Reduction of operating costs

Circulating units (also known as split units) only cool the air in a room subjected to thermal stress and, consequently, rely on the continuous and operationally costly use of a mechanical cooling system. By contrast, our units with free cooling exploit freely available cooler outside air, thus reducing the operating time of the mechanical refrigeration system.

Outside air temperatures in Central Europe rarely exceed target temperatures in rooms under high thermal stress (e.g. server rooms). Our air conditioning units with free cooling use this outside air to reduce the operating times of mechanical refrigeration systems in Germany to approximately 7% of the service life (data pursuant to DIN 4710, Frankfurt/Main) and, therefore, considerably lower operating costs when compared to split units. Added to this is the output control of fans for supply and exhaust air relative to the thermal stress and outside air temperature involved.


Sample calculation

You have a technical premises with a cooling requirement of 15 kW. Our Slim Line Q15 is the ideal heat dissipating unit in this respect.


The following electrical power requirement per annum is calculated across the entire temperature range (see below for calculation details):

  • Circulating/Split unit: 40 550 kWh
  • Slim Line: 9 671 kWh


This is equivalent to a saving of approx. 76%. The following operating costs are calculated at an electricity price of €0.30 / kWh:

  • Circulating unit: €12 165 per annum
  • Slim Line: €2 901 per annum


Saving: €9 264 per annum

Saving with free cooling

The histogram indicates the distribution of hours in a year for the outside air temperature (location: Frankfurt/Main). Orange indicates the temperature range in which the mechanical refrigeration system of a Slim Line Q15 is active because free cooling is inadequate. Also marked is the sum of the temperature-dependent power requirement of the compressor and controlled fans for the Slim Line Q15 (green) and a 15 kW circulating unit with an external condenser (yellow).


The drop in the power requirement of the Slim Line unit after deactivation of the refrigerant compressor for outside air temperatures below 22 °C is clearly discernible, while the circulating unit consumes an almost constant output for the refrigerator and circulation fan in this context.

Reduce energy consumption with our IT climate solutions

Total energy consumption arising from use of the mechanical and free cooling systems and powering both fans is indicated in the diagram for the relevant temperature range (green). The requirement of a circulating unit with an identical refrigeration system (yellow) is also indicated.