CyberAir 3PRO CW

Innovative chilled water air conditioner for data centers

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The benchmark of flexibility and energy efficiency

The CyberAir 3PRO CW controls the conditions in the data center with the utmost precision, reliability and energy efficiency. Because STULZ technology leads the field, it can exploit potential savings to the full while still ensuring maximum reliability. No matter how different data centers may be, the CyberAir 3PRO CW is a chilled water air conditioner both flexible and made to measure: it is available in 11 sizes with various air conduction methods.

Data Center
Data Center
Our units are designed for highest requirements and maximum reliability
Small, medium & large rooms
Small, medium & large rooms
Precision air conditioning units for low to high heat loads
Optimized for air conditioning particularly large data centers
Free Cooling
Free Cooling
Maximum potential savings by using cool outside air

Product Overview

At a glance

Most important benefits

  • Maximum cooling capacity with a minimal footprint
  • Highly efficient air conduction (Airflow Efficiency Ratio)
  • Maximum potential savings with Indirect Dynamic or Direct Free Cooling

Most important features

  • Chilled water air conditioning systems available with integrated and external fan unit
  • 2 cooling systems (CW, CW2), 11 sizes, various air conduction methods, different heat exchangers

Most important technical data

  • Cooling capacity (kW): 22 – 260
  • Air conduction: Upflow, Downflow, Downflow with outlet front/back/down
  • Maximum cooling capacity with a minimal footprint
  • Highly efficient air conduction (Airflow Efficiency Ratio)
  • Maximum potential savings with Indirect Dynamic or Direct Free Cooling
  • Optimized for operating conditions based on the ASHRAE recommendation
  • Flexibility for individual customer solutions
  • Highest EER values due to maximum size of heat exchangers and filter surfaces
  • EC fans of the latest generation reduce power consumption
  • Compact design facilitates chilled water air conditioner’s transport and installation
  • Individual unit tests at the STULZ test center
  • Available with integrated and external fan unit
  • 2 cooling systems (CW, CW2), 11 sizes, various air conduction methods, different heat exchangers
  • CW standby management, differential pressure control and filter control management
  • Control based on the supply air, return air, room air or server inlet temperature
Technical Data
Cooling capacity (kW)22 – 260
Air conductionUpflow, Downflow, Downflow with outlet front/back/down
Airflow volume (m³/h)7,500 – 46,200

Height (mm): 2,495 – 2,915

Widths (mm): 950 – 3,350

Depths (mm): 890 – 1,040

Cooling systemsChilled water (CW/CW2)

All details about CyberAir 3PRO CW

Energy efficiency & reliability

New size specifically for large and hyperscale data centers

ABR range

This size for chilled water air conditioners was developed to meet the requirements of large data centers while keeping an eye on efficiency and reliability. By maximizing unit dimensions, this new size delivers more cooling capacity per footprint and increases efficiency in large and hyperscale data centers.

Benefits of the ABR range

  • High cooling capacity per footprint
  • Minimum fan power consumption thanks to the reduced internal pressure losses
  • Optimized Energy Efficiency Ratio (EER)
  • Optimized Airflow Efficiency Ratio (AER) and therefore air conduction with maximum efficiency
  • Increased Free Cooling times of the chiller due to higher air and water temperatures
  • Optimization of air temperatures based on the ASHRAE recommendation
  • Reduced water flow rate and therefore lower overall power consumption of the system and lower investment costs as smaller hydraulic components can be used



Free Cooling

Two different Free Cooling methods are used, depending on how the outside air is used. If the outside air is conveyed directly inside the building, this is Direct Free Cooling. If the outside air does not penetrate the sensitive interior of the building, this is Indirect Free Cooling. Both methods offer advantages but entail certain challenges. We individually check which version best matches your needs, requirements, and intended use - and which solution provides you with the best value over the life of the system.


Direct Free Cooling

The CyberAir 3PRO CW precision air conditioning system with Direct Free Cooling air conditions Data Centers up to 90 % more economically than conventional compressor cooling systems. Direct Free Cooling exploits the potential of outside temperatures to air condition the data center using the cool outside air. Via the CyberAir 3PRO CW, the outside air, which has been treated by filter systems, gets directly into the server room.                                                 

CyberAir 3PRO CW units with downflow air conduction can be equipped with the FreeCool Plenum Free Cooling box. The FCP design with the dampers on top is a flexible construction that takes up no extra space for the chilled water air conditioner. With this option, Free Cooling is automatically combined with the chiller system's compressor cooling in three variable stages, to suit the outside temperature and cooling needs, ensuring that maximum savings are always exploited to the full.

Learn more about Direct Free Cooling

Indirect Dynamic Free Cooling

Indirect Dynamic Free Cooling from STULZ is the only system worldwide with automatic efficiency optimization. The dynamic switching operation and control reduces the compressor running time to a minimum and reduces the total energy consumption by up to 60%, taking into account all active components.

