.

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

Causes: EC fan motor or electronics failure.

Solution: Replace fans. Fan arrays maintain redundancy during repair.

Replacing old fans with EC fans improves efficiency and airflow control.

Facilities with a chilled water plant can replace DX CRAC units with CRAH units to improve efficiency.

Containment improves cooling efficiency and removes hot spots.

Upgrading to PICVs and modern controllers improves control and reduces pumping energy.

Increasing chilled water temperatures, with suitable coil upgrades, improves chiller efficiency and free cooling.

Higher capacity units cost more. Dual coil, dual cooling, and high-temperature designs add to the cost.

Chilled water piping, valves, drip trays, leak detection, electrical work, and commissioning form part of the installed cost.

Brand, capacity, number of units, redundancy, containment, controls, and chilled water plant scope all affect the final price.

Share your IT load and facility details with Compress India to receive an accurate CRAH unit quotation.