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Potential savings with Direct Free Cooling

Direct Free Cooling enables the potential of cool and moderate outside temperatures to be used over long periods with maximum efficiency anywhere in the world. In temperate zones north and south of the equatorial zone, in particular, users can benefit from the advantage of low consumption.

Air conditioning with treated outside air

As the name suggests, Direct Free Cooling is the most direct Free Cooling method. To put it simply, it can be compared to opening a window. The outside air gets directly into the room but is additionally treated by filter systems. Despite this, the use of Direct Free Cooling does depend on the quality of the outside air. In other words, wider tolerances have to be allowed for temperature and humidity.

Advantages of Direct Free Cooling at a glance

  • Maximum energy efficiency thanks to the direct use of Free Cooling
  • Excellent system scalability – no hydraulics (pipework, pumps, valves)
  • Lower investment costs compared with conventional Indirect Free Cooling systems
  • Much lower energy requirement than all conventional systems

Operating modes

Free Cooling is automatically combined with compressor cooling in four variable stages to suit the outside temperature and cooling needs, ensuring that maximum savings are always achieved:


1. Free Cooling

  • Outside air damper open
  • Outside air flows through the filter straight into the unit and then into the data center
  • The compressor of the chiller system remains off, completely saving the cooling energy normally required

2. Extended Free Cooling

  • Outside air damper open
  • Fan speed control increases the airflow, ensuring a constant cooling capacity and therefore additionally lengthening the period when Free Cooling can be used
  • The compressor of the chiller system remains off, completely saving the cooling energy normally required

3. Mixed mode

  • Outside air damper open
  • Fans deliver the maximum airflow
  • Compressor is switched on

4. Compressor mode

  • The outside air damper remains closed, and no outside air is used for cooling.
  • The air conditioning unit cools solely using the chiller system's compressor.

Benefit from our experience

STULZ has already accomplished numerous Free Cooling projects around the world. That's why we are perfectly aware of the requirements of different countries and continents – and always have precisely the right solution for you: our scalable air conditioning systems are perfectly adapted to the specific parameters of your location, reliably, individually and precisely.

It's important to check which type of Free Cooling best matches your needs, requirements, and intended use – and which solution provides you with the best value throughout the system's life. If you do not want any outside air to get into the sensitive interior of the building, Indirect Free Cooling is the most beneficial solution. Here, the quality of the outside air is irrelevant. Indirect Dynamic Free Cooling from STULZ offers the greatest potential savings.

Indirect Dynamic Free Cooling