The system cools precisely and dynamically according to the current heat load. This means that only the required cooling capacity is ever generated by the chilled water air conditioner and there is no energy-intensive oversupply. Taking into consideration outside temperature and current heat load, the dynamic switching operation and control selects the optimum operating mode without a fixed Free Cooling start value.                                                         

More information

Project: Free Cooling for Paragon CC printing business

At Paragon Customer Communications STULZ keep the printing environment in optimum condition whilst ensuring high quality productivity for 500 personnel working within a critical printing workspace.                                                                                                                       
More information

Fans in the raised floor

Optimized unit design for maximum potential savings

The design of our units means that STULZ precision air conditioning units boast maximum EER values and the lowest AER (Airflow Efficiency Ratio) values, and therefore achieve air conduction with maximum efficiency. The AER describes the ratio of the fan power consumption to the airflow. ASR air conduction (fans integrated in the raised floor), in particular, hugely reduces fan power consumption by ensuring minimal turbulence and changes in airflow direction, for energy savings that you will notice straight away. 

Precise temperature regulation

Delta T

The air-side difference in temperature between the air inlet and outlet of server cabinets and air conditioning systems is known as ΔT. To ensure optimum operation and the greatest possible savings on running costs, it is vital that the ΔT of the air conditioning units is adapted precisely and efficiently to the ΔT of your server cabinets.

Our dynamic control enables ΔT to be adapted to changing IT requirements, ensuring maximum energy efficiency during operation.

Learn more in our blog-article "Delta T – The air-side temperature difference"

Temperature profile

Optimum supply air conditions for reliability and maximum efficiency

To cool your data center as efficiently as possible without compromising on reliability, ASHRAE has published a recommendation for the air temperature at the server inlet. We have been developing chilled water air conditioning units for mission-critical applications - where even tiny malfunctions can have serious consequences - for decades now. Not only that, we have always focused on energy efficiency, and because of this, the supply air temperatures of our units lie within ASHRAE's recommended range.

EC fans

RadiCal EC fans of the latest generation

Increased performance. Maximum energy efficiency. Quieter.

  • GreenTech EC technology
  • Significantly higher air output
  • Over 10% lower power consumption
  • Reduced noise
  • Optimized airflow
  • Improves the AER of CyberAir 3PRO CW units
  • Latest motor generation
  • Impellers made of high-tech composite material for increased fan power density
  • Long lifetime
Pressure independent control valve

Chilled water air conditioner with pressure independent 2-way control ball valve

CyberAir 3PRO CW can be equipped with a pressure independent control valve. Here always the full-load water flowrate is set as a setpoint. The valve regulates the required water volume depending on the load.

"Pressure independent" means that the consumer always receives the correct water flowrate and that the control accuracy does not depend on the position of the valve as well as the pressure conditions in the hydraulic system.

Benefits of the pressure independent control valve

  • Simple and fast valve layout depending on the required water flowrate
  • No throttles and control valves necessary
  • No lenghty and personnel intensive hydraulic adjustment
  • Stable and precise regulation in each load condition by firmly defined water flowrate
  • Water flowrate can be read out
  • Flexibly settable water flowrate

Related Blogposts

More information on this topic is available in the following blog article:

Use of pressure independent control valves in CW units

Standby management

We create redundancy in our air conditioning units, to provide you with the most reliable air conditioning possible. To do this, we install more units than are actually needed for air conditioning.

With the usual, passive form of redundancy, these units are only started up (automatically) if a unit that is running switches off due to a fault. With STULZ standby management, on the other hand, active redundancy exploits the potential of the EC fans. While the total airflow remains the same, the use of standby units per unit is reduced. The reduced airflow cuts fan power consumption and associated operating costs even further. In all, this measure not only lowers operating costs but also reduces overall noise. If a unit fails, the speed of all the fans of the other units increases.

Related Blogposts
More information on this topic is available in the following blog article:

Standby Management for CW units

Passive redundancy

With passive redundancy, the active air conditioning units continuously run at full load. The standby unit remains unused.

Active redundancy

STULZ standby management uses active redundancy to distribute reserve capacity evenly between all air conditioning units in partial load mode. If individual units fail or require maintenance, the remaining units automatically switch to controlled full load operation.

Complete System with chilled water generation

Combined efficiency from STULZ

Air conditioning solutions from STULZ offer synchronized overall systems that cool server rooms efficiently and reliably. For data centers, in particular, combining the CyberCool 2 chiller with the CyberAir 3PRO CW precision air conditioning unit is an investment in lasting quality, reliability and outstanding efficiency. You can find more information about our CyberCool 2 chiller here.

Control and monitoring
  • In-house developed controller for regulating and monitoring the air conditioning system
  • Autonomous controllers in every air conditioning module ensure maximum redundancy (no chain reaction if a module fails)
  • Optional sequencing with standby functions enables the individual air conditioning modules of a group to be used to a greater or lesser extent with the utmost flexibility
  • Central control of up to 20 air conditioning modules per data bus system is possible
Service and maintenance

As a company with locations across the globe, we offer everything you need in the extremely dynamic world of information technology – plus professional advice in the right place at the right time.

Our trained and experienced sales and service partners are located in over 140 countries. The resulting proximity to our customers allows fast response times. In addition, regular training courses and an active exchange of information ensure high quality and an extensive knowledge of all our products. This way, you can be sure your products are in the best hands and get the right maintenance – all over the world.

Locations worldwide


Test Center

In our state-of-the-art, 700-square-meter Test Center with its various climate chambers, we can perform a variety of tests on precision air conditioning units and chillers. During the development of the CyberAir 3PRO CW, we were able to test and optimize it under all climatic conditions encountered around the world.

In addition, we offer you the opportunity to book a witness test in our Test Center. This allows you to have the desired air conditioning system tested according to your exact specifications, creating transparency and providing you with information about your system’s performance and energy consumption.

More information


Climate. Customized.

From standard units to fully customized solutions

The ability to offer such a wide range to customers is the embodiment of our philosophy, "Climate. Customized.". Size, design, air conduction, system or control: CyberAir 3PRO CW is a model of adaptability and the room air conditioners can be precisely adapted to your individual requirements. In addition, a variety of options and equipment versions are available to achieve the optimum result.

Learn more about Climate. Customized.

Upflow, Downflow and Raised Floor

Downflow and Upflow versions

The design with integrated fans is available with standard Downflow (ASD) and Upflow (ASU) air conduction. Through further development and by optimizing the design, the units are now considerably more efficient than the chilled water air conditioner's previous version.

This can be witnessed in the noticeably higher Energy Efficiency Ratio (EER) and lower Airflow Efficiency Ratio (AER).

Raised Floor version

The Raised Floor (ASR) series promises even higher energy savings than units with fans on the raised floor. This model is equipped with an external fan box, and air conduction is specific to the unit. The fan box is installed under the unit, in the raised floor.

The resulting additional space in the air conditioning unit can be used for larger heat exchangers, resulting in a noticeably higher cooling capacity for the footprint. What’s more, positioning the fans in the raised floor means less turbulence and fewer changes in airflow direction. The result is ideal air conduction and therefore massively reduced fan power consumption (AER).

Various air conduction systems

Raised floor, air conduction: Front

Raised floor, air conduction: Front/Back/Down

High version, air conduction: Down

High version, air conduction: Displacement



Heat exchangers

Optimized heat transfer via high-quality chilled water air conditioners

In chilled water systems, the heat exchangers are the most important component and a guarantee of the best possible heat transfer. The heat exchanger system of the CyberAir 3PRO CW is continually being further developed and optimized for the latest data center applications. Different versions of heat exchangers are available, ensuring the precision air conditioning’s flexibility to satisfy every customer's specific requirements.

Benefits of the optimized heat transfer

  • Optimized cooling unit geometry
  • Reduced water and air-side pressure drops
  • Several versions for maximum flexibility

Special solution for modernized data centers

A special heat exchanger is suitable for operation at high air-side and low water-side temperatures - and therefore for data center modernization projects where old chillers will continue to be used for the air condition. This configuration enables supply air conditions in accordance with the ASHRAE recommendation.

Options for data center cooling

The numerous different options and possible equipment enable you to perfectly adapt CyberAir 3PRO CW chilled water air cooler units to your requirements.


  • Dual power supply with automatic or manual switchover plus option of UPS buffering of the controller
  • Pressure independent 2-way control ball valve
  • C7000 Advanced user interface
  • C7000 AT controller with display of airflow rate, total cooling capacity, unit EER
  • Indirect Dynamic Free Cooling for CW2
  • Intake plenum for Direct Free Cooling
  • Electric heater, one to three stages or continuous
  • Reheating of hot water
  • Continuous steam humidification
  • Raised floor stand in various heights
  • Louver dampers
  • Duct fitting with pocket filter attachment F7, F9
  • 3-way CW valve
  • Smoke and fire alarms
  • Suitable for connection to all common BMS systems, RS485 and RS232 interface for direct connection to a BMS
Cooling Systems

STULZ offers individual system solutions adapted precisely to your project requirements.

CW system

CW system: Liquid cooled system

CW units manage without a refrigerant circuit of their own, but require separate chilled water generation. The room air conveyed by the fan flows through the direct cooling unit, which transfers heat to the water/glycol mixture. A chiller removes the heat from this water/glycol mixture. The air conditioning unit and the chiller are connected to one another by a closed water/glycol circuit.

CW2 System

CW2 system: Liquid cooled system with built-in redundancy

High-reliability systems frequently require a second, independent chilled water supply. Therefore, in the CW2 system two redundant CW systems are integrated in a single air conditioning unit, saving valuable space in the Data Center.


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